RS-25:

The SSME has provided safe flight for the Shuttle’s eight and a half minute ride to orbit since debuting with the Columbia during her launch in 1981. The engines proved their worth with only one major malfunction during its flight history, namely STS-51F (ME-1), resulting in a safe Abort To Orbit (ATO).

The RS-25D is capable of achieving 400,000 lbs of thrust with an ISP of 453 seconds in a vacuum, or 363 seconds at sea level. The engines consist of over 50,000 parts and could be reused up to 20 times during their role with Shuttle.

Following the decision to retire the Shuttle once the International Space Station had been assembled, the engines were set to live on with the Ares I Upper Stage. However, problems with the requirement for air-starting the engine for second stage flight altered NASA’s direction towards the J-2X.

With no future role for the RS-25s, NASA’s Transition Control Board (TCB) – a body that was tasked with redirection of agency assets to the Constellation Program (CxP) – directed the shutdown of engine production capabilities in 2007. At the time it was determined that only four new engines would be required to satisfy the needs for the remaining Shuttle missions.

With the Constellation Program already struggling with budget and schedule concerns, a NASA Authorization Act in 2008 placed a temporary hold on the complete shutdown of RS-25 fabrication assets – mainly from the standpoint of spare hardware availability – as evaluations took place into short-term and long-term Shuttle extension possibilities.

Thanks to the reusability of the SSMEs, only one additional “full engine” would have been required, had a two year extension – past its original 2010 end date – occurred during the evaluations. In the end, only the Contingency Logistic Flights (CLFs) of STS-133 and STS-134 – along with the addition of STS-135 – were added to the manifest.

One lesser known option for continuing to use the RS-25s came during development of the Ares V Heavy Lift Launch Vehicle (HLV).

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The Ares V baseline consisted of a 10 meter core stage with six RS-68B engines, and two 5.5 segment solid boosters derived from the Ares I Program.

However, with the Constellation Program looking for additional margin on lunar exploration missions – along with continued efforts to save money – managers returned to some of the original evaluations into the HLV via the ESAS (Exploration Systems Architecture Study) in 2005.

The ESAS discussed a range of Cargo Launch Vehicles (CaLVs) during the early days of the Vision For Space Exploration (VSE), with CxP referencing that study as part of their interest in switching Ares V’s baseline towards an 8.4m core with five or six expendable SSME’s, two five segment SRBs, and two J2-S engines on the upper stage.

The marriage between refining Ares V to a previous ESAS option also moved the vehicle closer to a more powerful HLV known as the “Magnum”, as outlined in the AIAA Joint Propulsion Conference Document from 2005.

However, the Ares V discussions focused on the potential use of five or six RS-25Es – the expendable version of the SSME – on the core stage.

While the Ares V didn’t survive the cull of the Constellation Program, data from the potential switch to RS-25s on the HLV likely fed into the RAC (Requirements Analysis Cycle) effort that was tasked with finding the best baseline for the new Space Launch System (SLS) rocket – the HLV that is now the focal point of NASA’s latest Beyond Earth Orbit (BEO) drive.

One key element of the Ares V study noted the the RS-25s may be better suited than RS-68s for mitigating the plume impingement and base heating issues that were an issue with the Ares V.

In a cluster of engines, the nozzle must withstand both the heat from its own exhaust in addition to the outside exhaust plumes of the other engines in the cluster.

The study – available on L2 – noted that exhaust plumes of six RS-68 engines, combined with the two SRBs, interact to reduce the efficiency of the engines, and cause extreme heating on the base of the core stage.

As such, the study claimed the regenerative nozzle of the RS-25 held an advantage over the ablative nozzle on the RS-68s, by providing more resilience, adding the regenerative nozzle protects both the inside and the outside of the nozzle, versus the ablative nozzle which is designed to deal with heat from only the inside.

Numerous other factors saw the RS-25s selected as the engines for the SLS core stage, not least the law of the 2010 Authorization Act that ordered NASA to select a vehicle that used both Shuttle and former Constellation Program hardware, confirming the engines would live on in their new role after the Shuttle Program ended.

All nine of the last SSMEs to fly with the Space Shuttle performed admirably, with Discovery flying Main Engine 1 (ME-1) – serial number 2044, ME-2 – 2048 and ME-3 – 2058 during her final mission, STS-133.

For Endeavour’s swansong, ME-1 – 2059, ME-2 – 2061, and ME-3 – 2057 helped begin the flight phase of the successful STS-134 mission, while Atlantis closed out the Space Shuttle Program, flying with engines ME-1 – 2047, ME-2 – 2060 and ME-3 – 2045 during STS-135.

A total of 15 RS-25Ds left the Kennedy Space Center (KSC) for their new role, arriving at the Stennis Space Center in 2012.

While testing has been ongoing on the J-2X Upper Stage engine, Stennis engineers are now working on building and installing a new 7,755-pound thrust frame adapter for the A-1 Test Stand, in order to enable testing of the RS-25s ahead of their role on SLS’ core.

The reason for the new adaptor relates to the requirement of different types of engines. On the test stand, the adapter is attached to the thrust measurement system, with the engine then attached to the adapter, which must hold the engine in place and absorb the thrust produced during a test, while allowing accurate measurement of the engine performance.

The adaptor that is currently installed on the A-1 Test Stand is specific for the J-2X – an engine capable producing 294,000 pounds of thrust. It can’t be used for the RS-25, given that engine is much more powerful, with the ability to produce approximately 530,000 pounds of thrust.

The design – produced by NASA, Lockheed Martin Test Operations Contract Group and Jacobs Technology – took several considerations into account, such as specific stresses on the equipment as an engine is fired and then gimbaled during a test.

“It’s a challenging project,” noted Kent Morris, RS-25 project manager for Jacobs Technology. “It’s similar to the J-2X adapter project, but larger. It will take considerable man hours to perform the welding and machining needed on the material. The material used for the engine mounting block alone is 32 inches in diameter and 20 inches thick.”

The installation is set to take place in November, once the Test Stand has completed J-2X gimbal testing.

SLS will naturally evolve after the opening flights of the Block I SLS, with SSME contractor Pratt & Whitney Rocketdyne (PWR) set to produce RS-25E engines for the rest of the SLS’ lifetime. The RS-25E is expendable and thus requires less long-life hardware items, in turn making it cheaper to produce.

(Images: Via L2 content from L2′s SLS specific L2 section, which includes, presentations, videos, graphics and internal – interactive with actual SLS engineers – updates on the SLS and HLV, available on no other site. Other images via NASA)

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SLS Progress:

With the Space Launch System deep into its pre-PDR evaluations, the Heavy Lift Launch Vehicle (HLV) continues to avoid the problematic technical issues suffered by the rocket it technically replaced, namely the Ares I from the now-defunct Constellation Program (CxP).

While Ares I had managed to get through the PDR stage prior to its demise, major SLS elements – such as the Core Stage – are already fast approaching the point of maturity Ares I’s Upper Stage had achieved.

As such – and despite a compressed schedule to make its debut launch target in 2017 – SLS is on track and continues to enjoy several months of schedule margin.

Of course, as with any rocket, SLS’ development thus far has not been trouble-free, with engineering teams successfully mitigating problems such as a required change to the slosh baffle design on the core stage.

As noted in L2′s SLS Development Update Section, engineers are also looking at the design of the booster nose cones, due to an aeroacoustic loading issue – in the transonic flight region – impacting on the booster/core attach points, per evaluations.

Initial information points to potentially changing the nose cone design to that seen on boosters used by Ariane 5, or indeed the cone design currently portrayed by ATK’s Advanced Boosters, in order to mitigate the issue.

Notably, per all recent information, none of SLS’ challenges have resulted in a major concern on its report cards, unlike Ares I’s troublesome childhood.

A huge amount of work has already taken place at the pre-PDR level, with some elements of the Core Stage already eyeing the next big milestone – the Critical Design Review (CDR) in 2015.

The depth of the PDR can be seen via one status update that noted one department’s “data pack” consisted of over 300 documents – 200 of which were created for the Interim Cryogenic Propulsion Stage (ICPS) by Boeing/United Launch Alliance (ULA) – before being sent for review at five NASA centers.

Per L2 information, the review of that PDR data pack – for the Spacecraft and Payload Integration Office (SPIO) – is now complete, with the reviewers adding what are known as candidate Review Item Discrepancies (RIDs).

A series of meetings have now begun to evaluate and categorize the RIDs, via a complex process that will last as late as June 14. The disposition of the RIDs will be reviewed by the SPIO PDR Pre-Board on June 20, and final approval of all RID dispositions will be completed by the PDR Board on June 27.

Following the Board meeting, document developers will begin the process of implementing the RIDs in the documents.

Meanwhile, the data pack for the SLS PDR was released to reviewers on Friday (May 31). The reviewers have until June 28 to submit candidate RIDs.

The formal “kick off” for the SLS PDR is on track for June 18-19.

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Once the PDR is complete, all SLS elements will progress towards the CDR. Two more review milestones will follow ahead of the debut launch of the SLS, with the Design Certification Review (DCR) followed by the Flight Readiness Review (FRR) – the latter ensuring all open items from DCR are closed out prior to flight.

Evolved SLS via the PDR:

Per L2 information, one of the documents in the SLS PDR data pack is the “Evolvability Report”, which is a technical evaluation for potential development paths by which the Block 1 SLS can be “evolved” to its full capability, as required by Congress.

SLS will initially launch as a Block 1 vehicle, with a 70mT capability, conducting the opening salvo of Beyond Earth Orbit (BEO) adventures, such as Exploration Mission -1 (EM-1), an uncrewed mission to send Orion on a test flight around the Moon, and Exploration Mission -2 (EM-2). which involves sending a crewed Orion on a mission to meet up with a captured asteroid in the vicinity of the Moon.

By the mid-2020s, SLS will evolve to a Block 1A vehicle with a 105mT capability, using Advanced Boosters, utilizing either Solid or Liquid fueled options. A Block 1B option may also be available, with a 118mT capability, as explained later in the article.

The final evolution will be to the Block 2 SLS, which is classed as the flagship launch vehicle for crewed missions to Mars.

While the Evolvability Report is nothing more than a technical evaluation for decision makers – and does not represent any actual decisions by NASA for future SLS development – it does provide an interesting insight into SLS’ growth options.

Option 1 begins with development of the Advanced Boosters, followed by the use of the J-2X Upper Stage, the increase to five RS-25E engines on the Core Stage, prior to the addition of a five meter diameter Cryogenic Propulsion Stage (CPS).

Option 2 also begins with development of the Advanced Boosters, followed by the five meter CPS, then the J-2X Upper Stage, and finally move to a five engine Core Stage.

Option 3 takes SLS along a different path, with the development of a Dual-Use Upper Stage (DUUS – pronounced “Duce”), followed by development of the Advanced Boosters.

Per L2 information, each of the options were evaluated for their “mission capture” attributes, or how soon each of the Design Reference Missions (DRM) maintained by the Human Architecture Team (HAT) are enabled by the increased capability of the SLS via each improvement – such as the increase in payload capability when the Advanced Boosters debut with the HLV.

While the HAT are still working on the future missions, from EM-3 onwards, the SLS Evolvability Report concludes that Option 3 achieves the best “mission capture” results, followed by Option 2.

The finding adds yet more weight to source notes over recent years that the J-2X is by no means assured of a role with the SLS.

Expanding on the DUUS option, this stage – driven by up to four RL-10 engines – would be tasked with completing the ascent phase of the SLS after Core Stage burnout, before then operating as an In-Space Stage – hence, the “dual use” tag – to conduct the Trans-Lunar Injection (TLI) burn for an Orion spacecraft, coast to the Moon and conduct the Lunar Orbit Injection (LOI) burn.

Then, after Orion separates, it would conduct a disposal maneuver to crash the stage into the Moon.

The DUUS was studied in three possible configurations, namely the 8450, 8455, and 8463 models. Each configuration consists of an 8.4-meter diameter LH2 tank and LOX tank – the latter with diameters of 5.0, 5.5, and 6.3 meters, respectively.

The 8450 model would be able to take advantage of existing manufacturing capabilities for the construction of the LOX tank, as such this model is expected to be the cheapest to produce.

However, the 8463 model is the shortest of the three configurations, which would allow for the optimum payload height during integration processing inside the Vehicle Assembly Building (VAB).

Follow on information notes the advantages of an 8.4m DUUS on an 8.4m core includes the potential for a common bulkhead between LOX and LH2 tanks, and – in addition to the high efficiency engines – this should equate to less stage dry mass, resulting in additional payload up-mass capability.

Documentation from 2012 also pointed towards the evaluations into using the RL-10 driven stage, showing the SLS Block 1B, using Five Segment Boosters, resulting in an up-mass capability of 118mT to Low Earth Orbit (LEO) and 43mT to Beyond Earth Orbit (BEO).

The information also shows the SLS Block 2 – again with the 8.4 meter diameter 4xRL-10 stage – with Advanced Boosters, allowing for an up-mass capability of 155mT to LEO and 61mT to BEO.

While the forward path for evaluating all of the options will result in no immediate decisions, the “Duce” is already being cited as a large money-saver, not least because it would likely allow SLS to remain with its four RS-25E’s on the core stage, removing the redesign requirements to move to a five engine core when SLS evolves.

Further articles will follow during the PDR process.

(Images: Via L2 content from L2′s SLS specific L2 section, which includes, presentations, videos, graphics and internal – interactive with actual SLS engineers – updates on the SLS and HLV, available on no other site. Other images via NASA and ULA)

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SLS SMAT:

Continuing the heritage of testing future launch vehicles at the scale model level, NASA engineers have test fired scaled versions of rockets to gain data on the acoustic environments endured during ignition and launch.

The primary source of the acoustic field is the fluctuating turbulence in the mixing region of the rocket exhaust flow – known as Engine Generated Acoustics.

Engine generated noise is a function of the exhaust flow parameters, launch stand configuration, and to a lesser extent atmospheric conditions.

Preliminary estimates of the engine generated acoustics at a specified location on the vehicle can be determined by scaling measured acoustic data from previous launch vehicle programs, taking into account the above mentioned flow, configuration, and atmospheric parameters.

A better definition of the lift-off acoustic environment can be determined from hot fire testing of dynamically scaled models of the launch vehicle and stand.

During the Space Shuttle development program, a 6.4 percent scale model of the launch vehicle, propulsion system, launch stand, and exhaust duct system with water suppression was used to refine the analytical/scaling estimates of the lift-off acoustic environment.

The resulting data provides a very useful template for the full scale rocket, although final verification of the environment is only fully provided by full static firings or launches of the actual vehicle.

Notably, the debut launch of the Space Shuttle Program (SSP) – with Columbia on STS-1 – showed the importance of understanding the acoustic environments, as the orbiter’s heat shield was damaged when an overpressure wave from the SRBs caused a forward RCS oxidizer strut to fail. Her body flap was also pushed five degrees out of position.

The subject was also raised during STS-129′s Flight Readiness Review (FRR), as a potential issue with a very small area of the orbiter – known as a stinger attach point between the RCS and OMS Pod – raised concerns that recent acoustic environment analysis of the Space Shuttle Main Engines (SSMEs) during ignition could cause stressing that potentially leads to cracks in the attach pins/stinger.

Although those concerns were based on old and overly conservative data, managers showed their usual due diligence in gathering an array of updated information, via new computational models, borescope inspections on the fleet, and the installation of sensors in the area in question – all of which would be used to completely allay the potential fear of life fatigue on the stinger.

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Notably, the FRR presentations noted they lacked key historical data, given the 6.4 percent model tested during the 1970s only fired motors that mimicked the Solid Rocket Boosters and not the SSMEs, while Main Engine Ignition (MEI) Acoustic & SSME Ignition Overpressure (IOP) Environment data was classed as “continually evolving” during the 30 years of the program – leading to the concern ahead of STS-129.

The vehicle that was set to replace the Space Shuttle, Ares I, also underwent IOP testing – with the Ares I Scale Model Acoustics Test (ASMAT) tested during 2010.

Numerous tests, each using a different pad configuration – such as with and without water bags within the launch mount – were conducted at MSFC.

Quick look test results indicated that the overall noise levels measured on the vehicle were within predicted ranges and the data compared favorably between the firings. However, Ares I was cancelled shortly after the ASMAT firings.

With the SLS now providing the role of NASA’s flagship launch vehicle, the Heavy Lift Launch Vehicle (HLV) will enjoy its turn on the test stand for the acoustic environmental tests – known as Scale Model Acoustic Test (SMAT).

Work begin in 2012 at Marshall’s test stand 116, with the construction of a working water-based sound suppression system.

“This water system will be used during the planned hot fire testing series that is planned for SMAT, which utilizes small-scale solid rocket Boosters and Lox-Hydrogen thrusters,” noted L2′s rolling SLS updates.

“Based on discussions with NASA/KSC Ground Systems Development and Operations (GSDO) engineers, MSFC is satisfied that this properly represents the water flow rates and coverage of the full-scale system and will meet the test needs for SMAT.”

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As with the tests on the previous vehicles, the data will provide a good baseline ahead of the actual SLS firing into life later this decade.

Notably, the SMAT will involve the most technically advanced sub-scale rocket used on such a test.

“Ignition overpressure (IOP) is a significant transient low-frequency pressure event caused by the rapid pressure rise rate of the solid rocket motor,” opened an extensive presentation on the SMAT (L2). “Lift-off acoustics (LOA) noise is caused by the supersonic steady jet flow interaction with surrounding atmosphere and launch complex, persisting for 0-20 seconds as the vehicle lifts off.

“Scale Model Acoustic Test (SMAT) objectives: Verify predicted LOA environments, obtain data to update the lift-off acoustic environments. Verify predicted IOP environments, obtain data for use in IOP analytical models for updated environments, and improve IOP analytical models.

“Verify SLS deflector design. Characterize Ground Acoustic (GA) environments, provide data to support GA environment predictions. Obtain Spatial Correlation (SC) data for use in vibro-acoustic models. Obtain data for Computation Fluid Dynamics (CFD) validation, and evaluate water sound suppression systems, determine water suppression attenuation.”

Obviously, engineers won’t be able to literally scale down the SLS’ RS-25 main engines or five segment SRBs, so alternative motors will be used on the SMAT model.

As such, two Rocket-Assisted Take Off (RATO) motors will simulate SLS boosters, with the test requirement calling for the motors ignite simultaneously, as the SRBs would during launch.

Testing has already begun on the small thrusters that will provide the role of the four RS-25 liquid main engines on the core.

A single thruster – similar to vintage hardware originally designed in the 1960′s and tested during the Space Shuttle program – successfully met all test objectives during Phase I scale model acoustic testing last year at Marshall’s Test Stand 115.

Fabrication then began for a “fourthruster cluster” set, mirroring the four RS-25s that will power all versions of SLS’ core stage.

“Hot-fire testing was initiated for the thrusters that will simulate the Core Stage Engines for the Scale Model Acoustic Test (SMAT). All four thrusters have been tested together for the first time in a single cluster in the same configuration that will be used for the Core Stage of the SMAT model,” added SLS’ rolling update section (L2).

“Testing is being conducted at Test stand 115 in the Marshall Space Flight Center (MSFC) East Test area. The first start ignition test was conducted on March 7, 2013. Two low thrust main stage tests were conducted on March 8, 2013. All test hardware is in excellent condition so far and (will continue testing during the Spring).”

When the actual SMAT model is completed and integrated on the test pad, a number of tests can be expected, not least because the maximum lift-off acoustic environment during an SLS launch will not be endured in the vehicle starting position, but at some elevation above the Mobile Launcher.

As such, tests will probably attempt to simulate a lift-off, without the SMAT model actually launching.

For the Ares I Scale Modelling Acoustic Tests, the vehicle model was set at a number of fixed elevations for individual test firings, these being 0, 2.5, 5.0, 7.5, and 10.0 feet. Based on the scale of the ASMAT, these distances corresponded to full-scale elevations of 0, 50, 100, 150, and 200 feet.

Also, as expected, the test vehicle will be heavily instrumented, with five primary instrumentation suites resulting in over 325 sensors on the SMAT rocket.

It will be outfitted with B&K 4944-B microphones, pressure transducers on the tower/mobile launcher. It will include far field measurement devices, accelerometers, thermocouples and strain gauges on vehicle, thermocouples, flow meters and chamber pressure instrumentation.

The first test fire is expected to take place either in the summer of fall of this year.

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SLS Design Change:

NASA’s new Heavy Lift Launch Vehicle (HLV) remains on track for its debut on Exploration Mission -1 (EM-1) to the Moon in 2017, after successfully transitioning from the joint System Requirements Review (SRR) and System Definition Review (SDR) to the key PDR stage of development.

While the design of the vehicle – such as the appearance, or Outer Mold Line (OML) – are all-but baselined into what spectators can expect to see roaring off Pad 39B in the second half of this decade, a large amount of fine-tuning is taking place, via the NASA and contractor engineering teams at the Marshall Space Flight Center (MSFC).

The prime contractor is Boeing, who’s involvement with the monster rocket ranges back to prior to the official announcement by NASA, confirming the SLS configuration as a Shuttle Derived (SD) HLV.

As part of the fine-tuning process, Boeing engineers recently recommended a design change relating to the heatshields surrounding the four engines on the core of the SLS. The HLV will initially launch with four Pratt & Whitney Rocketdyne (PWR) RS-25Ds, donated by the Space Shuttle Program (SSP), prior to moving to the non-reusable version, known as the RS-25E.

As seen with the Shuttle orbiters, a dome of Thermal Protection System (TPS) tiles and a ring of white thermal blankets surrounded each of the SSMEs on the aft, with only the Nozzle visible from the outside. This was known as the “eyelid and dome” hardware, something that had remained relatively unchanged during the life of the SSP.

The “eyelid” is the rigid spherical portion attached to the engine nozzle, whereas the “dome” is the portion attached to the orbiter. The dome has a rigid conical portion with TPS tiles on it and a flexible blanket portion with a seal that is pressed against the eyelid with 48 spring cans.

This was a very complex piece of hardware, requiring a lot of refurbishment between flights, one reason it was usually seen undergoing work on the Orbiter Processing Facility (OPF) floor between flights, during the period the SSMEs had been removed from the vehicle.

While one obvious reason for the change could be assumed to the fact SLS core will not be returning home for reuse – at least removing the re-entry considerations – even the orbiter’s engine heat shield design was driven not by the vehicle’s return, but instead by the launch environments.

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As such, there are a lot of factors that allow this change to take place. Primarily, it is due to the improvement in flexible thermal protection materials over the 40 years since the orbiter was developed, while the move will also save some weight on the aft of the vehicle.

“The Boeing team is recommending replacement of the heritage orbiter ‘eyelid and dome’ engine heat shields with a flexible blanket similar to what is used for the Solid Rocket Booster nozzles and other expendable launch vehicles,” noted one of the numerous updates on L2′s SLS rolling updates section, confirming the change.

“The blanket design will save approximately 700 pounds in weight while being easier to produce, assemble, and install. The blanket will use the same attachment scheme on the engine nozzle and core base heat shield as the heritage design.”

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The flexible thermal blankets will be similar to those used around the RS-68 nozzles on the Delta IV, with additional knowledge available from their use on the aft skirt of the Solid Rocket Booster.

As such, engineers will have a database of understanding on how these blankets perform during launch, including any potential challenges – such as that observed during STS-116′s ascent.

Discovery’s launch was nominal. However, long range trackers – used by NASA’s Systems Engineering and Integration (SE&I) group – provided an amazing close up video (available on L2 – LINK) of the two booster nozzles with their blankets vibrating under the intense atmosphere of the exhaust.

The left booster, however, showed its “curtain blanket” was “flapping” during ascent, after becoming partially detached.

It has been noted by sources that the behavior of the blankets is something that will be assessed to make sure the ignition overpressure (IOP) does not cause the blanket to contact the engine powerhead components.

Testing may also be required if the environment at the base of the SLS core is worse than what the existing materials have been certified for. Even if the thermal environment is not worse, the debris or pressure environment may be a relevant area of evaluation.

The design change will debut during the test firings at the NASA Stennis Space Center (SSC). These firings will be known as “Green Run” testing – given they are carried out with the first two flight articles. Since they are the flight articles, using real RS-25 engines, they will have these blankets installed.

(Images: Via L2′s SLS specific L2 section, which includes, presentations, videos, graphics and internal – interactive with actual SLS engineers – updates on the SLS and HLV, available on no other site. Lead image SLS rendering used used with permission from terrabuilder.com and Boeing.)

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Atlantis:

Although Atlantis is not yet fully prepared for her retirement, the Kennedy Space Center (KSC) teams are looking to turn over OPF-1 to an unnamed commercial company, who – like Boeing and their CST-100 spacecraft taking up residency in OPF-3 – will breath new life into the facility now the Shuttle fleet has fallen silent.

Bart Pannullo, NASA Vehicle Manager for Space Shuttle Transition and Retirement processing, noted that the original plan was for Atlantis to be towed in mid-November out of the OPF and down Kennedy Parkway to the Kennedy Space Center Visitor Complex, where work is in progress to prepare the new facility where the orbiter will be displayed from early 2013.

However, Mr Pannullo added that there remained the possibility that Atlantis would have to vacate OPF-1 and go back to the VAB again, in order to make way for a commercial customer.

“If we turn the OPF over to another customer, we’d put Atlantis in the VAB until Endeavour rolls to the MDD (Mate Demate Device),” he noted in an interview with NASASpaceflight.com in April, with that plan now initiated.

No commercial companies have stepped forward with their claim on OPF-1, likely under an embargo agreement, as was seen ahead of Boeing’s deal with NASA and Space Florida for taking over OPF-3′s facilities for their CST-100 capsule that is one of the contenders to transport NASA astronauts to the International Space Station (ISS) in the second half of this decade.

Planning documents (L2), under the 21st Century Spaceport concept, have shown various commercial vehicles using KSC facilities, including a fleet of Sierra Nevada Corporation (SNC) Dream Chasers – another commercial crew contender – being processed inside a clean floor OPF.

Official responses to the slides have noted such representations should be classed as notional only.

Pending acceptable weather, Atlantis will be rolled to High Bay 4 (HB-4) of the VAB, where she will remain protected by the giant building.

There she will become the new neighbor for Crawler Transporter 2 (CT-2), which is located inside High Bay 2 (HB-2), where it is undergoing modifications into a “Super Crawler”, capable of transporting the Space Launch System (SLS) to Pad 39B – (L2 Link to SLS Super Crawler Section).

Atlantis herself has contributed toward the SLS Heavy Lift Launch Vehicle (HLV), via the donation of large elements of her orbiter Main Propulsion System (MPS) and Space Shuttle Main Engines (SSMEs – RS-25Ds).

In the end, Atlantis and Endeavour provided the majority of the components that will be used by the SLS test program, whereas Discovery remained mainly intact as the “Vehicle Of Record”.

Sporting three RSMEs – as opposed to SSMEs, following the Program Requirements Control Board (PRCB) decision to protect all flight-able SSMEs for the SLS program – Atlantis will have a similar appearance to how the public saw her when she returned home from her highly successful STS-135 mission, the flight that closed out the 30 year career of the Shuttles.

Although the SLS had not been selected at the time, the PRCB Change Request presentation (available on L2 – LINK) noted direction from the Space Shuttle Program (SSP) to roadmap the ability to keep the engines, and replace them with replicas for when the retired vehicles go on display at their exhibitions.

The RSMEs simply consist of a scrap – but cosmetically repaired – nozzle, with an adaptor to install it into the aft of the retired orbiter were produced by SSME manufacturer Pratt & Whitney Rocketdyne (PWR).

Click here for T&R Articles: http://www.nasaspaceflight.com/tag/T&R/

“Directed by SSP to prepare an integrated approach for an alternative to using flight Space Shuttle Main Engines (SSMEs) on post SSP orbiter displays. To obtain authorization and funding to design, build, deliver, and install nine (9) Replica Shuttle Main Engines (RSMEs) to replace flight SSMEs on orbiters,” noted the presentation.

“To preserve the SSME flight engines for future use, NASA MSFC (Marshall Space Flight Center) / KSC (Kennedy Space Center) / JSC (Johnson Space Center) recommends a replica engine be provided utilizing existing inoperable nozzle assets and an adapter to simulate the SSME for display purposes.”

With the Shuttle Derived (SD) Heavy Lift Launch Vehicle (HLV) utilizing four RS-25 engines on its core stage, the available stock of SSMEs (RS-25Ds) – now located at the Stennis Space Center (SSC) – will be used during the testing and the initial launches of the SLS, prior to the switch to the expendable RS-25E version of the engine in the 2020s.

With the legacy of Shuttle living on with the HLV, Atlantis will be able to feel the rumble of the SLS launching from Pad 39B, from her new home that is already under construction at the Visitor Center.

To read about the orbiters -  from birth, processing, every single mission, through to retirement, click here for the links:
http://forum.nasaspaceflight.com/index.php?topic=25837.0

(Images: Via L2, NASA, and Boeing.)

(L2 and NSF are continuing to follow the orbiters through to their final resting places. To join L2, click here: http://www.nasaspaceflight.com/l2/)

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SSMEs Shipping Out:

The change of home from the Kennedy Space Center (KSC) to NASA’s Stennis Space Center (SSC) in south Mississippi is a natural transition for the 15 engines, not least because the SSMEs underwent testing at Stennis ahead of their flight roles with the orbiters.

However, it’s their future role of becoming part of the SLS test program which has breathed new life into the famous engines, some of which will actually gain the honor of going out in style, launching one last time with the SLS during the first few missions.

Their transition from KSC will take place one engine at a time, as they travel to Mississippi by truck. Once at SSC, the SSMEs will join SLS’ Upper Stage J-2X engine – which is being tested at the facility – allowing for all SLS engine assets to be in one location, leveraging the existing knowledge base, skills, infrastructure and personnel.

“The relocation of RS-25D engine assets represents a significant cost savings to the SLS Program by consolidating SLS engine assembly and test operations at a single facility,” said William Gerstenmaier, NASA’s associate administrator for Human Exploration and Operations Mission Directorate.

The relocation also frees up the Space Shuttle Main Engine Processing Facility at KSC, which became part of a commercial deal with Boeing – in collaboration with NASA and Space Florida – to being exclusively occupied  by the company, along with Orbiter Processing Facility 3 (OPF-3) and the Processing Control Center, as they ramp up operations for their CST-100 spacecraft.

“This enables the sharing of personnel, resources and practices across all engine projects, allows flexibility and responsiveness to the SLS program, and it is more affordable,” said Johnny Heflin, RS-25D core stage engine lead in the SLS Liquid Engines Office at Marshall.

“It also frees up the space, allowing Kennedy to move forward relative to commercial customers.”

SSME: End Of A Shuttle Era:

The RS-25s have an amazing flight record with the Space Shuttle – with only one engine suffering a problem during the entire 30 years of the program.

*To read about all three orbiters - from birth, processing, every single mission, through to retirement - click here for the links:
http://forum.nasaspaceflight.com/index.php?topic=25837.0*

That single issue occurred during STS-51F with Challenger, when one of two high pressure fuel turbopump turbine discharge temperature sensors for SSME-1 failed, leaving only one sensor active on the engine. Two minutes 12 seconds later, at Mission Elapsed Time 5mins 43secs, the second sensor failed, triggering the immediate shutdown of SSME-1.

The shutdown of SSME-1 significantly lowered the thrust profile for Challenger and triggered the only in-flight abort in Shuttle Program history: an Abort To Orbit (ATO) which allowed Challenger and her seven-member crew to reach a lower-than-planned but safe and stable orbit.

Nonetheless, before Challenger could complete her prolonged ascent (nearly 9mins 45secs in duration due to the lost thrust from SSME-1), an identical high pressure turbopump temperature sensor failure occurred in SSME-2.

Booster Systems Engineer Jenny M. Howard in Mission Control Houston acted immediately, instructing the crew to inhibit any further automatic SSME shutdowns based on readings from the remaining sensors. This quick action prevented the loss of another engine and a possible abort scenario far more risky or far worse than the already in-progress ATO.

When Challenger finally reached orbit, several aspects of the mission were retooled to account for the lower-than-planned orbital altitude.

Click here to read recent articles on the SSMEs: http://www.nasaspaceflight.com/tag/ssme/

As per the In Flight Anomaly (IFA) reports for the final three missions, all nine of the SSMEs performed admirably, as they assisted the orbiters for the ride uphill into orbit.

For STS-133, all three of Discovery’s SSMEs last flew with Atlantis during STS-129, although in different positions – after they required removing and re-installing in different positions, in order to allow a changeout of ME-1′s Low Pressure Oxidizer Turbo Pump (LPOTP) early in the flow.

Discovery flew with Main Engine 1 (ME-1) – serial number 2044, ME-2 – 2048 and ME-3 – 2058. All their related hardware was the same as that which flew with Atlantis, bar a couple of elements, such as a new nozzle for ME-1.

The only notable issue with the SSMEs occurred pre-launch, relating to a power issue with the redundant Main Engine Controller (MEC) on SSME 3.

The SSME controllers provides complete and continuous monitoring and control of engine operation. In addition, it performs maintenance and start preparation checks, and collects data for historical and maintenance purposes.

STS-133 Specific – Including ET Stringer Issue – Articles: http://www.nasaspaceflight.com/tag/sts-133/

The controller is an electronic package that contains five major sections; power supply section, input electronics section, output electronics sections, computer interface section, and digital computer unit.

Pressure, temperature, pump speed, flowrate, and position sensors supply the input signals. Output signals operate spark igniters, solenoid valves, and hydraulic actuators. The controller is dual redundant, which gives it normal, fail-operate, and fail-safe operational mode capability. The problem was specific to the redundant controller on ME-3.

Actions taken during troubleshooting included the installation of a breakout box and the testing of three single phase circuit breakers for SSMEC 3B on Panel L4. Although this inspection was limited by access, engineers pro-actively replaced all 18 SSMEC circuit breakers at the recommendation of management.

The problem soon became clear when CB 109 was inspected, with a clear observation of non-conductive debris on the hardware, a key candidate for the original problem seen with SSME 3′s redundant MEC.

After the troubleshooting was signed off at the Flight Readiness Review (FRR), all three engines – and controllers – performed without issue during ascent.

“Engine operation was nominal. ME-1 2044, ME-2 2048, ME-3 2058 – No SSME IFA Identified,” noted the STS-133 SSME IFA presentation (L2 Link to Presentation). “SSME observations are encompassed by previous flight and/or test experience and identified as no impact.

For STS-134, Endeavour’s ride into orbit was aided by a noisy trio that were no stranger to the aft of the youngest orbiter in the fleet, after pushing her uphill during STS-130.

The engines were installed for one final trip with Endeavour in the following positions on the orbiter: ME-1 – 2059, ME-2 – 2061, while 2057 was ME-3.

Only one item of interest made it into the FRR documentation for the SSMEs ahead of STS-134′s mission, referencing the incident when an ELSA (Life Support) bottle fell from the entrance level near the 50-2 door and hit Main Engine 2 (ME-2) during Vehicle Assembly Building (VAB) processing operations.

“STS-134 Endeavour ME 2 ELSA Bottle Damage Inspections: Issue: Possible handling damage to ME-2. Background: ELSA Bottle dropped from above ME-2 to heat shield adjacent to controller during VAB processing. Damage observed above and adjacent to engine,” noted the STS-134 SSME SSP FRR presentation (L2 Link to Presentation).

“Dent in Orbiter GN2 Line. Dent on edge of Heat Shield near ME-2 controller. Witness statements and damage indicate no engine impact. Assessment conducted around 4.5 Ft assuming possible engine contact.”

With this issue cleared, Endeavour launched on her final mission without incident and successfully completed her mission on June 1, 2011.

As what became a regular observation, the 14-15 IFA presentations per mission (all acquired by L2 –  link to presentation collection) reviewing the mission post flight included a very short SSME presentation, noting no anomalies (L2 Link to Presentation).

STS-134 Specific Articles: http://www.nasaspaceflight.com/tag/sts-134/

For STS-135, Atlantis’ engines were ME-1 – 2047, ME-2 – 2060 and ME-3 – 2045.

Again, the only incident of note came before the engines were fired up at launch, when IPR-49 (Interim Problem Report) noted a problem with the Main Fuel Valve (MFV) on SSME-3, spotted during a tanking test to check the integrity of the modified stringers on the stack’s External Tank (ET-138).

The MFV is a ball valve with a 2.5-inch tubular flow passage and is flange-mounted between the high pressure fuel duct and nozzle diffuser. The valve controls the flow of fuel from the HPFTP (High Pressure Fuel Turbopump) to the coolant circuits and preburners.

The issue – the observation of a leak – was also covered in depth via the STS-135 SSP Flight Readiness Review (FRR) presentation for the SSMEs (L2 Link to Presentation), which covered how the issue was spotted during the Tanking Test, as it breached the Launch Commit Criteria (LCC) limitations.

As a result, the issue would have scrubbed the launch day countdown, showing a bonus side-effect of finding the problem during the Tanking Test.

“Issue: STS-135, ME-3 (2045) Main Fuel Valve (MFV) skin temperatures indicated a MFV leak during the early stages of STS-135 tanking test. Temps violated minimum limit (LCC SSME-02). Tanking test continued with engines isolated from the fuel supply,” noted the FRR presentation.

The reference to the skin temperatures related to sensors mounted to the outside wall of the downstream duct of the MFV to detect leakage during chill. Low temperatures are indicative of a MFV leak. The LCC limits are based on the vast flight experience of the Shuttle Program.

The MFV was replaced out at the pad and put through a series of leak checks. While those passed, the real test came during launch day, when the system was put through the cryogenic environment of tanking. Again, the skilled KSC and SSME engineers were shown to have successfully fixed the problem, as Atlantis launched for the final time without issue.

STS-135 Specific Articles: http://www.nasaspaceflight.com/tag/sts-135/

Now these stalwart engines – which includes the spare flight set: ME-1 – 2052 ME-2 – 2051 and ME-3 – 2054 – plus three others, are departing KSC once again – this time by road.

SSME To SLS Core:

Their potential role with the SLS was noted during the final flights of the Shuttle, as the 2010 Authorization Act reversed the FY2011 budget proposal which would not have seen any involvement of the RS-25s.

With a Shuttle Derived (SD) version of the Heavy Lift Launch Vehicle (HLV) consistently winning during trade studies, which once again pointed at a configuration which used RS-25s as the preference, the Program Requirements Control Board (PRCB) took action to protect the engines.

While NASA’s “White House-aligned” leadership continued to avoid pressing forward with the confirmation of the SD HLV SLS configuration, the PRCB stepped in to “preserve the SSME flight engines for future Agency use” (L2 Link to Presentation)- adding to a previous action to slow down the Transition and Retirement (T&R) of the contractor ability to manufacture flight spares for the RS-25s.

The PRCB also provided the approval for the orbiters to gain Replica Shuttle Main Engines (RSMEs) – previously scrapped nozzles installed via an adaptor – for when the vehicles retire to exhibitions, freeing up the flight flown SSMEs.

For SLS/HLV Articles, click here: http://www.nasaspaceflight.com/tag/hlv/

With the orbiters also donating large elements of their Main Propulsion System (MPS) – a heavily related collection of plumbing and lines – to the SLS program, a large amount of the HLV’s core guts will be from the orbiters for at least the testing/pathfinder stage, through to the opening launches.

The ongoing trades taking place at the Marshall Space Flight Center (MSFC) are also working through the core’s configuration for the three versions of the SLS, namely the Block I – 70mt, the Block IA – 100mt, and the Block II – 130mt vehicles.

Technically, SLS could launch with three, four or five RS-25s from the outset. However, with three engines on the core, and the automatic need for the core to be “stretched” – based on the five segment boosters on the configuration – using four engines would allow the vehicle to fly fully fueled in all configurations, saving the extra calculations/testing for an under-filled three engine core.

Per the meetings – as much as no decision has been made at this time ahead of the key Systems Requirements Review (SRR) and Systems Design Review (SDR) – it appears four engines on the first stage would be best prescribed for the SLS from the start, per sources.

SLS will naturally evolve after the opening flights of the Block I SLS, with SSME contractor Pratt & Whitney Rocketdyne (PWR) producing RS-25E engines for the rest of the SLS’ lifetime. The RS-25E – based on the reusable SSME (RS-25D) – is expendable and thus requires less long-life hardware items, in turn making it cheaper to produce.
—–
Please note: Clickable links with (L2) references point directly to cited L2 content. Such content is only available to L2 members (please ensure you are logged in). All other clickable links point to NSF articles and open content.

Images: Via L2 content, driven by L2′s fast exapanding SLS specific L2 section, which includes, presentations, videos, graphics and internal updates on the SLS and HLV, available on no other site. Other images via NASA.)

(L2 is – as it has been for the past several years – providing full, exclusive SLS coverage, available no where else on the internet. To join L2, click here: http://www.nasaspaceflight.com/l2/)

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Discovery’s Final Months At KSC:

The veteran orbiter marked the beginning of the end for the orbiter’s role of conducting missions under the NASA call sign, when she returned from the highly successful STS-133 mission. Soon after, Discovery was placed into the Transition and Retirement (T&R) flow, which was always going to result in her being the first orbiter to leave the Kennedy Space Center (KSC) for one final time.

For that final trip, Discovery will be rolled to the Shuttle Landing Facility (SLF), hoisted up by the Mate/Demate Device (MDD), prior to being mated atop of the awaiting Shuttle Carrier Aircraft (SCA), which will fly Discovery to the Smithsonian’s National Air and Space Museum near Washington, D.C.

In fact, Discovery’s T&R flow schedule shows she will be coming to the end of preparations for the trip by the holiday break in late-December 2011,  Those schedules – which are subject to change – show that by January 3, 2012, Discovery will be “ready for ferry”.

Soon after, Discovery will be rolled out of her Orbiter Processing Facility (OPF-1) and into Vehicle Assembly Building (VAB) High Bay 4 (HB4) for storage. She will remain in storage until April 10, when she will be towed to the SLF and hoisted atop the SCA.

The non-official date – based on preliminary internal information – has Discovery departing KSC on April 12, 2012, just as her older sister Columbia did 31 years previously, during the very first Space Shuttle launch.

Discovery’s point of arrival, Dulles Airport, currently believe Discovery is due to arrive around April 16, as much as they do not have a confirmed date. The Smithsonian’s current orbiter, Enterprise, will be moved to a staging point just days ahead of Discovery’s arrival.

This means it may be possible that Discovery and Enterprise will be parked together on the tarmac at Udvar-Hazy for a short period of time for photos and video right after Discovery is wheels-down.

Discovery will be removed from the back of the SCA via cranes and lowered onto the ground at Dulles, a process which has already been practised at KSC’s SLF earlier in the year.

Shortly thereafter, Enterprise will be hoisted on top of the SCA in preparation for her ferry flight to JFK International Airport in New York.

Discovery will still sport her battle scars of re-entry on her Thermal Protection System (TPS) blankets. However, she will be missing some of the hardware she used during her operational life.

To her visitors, she will have a very similar appearance on the surface, but her Orbital Manuevering System (OMS) Pods and Forward Reaction Control System (FRCS) were near-gutted during safing operations at the White Sands facility in New Mexico.

She will also be sporting three RSMEs, as opposed to SSMEs, following the Program Requirements Control Board (PRCB) decision to protect all flight-able SSMEs for the SLS program.

The PRCB Change Request presentation (available on L2) noted direction from the Space Shuttle Program (SSP) to roadmap the ability to keep the engines, and replace them with replicas for when the retired vehicles go on display at their exhibitions.

“Directed by SSP to prepare an integrated approach for an alternative to using flight Space Shuttle Main Engines (SSMEs) on post SSP orbiter displays. To obtain authorization and funding to design, build, deliver, and install nine (9) Replica Shuttle Main Engines (RSMEs) to replace flight SSMEs on orbiters,” noted the presentation.

“To preserve the SSME flight engines for future use, NASA MSFC (Marshall Space Flight Center) / KSC (Kennedy Space Center) / JSC (Johnson Space Center) recommends a replica engine be provided utilizing existing inoperable nozzle assets and an adapter to simulate the SSME for display purposes.”

With the Shuttle Derived (SD) Heavy Lift Launch Vehicle (HLV) utilizing between three and five RS-25 engines on its core stage, the available stock of SSMEs (RS-25Ds) – comprising of three sets from each orbiter, a spare set of three and up to three others located outside of KSC – will be used during the testing and initial launches of the SLS, prior to the switch to the expendable RS-25E version of the engine in the 2020s.

For the orbiters going on display, SSME contractor Pratt & Whitney Rocketdyne (PWR) developed the RSME, of which nine have been fabricated for installation on the vehicles.

While a flight ready SSME consists of large amounts of plumbing, turbopumps and electronics, etc. The RSMEs simply consist of a scrap – but cosmetically repaired – nozzle, with an adaptor to install it into the aft of the retired orbiter.

The internal schedules showed the installation of the RSMEs was scheduled to take place in October, meaning they are behind on the timeline with this week’s completion of the task. However, there is a large amount of flexibility in the flow, given the aforementioned information that Discovery’s schedule allowed for four months between her “ready to ferry” date and her eventual departure from Florida.

With all three RSMEs now installed on Discovery, she is starting to return from her rather sorry looking appearance of a vehicle with no engines, no OMS Pods and no FRCS. This process was required to allow for the complete safing of the vehicle, due to the amount of hazardous substances her powered systems contained after returning from STS-133.

Click here for other T&R Articles: http://www.nasaspaceflight.com/tag/t&r/

The T&R plans for Atlantis and Endeavour are currently under embargo, while the Johnson Space Center (JSC) – which missed out on a flown orbiter, are soon to expect delivery of the high-fidelity model which is being dismantled from its current home at the KSC Visitor Complex.

The model is scheduled to be moved to the Turn Basin at 7am (first motion) on Sunday, December 11, with the move requiring removal of light poles and other obstructions – work which will begin on December 9.

The replica External Tank and Solid Rocket Boosters (SRBs) which sat next to the orbiter at the display have also been dismantled and will be placed into temporary storage at KSC.

Ground breaking on a new exhibition facility – which is going to be the eventual home for Atlantis – is expected to start early in the new year.

(Images: Via L2 content and NASA.)

(L2 and NSF are continuing to follow the orbiters through their transitional period. To join L2, click here: http://www.nasaspaceflight.com/l2/)

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SLS Configurations:

The ongoing trades taking place at the Marshall Space Flight Center (MSFC) are a notable change from the Constellation Program (CxP) issue of making major configuration decisions years down the line, which – in the case of Ares – was well-known as one of the contributing factors to causing impacts to the entire vehicle.

Technically, SLS could launch with three, four or five RS-25s from the outset. However, with three engines on the core, and the automatic need for the core to be “stretched” – based on the five segment boosters on the configuration – using four engines will allow the vehicle to fly fully fueled in all configurations saving the extra calculations/testing for an under-filled three engine core.

As such, it appears managers have already decided that using four engines on the first stage would be best prescribed for the SLS from the start.

Revealing details of the core stage discussions, a “face-to-face” outbrief in late September resulted in a highly detailed presentation (acquired by L2). The meeting involved SLS operations personnel and Mission Operations Directorate (MOD) departments.

In the presentation’s SLS Overview, the Launch Vehicle Blocks are shown in three configurations, namely Block I, Block IA and Block II – the latter of which is the fully evolved 130mt launch vehicle.

The Block I vehicle has two missions, opening with the flight to send an uncrewed Orion (MPCV) on a Circumlunar trip around the moon, followed by a crewed lunar orbit mission. While schedules are still being worked, managers are aiming to launch SLS-1 in 2017, followed by SLS-2 in 2019.

Block I uses a Core Stage Propulsion of LO2/LH2 with Four SSMEs (RS-25Ds) now sported by the configuration, an advance on the three RS-25Ds, as previously noted. Core Stage Tank design (structure, MPS (Main Propulsion System), avionics) will be used for all subsequent SLS flights. Tanks, MPS, and Engine interfaces will be sized for 130 mt vehicle.

Engineers are also in the final stages of completing the list of hardware that will be removed from the aft of the retired orbiters, ahead of being donated to the SLS test program and flight hardware.

As already well-known, these two Block I flights use the Ares Five-Segment configuration. These Solid Rocket Boosters (SRBs) will not be recovered from the Atlantic.

Also confirmed by the presentation, after first revealed by this site, the On-Orbit Stage will utilize the existing Delta-IV Upper Stage Interim Cryogenic Propulsion Stage (iCPS), driven by LO2/LH2. Also known as the kick-stage, this is a temporary measure ahead of SLS’ purpose built hardware.

“iCPS (Delta IV) will be used for two flights: Originally planned to be used with no s/w (software) mods. Current thinking is that s/w mods will be required. Requires Delta IV flight computer redesign. Will include the following four commands: Authority to Proceed. Engine Shutdown. Upload Burn Targets. State Vector Update,” added the presentation.

“Provides orbit insertion and trans-lunar injection burn. SLS will purchase two Delta-IV Upper Stages to enable Block 1 flights early. Will likely require Delta IV avionics redesign to meet mission risk constraints.”

Block IA will then take over, providing the mission configuration for the bulk of the 2020s, from SLS-1 to around SLS-13. This configuration will have the same appearance as the Block I, bar the Cargo version, which will debut after the Lunar missions.

The core will again utilize RS-25s, although it will first use up the stock of SSMEs (RS-25Ds), of which the presentation notes there are currently 14-15* in total. This figure includes the three sets of three donated by each of the Shuttle orbiters, and a spare set of three which were already held at the Kennedy Space Center (KSC) in the event of a pad changeout.

*Note, other L2 documentation state the number is 15 engines, plus two development engines, and an additional spare Line Replacement Unit (LRU).

Due to the core’s engine configuration, an advance on the four engines can be made – moving to the full utilization of five RS-25s on the core – as is noted by the overview of the Block IA, which acknowledges this version of the SLS will be when the program eventually moves on to the cheaper, expendable RS-25Es.

“Core Stage Propulsion Four-five expendable RS-25E. Develop expendable, cheaper version of SSME for on-ramp when the existing Shuttle inventory is used up (~14-15* full SSME’s),” noted the presentation, overviewing what will be a 100mt capable launch vehicle.

Most of that additional power will come via the debut of the new “advanced” boosters, which will be decided via a “competitive procurement”, resulting in either ATK winning through with a more powerful version of their Solids, or a switch to a liquid booster, likely to powered by RP-1 (Kerosene).

(Image taken from the amazing 220mb DM-2 Five Seg Motor Ground Test Video – available in L2).

“Advanced Booster: Composite SRBs or RP-based Liquid Boosters. Begin competitive procurement for SRB replacement. The trade space can include composite-case SRB’s or kerosene-based liquid boosters.”

With the Delta IV kick stage no longer required, the Block IA will be prepared to host the “Large On-Orbit Stage”, a new Cryo Prop Stage (CPS) driven by LO2/LH2, pointing to some flexibility of missions prior to the fully evolved SLS being ready.

For SLS/HLV Articles, click here: http://www.nasaspaceflight.com/tag/hlv/

“NASA designed on-orbit stage. Not part of SLS vehicle. Paid for by SLS Program. Enables Exploration missions,” added the presentation, which may be pointing more towards it being too early to know when the CPS will be used. “Utilizes Avionics independent from SLS.

“CPS (NASA) will be a new design: Will be used for Block IA+. Is being designed as a separate Project within SLS. Enables Exploration missions.”

Then comes the massive 130mt, fully evolved, Block II SLS, which will be a nature advancement on the Block IA configuration, with the only difference being the size of the vehicle, as it grows by nearly 80 feet – when compared to the Block IA cargo vehicle – to find space for the new Upper Stage.

Using three J-2X’s from the Constellation Program, development of the engines and stage will continue alongside the SLS work, prior to being held back until the Block II is ready to fly.

“Complete J-2X and put “on the shelf” for later use with SLS Block II. Move Integrated Stack avionics to this stage. This Upper Stage burns out prior to orbit insertion (ala Saturn V).”

This, as NASA have been claiming for some time now, will be the flagship launch vehicle that will send humans – and their supporting hardware – to Mars.

While less technical than the presentation used in the above content, a superb 48 page industry-level overview of the SLS has also been produced (and acquired by L2), which provides some of the first real mission capability overviews and industry base benefits for the SLS. This will form the basis of the next SLS article on this site.

(Images: Via L2 content, driven by L2′s new SLS specific L2 section, which includes, presentations, videos, graphics and internal updates on the SLS and HLV, available on no other site. Other images via NASA.)

(L2 is – as it has been for the past several years – providing full exclusive SLS coverage, available no where else on the internet. To join L2, click here: http://www.nasaspaceflight.com/l2/)

Related posts:

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Shuttle to SLS MPS:

The MPS relates to the powerhouse in the aft compartment of the vehicle, aiding the acceleration from lift-off of an orbiter to Main Engine Cutoff (MECO) – the phase of ascent referred to as “powered flight”.

As such, the Integrated MPS consists of the three Space Shuttle Main Engines (SSMEs), an external propellant tank (ET), a propellant management system used to transport fuel and oxidizer from the tank to the engines, and a multipurpose helium system.

For SLS, the External Tank will be translated into the core stage, becoming part of the in-line HLV. The second stage will ride on top of the core, with the Orion (Multi-Purpose Crew Vehicle) riding on top of the second stage on the crewed version of SLS, replaced by a payload on the cargo version.

Two Solid Rocket Boosters (SRBs) will be attached to either side of the core stage, not unlike the Shuttle stack, as much as these boosters will be larger five segment motors, potentially changing to a liquid version later in SLS’ lifetime.

For SLS/HLV Articles, click here: http://www.nasaspaceflight.com/tag/hlv/

As has been noted previously, SLS will utilize SSMEs – otherwise known as RS-25s. The stock of SSME (RS-25D) engines are currently being preserved at the Kennedy Space Center (KSC), after being donated by the Space Shuttle Program (SSP). There are at least three sets of three engines, removed from each orbiter, along with a spare set of three engines (12 engines in total).

Prior to the orbiters going on display at their respective exhibition sites, each vehicle will be fitted with three Replica Shuttle Main Engines (RSMEs) – made from previously scrapped nozzles and installed via an adaptor – which are being fabricated by SSME contractor Pratt & Whitney Rocketdyne (PWR).

Given the adaptor will be installed inside the SSME domes shields, visitors to the orbiters at their exhibitions won’t notice the difference, especially as the nozzles will be real hardware, repaired from their previous scrap designation.

The recommendation to preserve the flown SSMEs for future use was called for by NASA’s MSFC (Marshall Space Flight Center), KSC and JSC (Johnson Space Center), providing free engines for SLS to utilize on its opening flights.

All of the reusable engines will be destroyed when the unrecoverable core stage burns up in the designated disposal corridor, not unlike the shuttle ET.

As seen in the latest SLS documentation, the plan is to move to a cheaper, non-reusable version of the SSME – known as the RS-25E – once the RS-25D stock is exhausted by the SLS flights.

Now SLS managers have requested the use of the major plumbing inside the orbiter’s own MPS system, which is a natural match for the RS-25s.

“There has been a request to removed the entire MPS (Main Propulsion System) from the orbiters for SLS (Space Launch System),” noted KSC processing information (L2), adding such an operation would delay the shipping dates of the orbiters by over half a year.

“This would be six to nine month impact to the T&R (Transition and Retirement) schedule (for the orbiters).”

This effectively relates to the guts of the orbiters, specifically known as the Orbiter MPS.

The Orbiter MPS includes major hardware items such as the Propellant Management System (PMS).

The MPS PMS consists of manifolds, distribution lines, and valves that transport propellants from the tanks to the three main engines for combustion, and gases from the engines to the tank for pressurization.

The PMS is the lifeline of the integrated MPS. In addition to its primary function of feeding propellants from the External Tank to the engines during powered flight, the PMS also controls the loading of propellants before launch, the post-MECO propellant dump and vacuum inerting.

The removal of this hardware inside the aft compartments of the orbiters would involve disconnecting major hardware – such as the Propellant Feedline Manifolds, which consists of 17-inch and 12-inch piping – through the three spaces left vacant by the removed SSMEs.

Items which would be removed includes the feedlines – vacuum jacketed for H2, insulated for O2 – Fill and Drain (F&D) lines, recirculation lines (H2), and gaseous H2 and O2 lines – which are used to maintain pressure in the ET – via more well known items of hardware such as the Flow Control Valves (FCVs).

The FCVs were highlighted during an investigation into a small liberation from one of the valve’s poppet’s during STS-126.

Mitigation procedures – which included screening of flown valves post-flight at the frabricator Vacco - resulted in no further issues.

Click here for NASASpaceflight.com articles on the FCV issue since STS-126

These are all natural elements of hardware which would provide both the SLS core and the SLS engines with the role they had previously enjoyed with the orbiter, such as the FCV-related Ullage Pressure System (UPS) – which deals with the volume in the LH2 and LO2 tanks not occupied by liquid propellant.

The ullage pressure system consists of the sensors, lines, and valves that are used to collect gaseous propellants (gaseous hydrogen and gaseous oxygen) from the three main engines; the system supplies the gaseous propellants to the External Tank to maintain propellant tank pressure during engine operation, as well as maintaining tank structural integrity.

Propellants must be supplied to the SSME with adequate head pressure for proper engine operation.

Also to be removed would be the MPS helium system, which consists of storage tanks, distribution lines, regulators, and valves that supply helium to the main engines and the MPS PMS.

The helium supply tanks consist of three large (17.3-cubic-foot) and seven small (4.7-cubic-foot) helium tanks known as Composite Overwrap Pressure Vessels (COPV). Each large tank is plumbed to two of the small tanks to form three clusters. Each cluster provides helium to one of the main engines. The remaining small tank is the pneumatic helium supply.

Although this would all result in a large amount of hardware being removed from the aft of the orbiters, visitors to the exhibitions would not have been able to see – or likely have any access – to the aft compartment, meaning their visual appearance will not be altered.

A final decision on proceeding with this work is expected later this year.

(Images: Via Larry Sullivan, Chris Gebhardt (MaxQ Entertainment/NASASpaceflight.com) orbiter engineering tour video (1000mb) available on L2, plus L2 content - driven by L2′s new SLS specific L2 section, which includes, presentations, videos, graphics and internal updates on the SLS and HLV available no where else on the internet).

(L2 is – as it has been for the past several years – providing full exclusive future vehicle coverage, available no where else on the internet. To join L2, click here: http://www.nasaspaceflight.com/l2/)

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The Ongoing SLS Delay:

As admitted by NASA Administrator Charlie Bolden, the decision on the configuration of the Space Launch System (SLS) was made on June 15, a decision based on the winning Design Reference Vehicle (DRM) out of the Marshall Space Flight Center (MSFC) hosted RAC (Requirements Analysis Cycle) study effort.

Memos on the decision, based around the utilization of a Shuttle Derived (SD) Heavy Lift Launch Vehicle (HLV) – as requested in the Authorization Act – soon circulated at the main NASA centers, with references to an official announcement to be made on July 8, the launch date for STS-135.

In a sign of how widespread the information was, Atlantis’ commander Chris Ferguson told the media to expect the announcement on the next vehicle to be made on launch day, following his arrival at the Shuttle Landing Facility (SLF) from Houston. His statement wasn’t retracted, nor was it corrected, by NASA Public Affairs.

July 8 came and went, as Atlantis launched on the final NASA shuttle mission – and most likely the last domestic manned mission for several years.

General Bolden was then called in front of a “Full Committee Hearing – A Review of NASA’s Space Launch System“, where lawmakers were given the chance to ask questions about the delay in pressing on with the SLS.

After a tough opening question, the General gave arguably his most impressive public performance to date, holding firm on why he was not able to reveal specifics on the vehicle’s configuration. His defence was related to industry restrictions and an ongoing independent cost analysis effort by Booz Allen.

That costing effort – which began on July 5 – is likely to be completed by mid-August, while an announcement on the configuration of the vehicle, is expected “soon”.

 An attempt to request NASA push on with making a public statement on the SLS configuration to the media – to coincide with Atlantis’ landing at the Kennedy Space Center – was turned down by NASA’s leadership.

The continued delays to the announcement are now causing numerous managers and workers – at least those remaining after the massive jobs losses shortly after Atlantis’ return – to question if the delay is based on politically-aligned tactics to kill the SLS.

As many are aware, a second round of job cuts are expected to be carried out soon at key SLS bases – such as the Michoud Assembly Facility (MAF) in New Orleans, where managers have attempted to delay and extend WARN notices in the hope of bridging the gap between Shuttle and SLS – again based on the raised hopes of the June configuration decision by General Bolden.

The continued delays have now resulted in MAF’s management losing patience, as August 26 was set as the date for all of the remaining workforce – a key SLS skill set – to be released.

In effect, those opposed to SLS – such as the architects of the FY2011 plan – only need to delay another month before they can cite the “difficulties and costs” of having to rehire workers to build a vehicle which could have been announced when the workforce was still in place.

SLS Configuration and Schedule:

The SLS configuration is – as expected -  based around a SD HLV, using “Shuttle” boosters, engines and external tank heritage. However, information – acquired in the new L2 SLS section – has provided the most recent and comprehensive overview on the specifics of what is a core vehicle from the onset.

Click here for recent SLS Articles:
http://www.nasaspaceflight.com/tag/hlv/

Initially, the call was to debut the SLS in 2016. As recently noted, the schedule for the opening flight has moved to December 2017 – although it now has an actual mission.

The mission will be lunar, with SLS-1 lofting Orion (MPCV) on an unmanned mission around the Moon.

Ironically, SpaceX recently noted – during their Falcon Heavy announcement – they are close to such a mission capability, far sooner than 2017.

SLS-1 will debut the vehicle in a 2.5 configuration, utilizing three Space Shuttle Main Engines (SSMEs) – otherwise known as RS-25Ds, donated by the Shuttle fleet – on an 8.4m diameter “External Tank” core, stretching 212 feet in length, with five segment Solid Rocket Boosters (SRBs).

It will also sport a 5m “kick stage” – which sources claim is a man rated version of the Boeing Delta IV upper stage. This stage was also listed as one of the candidates for the Sidemount SD HLV.

Nearly four years will pass before the next SLS launch in August 2021, known as SLS-2, a vehicle which is identical to SLS-1, with the only difference being an element of the mission, which would be a manned trip around the moon in the MPCV, prior to a west coast landing in the Pacific.

Although the manifest is very much “to be decided” – August, 2022 would be the next launch date, with SLS-3 again using the same configuration, as would SLS-4 one year later.

SLS-5, in August 2024, would be the debut of the Cargo SLS, with a new fairing and a vehicle hardware change possible – as the winner of the booster competition would debut with this HLV.

While ATK’s Reusable Solid Rocket Motor (RSRM) boosters may continue, should they win the competition, sources claim a likely switch to an RP-1/LOX booster – although an actual engine for such a booster has not been cited at this time.

Sources note the potential options for the liquid booster engine range from a TR-107, to a cluster of AJ-26-500s, to maybe even SpaceX’s Merlin 2. Based on such a manifest becoming a reality, such options would have well over a decade to provide such an option for the SLS.

SLS-6 – August 2025 – would return to the manned configuration, although no mission other than “exploration” – possibly as part of a Near Earth Object (NEO) mission – has been cited by the information.

SLS-7 – August 2026 – a Cargo SLS launch, would see one change to the vehicle, as the expendable SSME – known as the RS-25E – would be employed on the vehicle, taken over from the exhausted Shuttle SSME stock. Again, three engines would be required, as much as all of the SLS vehicles will be designed to have “space” for five engines.

With the manned and cargo SLS’ taking it in turns for the single mission per year role, SLS-11 – August, 2030 – would be the next change, as the five engine core is filled with the two extra RS-25Es, utilizing the full core power plant.

This configuration’s debut would be a cargo based mission, followed by a crewed mission one year later.

And then, in August of 2032, the evolved SLS is expected to debut (see image left), again based on the same 5xRS-25E driven core, but this time with a full Upper Stage, becoming the 130mt+ HLV. This debut (SLS-13) would be – as expected – based around a cargo mission.

Sources note the Upper Stage for the evolved SLS would utilize three J-2Xs, an engine which was originally set be involved with the since-cancelled Ares vehicles.

Other notes of interest claim the Ares Mobile Launcher (ML) has earned a reprieve, after it was initially claimed it would be cheaper to build a new launch platform, as opposed to carrying out expensive changes to the Fixed Service Structure (FSS) and Launch Mount – both of which were very specifically designed with the Ares I in mind.

The Ares ML – currently parked near the Vehicle Assembly Building (VAB) – was also going to be hooked up to the Roller Coaster Emergency Egress System (ESS), a massive structure which was to be built in-situ at Pad 39B. However, it is understood that despite a large amount of money being spent on the design phase, this concept has been scrapped and won’t return for the SLS.

Other efforts, such as the modifications and long-term life extension of at least one of the Crawler Transporters (CTs) to provide the ride for the SLS to the pad, are continuing.

As noted at the start of the article, sources have noted this schedule is preliminary, based on a poor funding forecast – a “worst case scenario” manifest, although no one was able to provide even a draft version of an improved schedule.

(Images: Via L2 content, driven by L2′s new SLS specific L2 section, which includes, presentations, videos, graphics and internal updates on the SLS and HLV.

(L2 is – as it has been for the past several years – providing full exclusive future vehicle coverage, available no where else on the internet. To join L2, click here: http://www.nasaspaceflight.com/l2/)

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