The company made famous in the space flight industry for their giant Solid Rocket Boosters (SRBs) have put their hat into the ring for potentially carrying NASA astronauts to Low Earth Orbit (LEO) via their Liberty launch vehicle. Looking very much like the cancelled Ares I – Liberty will use a five segment booster with a Ariane 5 core stage as the Upper Stage.
The announcement allows ATK to return Liberty back into contention with the Commercial Crew Development (CCDev-2) winners, under a similar milestone structure ATK proposed when bidding for progression in NASA’s drive to return the US back to being able to domestically launch its own astronauts.
The agreement allows for NASA collaboration on the development of the company’s Liberty Launch System as part of the CCDev-2 activities, but without NASA funding. Their goal will be to successfully impress NASA enough to be brought back into the fold by the time the CCDev-3 awards are made in 2012.
They face stiff competition, not least from what are currently the two leading launch vehicles – the United Launch Alliance (ULA) Atlas V and SpaceX Falcon 9 – both of which have a crew vehicle to launch, whereas Liberty does not.
The unfunded Space Act Agreement (SAA) through NASA’s Commercial Crew Program will allow the agency and ATK to review and discuss Liberty system requirements; safety and certification plans; computational models of rocket stage performance; and avionics architecture designs.
The agreement outlines key milestones including an Initial System Design review, during which ATK will present to NASA officials the Liberty systems level requirements, preliminary design, and certification process development. This effort will continue through to the Spring of 2012.
“This agreement will provide the opportunity to look at the Liberty system to understand its design solution and risks, its capabilities and how it could be used to fly our NASA crew,” said Ed Mango, NASA’s Commercial Crew Program manager. The program is based at the agency’s Kennedy Space Center in Florida.
NASA will provide feedback to ATK based on its human spaceflight experience for advancing crew transportation system capabilities and the agency’s draft human certification requirements.
“With this SAA we believe NASA will benefit from gaining insight into the various systems we are developing, and we can benefit from the feedback,” said Kent Rominger, vice president, strategy and business development for ATK Aerospace.
“In the end, we hope to offer a commercial solution to NASA, the Department of Defense, and other commercial human spaceflight programs.”
Liberty Launch Vehicle – First Stage:
With the appearance of an Ares I – given it works on the same aerodynamic design principle – Liberty is powered by a single, five segment Solid Rocket Booster (SRB) on the first stage.
The large solid motor was set to power the Ares I, prior to the cancellation of Constellation – and may find a role with the Space Launch System (SLS), with two five segment boosters currently part of the Design Reference Vehicle (DRV).
This booster is the same design that was recently tested during the DM-3 test in Utah last week.
The booster which powered the only Ares test flight – Ares I-X – was not the same as Ares I or Liberty, as a four segment booster utilized in what was a successful launch, per test objectives.
During the development of Ares I, the five segment booster came across numerous challenges, the most famous of which was the phenomenon of Thrust Oscillation (TO).
Also known as “Resonant Burning” – described as vortices that shed within the solid rocket motors during combustion due to the shearing of internal flow at propellant discontinuities – the issue relates to when the frequency of thrust oscillations is coincident with the acoustic modes of the motor cavity.
When pressure oscillations drive resonant modes in the vehicle structure, these oscillations are capable of rendering the astronauts incapacitated, or worse.
This was the major concern, that crew health was at risk during the few seconds TO occurs, late in first stage flight. However, engineering work during the Ares I development created several options to mitigate TO on Ares I’s first stage reaching the crew seated in Orion, this risk has – it was claimed – been eliminated.
DM ground tests – and sets of instrumentation, aimed at gathering more detailed data on RSRM (Reusable Solid Rocket Motor) behaviour during the first stage of launch, on the final shuttle missions – have also proven TO to be less than expected.
Notably, the Liberty Upper Stage is also a different design when compared to the Ares I Upper Stage, further decoupling the potential TO effects, especially as TO was heavily related to the Ares I stack in the configuration with the Orion crew vehicle.
Should any concerns remain, the use of dampers and isolation – as seen with Ares I – could be used. TO is of no concern to SLS, given the configuration of the Heavy Lift Launch Vehicle (HLV).
Indeed, one of the key selling points for Liberty is the safety heritage of the motor from its days with the Space Shuttle, which – per Flight Readiness Review (FRR) and In Flight Anomaly (IFA) review presentations (all available on L2 for the last 15 missions) – has been extreemly impressive in recent years.
Refinements have been numerous, as engineers removed a number of potential issues, as a matter of course, as opposed to a program requirement.
One such example on the improvements to the boosters – which would live on via Liberty – can be seen with the redesign to the SRB Thrust Vector Control (TVC) Auxiliary Power Unit (APU) fuel pump, which was implemented on STS-133 and STS-134.
The redesign eliminated the highest – although extremely unlikely to occur – “critical 1” failure scenario, which held the potential of a LOV/C (Loss of Vehicle/Crew) event.
The change to the fuel pump related to a small carbon seal that could be lost/compromised during operation, allowing for two metal surfaces to contact – which would become an ignition source.
As noted in the FRR and Program Requirement Control Board (PRCB) documentation (L2), this change, along with the other numerous tweaks and improvements over the years, would have been implemented on the Ares I First Stage, and thus now find themselves adding to Liberty’s safety regime.
“We believe Liberty offers the safest, most reliable means of putting our crews on orbit,” noted Mr Rominger. “We have the capability – with 44,000 lbs to Low Earth Orbit (LEO) – to launch any of the commercial crew vehicles that are out there to date.”
Liberty Launch Vehicle – Upper Stage:
Liberty’s Upper Stage is the Core Stage (EPC) of the Ariane 5 launch vehicle used by Arianespace, which will be supplied under contract with EADS North America.
The latest generation of the Ariane 5 is based on an evolution of the Vulcain engine that powers the cryogenic core stage. This evolution, called Vulcain 2, provides an increased thrust through an overall mixture ratio and liquid oxygen mass flow increase.
The EPC stage is 5.4 m in diameter and 31 m long on the Ariane 5. It is powered by one Vulcain 2 engine that burns liquid hydrogen (LH2) and liquid oxygen (LO2) stored in two tanks separated with a common bulkhead. The LO2 tank is pressurized by gaseous helium and the LH2 one by a part of gaseous hydrogen coming from the regenerative circuit.
The Vulcain 2 engine develops 1 390 kN maximum thrust in vacuum. Its nozzle is gimballed for pitch and yaw control.
The engine is turbopump-fed and regeneratively cooled. The thrust chamber is fed by two independent turbopumps using a single gas generator. A cluster of GH2 thrusters are used for roll control.
The engine utilizes two turbo-pumps, driven by a gas generator, and sports a GHe pressurization system for the LOX tank and GH2 for LH2 tank.
Ignition of the engine is obtained by pyrotechnic igniters and occurs nine seconds before lift-off in order to check that’s it’s functioning properly, which leads to the main outstanding question on the use of this core stage on the Liberty Upper Stage, as it has yet been proven that the engine can be air-started, as would be required during its role with Liberty.
John Schumacher, vice president, Space Programs, EADS North America, noted that preliminary work has taken place on this requirement, when talking to reporters on Tuesday, but did not elaborate on when the work would be completed.
The engine has a record of 45 consecutive successful flights with the Ariane 5.
The mating of the ATK Solid Rocket First Stage with the Ariane 5 Core Stage is a great fit, for several reasons, according to Mr Rominger.
“What’s really fascinating with is how well the Upper Stage matches up with our First Stage. You would think they would have been designed to go with each other, but in fact they weren’t – yet they matched up better than if we had intentionally designed it that way.
“The other thing I’d like to emphasize is that in 2010, President Obama signed in a new space policy, which said we want to expand our international cooperation in space flight. So we’re taking what we believe is a very good relationship from the ISS with the European Space Agency and NASA and involving that legacy into the commercial world,
“So if you look at the Liberty system, NASA developed the first stage, and the upper stage was developed by ESA. Two companies are taking that and applying it commercially.”
Liberty would launch from the Kennedy Space Center (KSC), Pad 39B, again utilizing the Ares I approach of utilizing what is now a clean pad, which has left Pad 39A in its shuttle configuration.
The vehicle would re-employ the Ares Mobile Launcher (ML) – without requiring the large amount of redesign work to elements such as the umbilical points, Fixed Service Structure (FSS) and launch mount, as the ML was specifically designed for Ares I.
“We (ATK) asked to come into the Kennedy Space Center, because this is going to be the home of Liberty,” noted Mr Rominger, adding that Liberty could create around 300 jobs at the Florida spaceport. “Clearly the infrastructure, here at the Kennedy Space Center, is set up perfectly to process Liberty, to launch Liberty and (use) the people here.
“We would use the expertise that we have developed here over the last five decades. We are looking to take advantage of the great capability that is here today.”
It is not yet known if Liberty would utilize the Roller Coaster Emergency Egress System (EES), which was chosen via a trade study for Ares I and the ML, but never left the powerpoint stage due to the cancellation of the Constellation Program.
Such an EES would result in a massive structure being built out at the pad, allowing it to be joined up with the ML once the vehicle had rolled out to the pad. Crew would use carts – not unlike those used at a fairground – to be rushed down the track into an underground bunker.
With SLS also evaluating the use of the ML – likely as a secondary option – it has been noted by sources that the HLV would not employ the Roller Coaster ESS – instead using escape tubes in the event of a serious emergency at the pad for the crew or engineers.
Liberty would also benefit from the three 600 feet tall lightning protection system towers, again built for Ares I, out at Pad 39B. These towers were put through their paces during a heavy lightning storm ahead of STS-135, as seen via dramatic photographs from the towers (L2).
From an integration standpoint, the first stage would follow the same cross-country path as the Shuttle booster segments, arriving by rail, prior to being off loaded into Surge and then stacked in the Vehicle Assembly Building (VAB) – a process tested out when Ares I-X was stacked ahead of its test flight.
The Upper Stage would arrive by sea, as is normal procedure for Ariane 5 stages when they are shipped to their launch site at the European Spaceport in Kourou, French Guiana.
It is likely the Upper Stage could be barged all the way to the VAB, utilizing the canal and turn basin previously used to ship the shuttle’s External Tank (ET) from the Michoud Assembly Facility (MAF) in New Orleans.
Rollout of the stacked vehicle would also mirror Ares I, with the two Crawler Transporters (CTs) currently undergoing lifetime extensions and modifications to carry the much heavily SLS to the pad.
Such a sight wouldn’t be seen until 2015, which ATK and NASA note is Liberty’s current IOC (Initial Operating Capability) target.
Importantly, Liberty is without a crew transport to launch, as much as ATK have noted they have already had positive conversations with some of the commercial crew carriers.
Attracting a successful commercial crew partner will be key for Liberty’s forward path.
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