Marshall Space Flight Center’s Danny Davis, manager of the Upper Stage of the new Ares I Crew Launch Vehicle (CLV) insisted that the vehicle is making good progress through its early design phases.
Davis – in the second of a three part interview with NASASpaceflight.com – dismissed documented concerns about weight issues, and elaborated on progress made with the CLV, including the Upper Stage’s J-2X engine.
Part 2 of a 3 part series interview between NASASpaceflight.com’s Ross B Tierney and MSFC Ares I Upper Stage Manager David Davis.
**Click here for Part 1** **Ares I Forum**
Interview Part 2:
NASASpaceflight.com: You attended the recent Technical Interchange Meeting [TIM] at KSC. Can you explain what it involved, and what feedback did it produce with regard to the Ares in general, and especially to your team?
Davis: The TIM at KSC was an opportunity for the design team at MSFC and GRC to discuss mutual design issues such as umbilical design options and requirements with the KSC design team. Our teams meet via telecom several times each week, but the face to face meetings are necessary to facilitate more detailed dialog. The teams worked through umbilical requirements for fluid transfer, electrical connection, and roles and responsibilities for commanding and timing of the launch sequence. The design team left with a better understanding of the sequences needed for launch processing.
NASASpaceflight.com: This site has learned that a NASA study indicated that the U/S is about 7,000lb ‘overweight’ compared to its DAC-0 mass allocation of 26,445lb. This was indicated to be a ‘showstopper’ to the entire Ares-I development program, so caused quite a stir amongst our readers. They are very eager to understand this issue in detail, so can you explain what actually happened?
Davis: We do not believe the stage to be ‘7,000lb ‘overweight” – we believe we will meet our performance targets. We have validated engineering tools that are used to set the allocations to the elements for initial planning. These tools are anchored in historical ‘as flown’ capabilities and, if anything, tend to ‘envelope’ loads and weights. We are in the process of building our more detailed, bottoms up models estimates and are synching with these allocations – working through various trade studies to get the most operable design that meets the cost, schedule and performance requirements.
Caution: it can be misleading to take any arbitrary ‘snapshot’ in time as there are numerous trades and option assessments underway – this will all come to closure after SRR in a baseline concept. In addition, we carry significant mass growth allowance for the stages and engine (upperstage, J-2X and 1st stage) which allows for typical mass evolution from concept to final design (depending on the maturity of a particular subsystem, based on history) and then on top of that carry a significant factor for overall vehicle performance margin. We have more design detail and margin at this point than on any other launch vehicle development program I have been associated with in my career.
NASASpaceflight.com: At what phase of the development program was this study done?
Davis: Again, we are in the handoff phase from validated concept engineering tools to more ‘bottoms up’ detailed engineering and design and are conducting a wide variety of trade studies – this is all part of the normal systems engineering processes any aerospace vehicle goes through in this formulation phase to validate requirements. We will have a baseline concept after SRR, upon which we will base the preliminary design of Ares I.
NASASpaceflight.com: Given the nature of this considerably higher mass figure in this early analysis, was it unexpected, or were your team always expecting the mass to be higher than the DAC-0 allocation at this stage of the development?
Davis: We are not surprised by early data fluctuations because of where we are in the design process, as we discussed in the answer to the previous question. We believe that we will meet our performance targets.
NASASpaceflight.com: Can you explain to us how your team intends to create a solution for this issue?
Davis: Again, we don’t see this as an ‘issue’ – its part of the normal formulation process. As we move from the requirements validation level of design to the preliminary design after SRR, we believe that there are proven design solutions to meet our requirements.
NASASpaceflight.com: Could you explain some of the various ‘options’ which are being considered to reduce the U/S mass to within the correct mass allocation and give us an idea of how much mass they are likely to each ‘save’ if applied?
Davis: Since the inception of Ares I, we have carried and have been assessing a wide variety of design options, including ‘common’ bulkhead, using composites for some dry structures (instrument unit, for example), more integrated thrust structure, integrated interstage/forward frustrum, etc – these can’t be assessed individually – we take an integrated systems perspective, looking at mass, cost, schedule, ‘illities and risk.
The attributes of the options depends on system parameters unique to our application such as the load generated by the trajectory, the change to the configuration, and manufacturing techniques. Our primary purpose now is to validate we can meet our requirements using a combination of options – we will then enter the design phase after SRR this Fall where we will get into the details of the final design. We are on track to validate our integrated requirements suite.
NASASpaceflight.com: Can you tell us what the current status is for the new engine?
Davis: The engine is making great progress – we have completed the preliminary requirements review and will hold a systems requirements review and system design review starting in October. We have injector testing underway at MSFC which is validating our Isp projections. We are disassembling the J-2S turbopumps from the X-33 aerospike engine (XRS-2200) – everything looks good so far. These pumps form the basis for the heart of the J-2X engine and we plan to have these and the gas generator (combination is called a powerpack) in test late next Spring/early Summer at NASA Stennis in the A-1 test stand.
NASASpaceflight.com: What is the expected performance P&W have been able to assure NASA of (274,500lb thrust, 448s vac Isp?), and do you have any idea what performance figures they are hoping to achieve (295,000lb thrust, 452s vac Isp)?
Davis: NASA engineers and project personnel have worked closely with PWR in designing the concept engine and setting the requirements. We are planning for a 294klbf engine at 448 sec Isp (minimum) / 452 sec (nominal) for the later lunar missions. This could come in the form of a 274klbf capability initially for LEO missions with a later modification for 294klbf or possibly just go directly to 294klbf – design and developmental testing will determine the final approach in the next year.
NASASpaceflight.com: When is the U/S program expecting delivery for first flight-ready J-2X’s for test flights?
Davis: 1st development J-2X rolls off the line in early 2010.
NASASpaceflight.com: And when are those test flights currently scheduled for?
Davis: That is still being worked with the Constellation program office, but as of now, no later than 2012 for the 1st full-up orbital flight.
NASASpaceflight.com: This site has learned that there is some form of TVC concern for the J-2X. Can you categorise this issue for us and explain how it was/is being mitigated?
Davis: We have not identified any issues with TVC for either the 1st or 2nd stage of the Ares I. The existing Shuttle RSRB TVC system used on 1st stage has approximately 2x the rate and 2x the gimbal capability we need (significant margin) for Ares I. The 2nd stage has just completed a series of trade studies to determine the most appropriate system for our application.
The result was that Ares I will use a hydraulic actuator system vs. an all electric Electro-mechanical actuator. The system chosen will be safer and lighter with good cost and operability characteristics. Either 2nd stage TVC System would have worked, and there was no concern. This is a good example of how we will be making decisions to optimize all subsystems as we move forward in the design process.
NASASpaceflight.com: Do you know if the J-2X development program will be borrowing from knowledge gained on other engine development programs such as your previous work on Fastrac and RS-84, or perhaps utilising development programs of the RS-68, SSME, Cobra or maybe even the new Integrated Powerhead Demonstrator?
Davis: Yes – this engine is using ‘lessons lived’ and sometimes derivative hardware from several programs. For example, the J-2X is using the turbomachinery modified from the J-2S engine which was recently demonstrated on the X-33 Aerospike; the J-2X injector, gas generator, valves and actuators and start system design are all grounded in the J-2 engine. Manufacturing and design techniques are all using SOA methods developed in the RS-68 program. In addition many members of the PWR and NASA team have worked the previous programs in key positions and several of the original J-2 personnel are present on the teams.
Some final comments from Davis:
NASA selected a Shuttle-derived launch architecture after a thorough apples-to-apples study last Summer – the Exploration Systems Architecture Study. NASA carefully weighed a wide variety of launch options for both crew and cargo – a Shuttle derived architecture was the clear winner when considering total cost, schedule and safety/reliability to achieve an exploration-capable system. NASA did not do this in a vacuum – in fact, we received inputs from industry, including studies funded by the agency, in the year prior to ESAS. The ESAS results were independently reviewed and concurred-in by experts outside the agency.
Last Winter and Spring, after a series of trade studies, NASA elected to alter the launch architecture to a 5 segment RSRM-derived 1st stage and a J-2X upperstage for Ares I and an Ares V core stage powered by an RS-68 (still boosted with a 5 segment RSRM and a J-2X earth departure stage).
This move was not driven by technical concerns, instead, the approach selected allows us to make a significant ‘downpayment’ towards Ares V with Ares I – lowering the overall integrated program risk to a 1st lunar landing:
– Where we had 2 upperstage engine developments (altitude start SSME and J-2X), we now have one (J-2X).
– Where we had 2 Shuttle RSRM-derived 1st stages (4 and 5 segment), we now have one (5 segment).
– With the 5 segment, we will use the same propellant (PBAN), same cases and joints/seals, same igniter, same nozzle hardware in a majority of components, a Shuttle developed, environmentally-friendly insulator, same aft-skirt and same TVC system as has been proven on 230 RSRM flights on Shuttle. In addition, 5 segment changes are anchored in a proof-of-concept 5 segment firing in October, 2003.
– Where we had a 2 step approach to a low cost core stage engine which would only be used by NASA (expendable SSME), we now have one with the RS-68, which fly’s today on the Delta IV.
In making these changes, we were able to reduce our planned expenditures in getting to the moon while maintaining system performance and safety/reliability projections. Such trades are a normal part of a rigorous systems engineering approach which NASA is employing in its exploration efforts – it’s interesting to note that the Saturn program went through 8 configuration changes from 1959 – 1962 resulting in the Saturn V, which took us to the moon.
While challenges exist – getting to space is hard – we have an experienced, highly motivated and dedicated team that is honored to have a part in this endeavor.
T-32 months to our 1st test flight!