Ares I undergoes trade studies for nozzle redesign & expendability

by Chris Bergin

Marshall Space Flight Center’s Ares I First Stage Element Manager Alex Priskos has spoken to in an exclusive Q and A.

Priskos noted that the design effort on the Ares I First Stage is going forward, “consistent with what we would expect at this point,” while noting trade studies on a larger nozzle ratio – to increase performance, and potential expendability of the stage.

Huge amounts of VSE related insider news and presentations – THE most comprehensive place to follow Ares/Orion development – are available for download on L2. See list at the end of this article.

All of this article is based on documented L2 information. For an overview of how L2 works, **click here for sample**


**ARES V / Mars Transport Vehicle (MTV) LIVE UPDATE PAGES**

A number of the following questions are based on questions raised via L2 documentation.

1) What is the status of a study, claimed to be a design change to the nozzle ratio, on the Ares I first stage, to increase performance. Information notes a new nozzle design will be longer and larger in diameter (30 inches x 30 inches) at the exhaust plane and may require new aft skirts and ML (Mobile Launder) work?

A) We are evaluating a trade study to increase performance margin of the Ares I and V systems by using a slightly longer nozzle which uses the same aft skirt and related subsystems.

2) What is the status of the trade study to make the first stage expendable?

A) The trade study has been completed and is being reviewed by the Constellation Program. We will not release any information about the results until these briefings have been completed.

3) If, hypothetically, the first stage was made to be expendable, how many flights could be made with the number of casings on-hand (that is, how many individual boosters could be built out of the available casings, nozzles, etc.)? Would/is there a consideration of replacing the segment casings with composites?

A) NASA does not respond to hypothetical questions.

4) What is the likelihood of switching to HTPB?

A) There are no plans to switch to HTPB for Ares I flights. HTPB remains a possible upgrade under study for later Ares V flights.

5) What are the main purposes of the Ares 1-X test?

A) The Ares I-X test flight, scheduled for April 2009, will be a suborbital development flight test. Ares I-X will give NASA its first opportunity to demonstrate and collect key data on: roll and overall vehicle control, staging/separation, vehicle integration, assembly and launch operations, aerodynamics and loads and 1st stage re-entry dynamics for recovery.

6) How much of the first stage is drawn from unmodified STS components?

A) The current design motor is a combination of existing (e.g., motor cases, aft skirt, TVC, etc), modified (e.g., propellant grain, etc.), and new hardware (e.g., forward structures, etc.), with the majority of components falling within the first two categories.

7) Have the assumptions that formed the basis for the ESAS conclusions (with respect to Ares-1/Ares-V) changed enough that they are no longer completely valid? That is, since the SSME cannot be air started, and since the 5 segment SRB is required, would it be prudent to revisit previously discarded options, or consider new ones?

A) No. ESAS was a study conducted in 60 days, representing a summary of years of exploration architectural studies. Since that study was concluded, over two years ago, the Constellation Program has evolved the architecture.

8) What are the top three concerns being worked on the Ares 1 first stage at this point? (Adding our current list as currently claimed – feel free to dismiss any/all)
Roll moment – Is the vehicle controllable?
Overall loads for structural design / weight?
Vibe environment as it relates to upper stage, instrument unit and Orion loads, especially to J-2X propellant conditioning at start?
Characterization of lower frequency thrust oscillation and coupling with full-stack modes?
TVC and extended nozzle?
On pad stabilization mechanism?
Efforts to decrease processing time?
Efforts to improve reliability numbers?

A) The Ares I First Stage design effort is going forward consistent with what we would expect at this point. There have been no major surprises. We do track and manage risks – currently, our top risks center around completing the integrated requirements allocation and our ability of heritage hardware to meet Ares requirements.

9) Why is the 5 segment SRB so expensive to develop? Do you have an opinion on Direct, especially given it’s a rehash of a former Marshall project?

A) Our analysis has shown the current Ares I and V architecture to be the lowest life cycle cost solution combined with the highest crew safety/reliability that meets our architectural requirements. NASA has assessed ‘Direct’ type options in the past. They fall short of performance requirements needed for lunar missions, have lower crew safety/reliability projections and higher up-front costs.

10) What’s the status of the tumbling of the first stage after sep (there were notes of concerns relating to the stage returning like a lawn dart)?

A) Starting last year we conducted a series of wind tunnel tests on re-entry/recovery which showed that the 5 segment system was recoverable using an approach derived from the Space Shuttle. We are still developing a full understanding of the recovery attributes which will inform our design.

11) How have the various iterations/mutations of the second stage and Orion over the past year affected the first stage? How much interaction is there between the first and second stage programs?

A) Various iterations have not affect the first stage. There is significant interaction.

12) What is your ‘opinion’ of the Ares performance/Orion weight issue? Is this a problem with Ares performance, or is it a problem with Orion weight? Does you consider the two problems linked? Considering your answer, what is the best (or most likely) solution – cutting weight, or improving performance?

A) Mass and performance trades are a normal part of the formulation process of such a program. Ares is working closely with the Orion team to optimize solutions for the integrated stack.

Selection of L2 Resources For Ares I, V and Constellation: Superb Ares I Launch Ascent Abort Test CGI Video. Integrated Stack (IS) Technical Interchange Meeting (TIM) – Nov 6 to Nov 15. The full ‘8th Floor News’ – Constellation Update (performance issues) – Nov 5. Ares I Mobile Launcher PMR.

‘Proposed’ Ares I SRBSF (Mini VAB) and graphic. LSAM (LDAC-1) Video and Images. Several Constellation All Hands Videos and Presentations. Ares I Pad Rollercoaster (Old and New presentation and slides – the very cool ‘CGI ride on the Ares pad coaster’ video AVAILABLE NOW. Ares I VAB ‘In-Line’ Stacking presentation slides. Live updates on status of changes to Ares I first stage aft.

Presentation of Ares/Orion impacts relating to Shuttle manifest acceleration. Ares I Interstage diagrams. Ares V Super Crawler. Ares I Launch Pad images (ML etc.) Hi Res images of Ares I-X Upper Stage. Orion 606-7 Data Updates. Updates Constellation launch schedule through to Orion 15. Orion Seat test photos. New ML Graphic and info. New Ares V graphic and baseline data. Large collection of hi res Orion paracute drop tests. SIX Part Series of Ares I Upper Stage Graphical Overviews. DAC-1C DDD Vast Slides on Vehicle Design. ATK First Stage Presentation. 39B Lightning Towers Slides. DAC-1C Departure points to DAC-2 Upper Stage Graphcs (Many Changes).

Orion/CEV Display Layout Presentation (40 pages). ATK figures on the 5-Seg Booster weight for CLV. Weather Shield (Rain Shield) for Orion on the pad. New Super hi-res images of Ares I. ATK Cutaway graphics of Ares I – perspective and axonometric – Feb 1. Ares I/Orion CxP 72031 Requirements Validation Matrix Information. CEV Paracute Assembly System (CPAS) Presentation.

Orion Launch Abort System (LAS) overview presentation. Major changes to Ares I Upper Stage – expansive details and data. Ares I/Orion CxP 72031 Requirements Validation Matrix Information. Saturn Twang Test Video for use with Ares I-X. CLV Umbilical Trade Matrix XLS.

Vehicle interfaces for the DAC 1C version of Orion Ares – Jan 3. Ares I-1R Test Flight Plan (full outline) Presentation. Ares I-X timeline and modification expanded info. Ares I troubleshooting latest. Ares I Reference Trajectory. Boeing’s STS to Ares – Lessons Learned Presentation. Latest Ares I and Ares V baseline Configuration image and data. CLV DAC-1C (Changes to CLV Upper Stage).

Ares I-X: Four Seg+Dummy ‘Tuna Can’ stage. Ascent Developmental Flight Test Presentation. CLV Pad 39B Handover Info and Latest. New images of CLV on top of new MLP and LUT. Lockheed Martin CEV/Orion Updates. Constellation news updates. ATK figures on the 5-Seg Booster weight for CLV.

90 Minute Video of Constellation all hands meeting. CLV TIM Meeting Information. CLV/CaLV Infrastructure, Timelines and Information. Escape System Trade Study Presentation.

CEV-CLV Design Analysis Cycle Review (DAC-2) Presentation. Constellation SRR updates. CLV Stick – Troubleshooting/Alternatives/Updates. New CEV Images (include abort mode). Flight Design and Dynamics Division CEV update. CLV Mono-propellant RCS system. CEV pressurisation system review. CLV/CEV Configuration Images. The 2×3 Seg SRB Crew Launch Vehicle Option Presentation…plus more.

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