Chief Engineer outlines Ares I-X issues – includes Thrust Oscillation

by Chris Bergin

A report from Ares I-X’s Chief Engineer has called for the strengthening of the vehicle’s hardware, due to the red risks associated with Thrust Oscillation near the end of first stage burn – which is also threatening the vehicle’s Flight Termination System (FTS) components.

The vehicle is also requiring mitigation of other multiple issues and concerns – found during the vehicle’s Critical Design Review (CDR) Phase II meeting, though launch remains on track for the Spring of 2009.

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Ares I-X:

Ares I-X is the opening test flight for the Constellation Program (CxP), tasked with gaining data on first stage flight dynamics, controllability, first and second stage separation, and first stage recovery.

The vehicle consists of a four segment booster, dummy upper stage and an Orion boilerplate Crew Module (CM) with Launch Abort System (LAS) simulator.

Hardware is already being constructed for delivery to the Kennedy Space Center (KSC) for what is currently scheduled as an April, 2009 launch from Pad 39B.

Due to previous realignment of the shuttle schedule, relating to dual flows in the VAB for STS-125 and the supporting STS-400 (Launch On Need), this date is being threatened by around a six week delay.

Among the hardware being built is the “Party Hat” – which consists of a boilerplate Orion CM and Launch Abort System Simulator. The Integrated Product Team (IPT) at the Langley Research Center (LaRC) is planning to ship the hardware to KSC in November.

“The CM/LAS team, at LaRC, is targeting November 19 as the shipment date to KSC, not withstanding the overall system integration activities and schedule margin,” noted a special status presentation.

“The CM/LAS IPT has an aggressive schedule and plans to complete major piece part fabrication by the end on August 2008.”

Work is also progressing on the first stage forward skirt, Roll Control System (RoCS) modules on Interstage One (IS-1), the lightning tower that will be added to the top of the Fixed Service Structure (FSS) of Pad 39B and Vehicle Assembly Building (VAB), High Bay (HB) work – pending STS-125 associated restrictions.

Ares I-X High Bay 4 operations inside the VAB are currently scheduled to begin on October 23.

However, despite the original constraint of STS-125 related operations being a driver for Ares I-X’s preparations at KSC, the presentation from Ares I-X’s Chief Engineer has noted concerns with regards to the speed the teams are having to work to make the review dates ahead of the test flight.

“Concerns are the working group approach and the speed at which everything is happening,” the presentation noted. “Overlapping meetings and multiple demands have and are impacting ability to support all reviews and meetings.

“Aggressive Schedule, overlapping reviews and undefined future work continue to make it difficult to provide adequate review coverage.”

A more solid launch date is expected at the end of the year.

Ares I-X Chief Engineer Review:

The Chief Engineer’s comments were part of an expansive presentation outlining the Ares I-X System Critical Design Review (CDR) Phase II meeting that took place this week.

The CDR Panel meeting was used to review open items from the CDR Phase I meeting in March, allowing for the team to complete a dry run and documentation to meet the review’s entrance criteria.

The focus was on significant topics such as Guidance, Navigation and Control (GN&C), the design of the First Stage Avionics Module (FSAM), vibro-acoustics, coupled loads, qualification status, and the integrated hazard assessment.

While this CDR process will conclude in August 2008 – with an outbrief to the Constellation Program Manager – the Chief Engineer created a stand-alone presentation based on his “perspective”.

“Overall Design Process: Outstanding progress since CDR Phase I: Great support among IPTs and SE&I (NASA’s Systems Engineering and Integration),” opened the presentation. “Issues are being worked. Old issues are being retired.”

However, the Chief Engineer the outlined his “Top Issues List” – which noted one “RED”, one “AMBER”, and five “YELLOW” concerns, with the RED element – as seen with Ares I – centralized on “vibroacoustics environments” – specifically Thrust Oscillation (TO) related concerns with the vehicle’s hardware and components.

“Assessments of vibroacoustics environments: Current assessments show higher results, some questions on the wind tunnel forcing function (traveling wave) provided, looking at possible approaches to lower loads: e.g. STEL (static aeroelastic) loads in the combination loads equation – maximum vs statistical approach.”

Though not explained, it is possible that engineers estimated their data with the maximum parameters in mind, before attempting to trade conservatism and reduce the calculation for accuracy and positive margins – which is a usual engineering practise.

However, Thrust Oscillation is specifically named in relation to end of the first stage burn of Ares I-X, which requires mitigation – proposed to be in the form of high strength fasteners.

“Preliminary results show lower axial loads and higher lateral loads during thrust oscillation at the end of the FS (First Stage) burn (T+120sec). Proposed mitigation (high strength fasteners in impacted hardware) in work, needs to be presented at ERB (Engineering Review Board).

“Reported FS negative margins of safety for Load Cycle 2 (LC2) results. Does not include latest USS (Upper Stage Simulator) corrected ballast model – requires an assessment by SE&I and USS for impacts.”

While beefing up the structure is a mitigation for the hardware, Ares I-X’s components are also in the TO firing line, with the most concerning element referencing the Flight Termination System (FTS) – which may require a range waiver due to the potential TO could exceed the components certification, and the threat of vibrating them out of action.

“Requirement – Range Safety: multiple waivers. Lack of dual S&A device. Lack of initiation of LSC at both ends. Lack of “CRD Self-test” capability. Minimum separation of FTS components,” added the presentation.

“Requirement: FTS Range frequency – using current Air Force waiver. FTS Components environments exceeded at T+110 seconds – end of burn (Thrust Oscillation condition).”

A surprise mention is also made on the threat of four segment first stage diving nose first into the ocean. Such a re-entry would see the stage racing back to Earth, with the parachutes useless, before smashing into the ocean. This would likely result in the stage being destroyed on impact.

However, the concern only relates to this undesirable return being found in a small percentage of simulated test runs – called Monte Carlo runs. This type of re-entry was previously reserved as a concern to the five segment first stage of the Ares I vehicle.

“FS (First Stage) Recovery Analysis Updates: Current analysis shows 2 percent and 9 percent of the Monte Carlo runs have nose first reentry,” added the Chief Engineer’s first “YELLOW” risk. “FS working on percentage of possible structural failures for nose first reentry. Risk acceptance needed.”

Other concerns listed in the presentation relate to Rollout Stabilization, Heritage hardware (Peacekeeper) used in a different configuration/environment, Telemetry Architecture (and the need for additional range system hardware), an issue with the Roll Control System interface on the Interstage, and the aforementioned schedule.

The Chief Engineer also noted concerns with the use of Atlas avionics software to control Shuttle and Peacekeeper heritage and new hardware, citing “Risk Needed” with the associated paperwork.

Shelf life of Ares I-X hardware also gained a mention, which require either waivers or formal acceptance of risk.

“BDM/BTMs (Booster Decel Motor/Booster Tumble Motor): Beyond shelf life – need formal acceptance of Risk. Not qualified for Ares I-X environments – waiver being considered.

“RoCS (Roll Control System) pyro valves. Beyond shelf life – need formal acceptance of Risk. Not qualified for Ares I-X environments – looking at testing and a CR (Change Request), waiver being considered.

“Aft RRGU (Redundant Rate Gyro Unit) Qualification testing. Concern would be that the Aft RRGU doesn’t pass the qual test and would require a new control algorithm approach if aft RRGU is eliminated – schedule risk.

“Requirement Changes – Schedule Risk (moved from issues chart). Requirements updated – 1st bending mode frequency range change – concern is if the FTV (Flight Test Vehicle) comes in lower then 1.2 hz which would require update to control algorithm and additional testing. Plan being developed to address this concern if this happens.

“Change in verification of joint stiffness from testing to analysis – added risk (modeling of joints not test verified for loads and dynamic analysis) – Integrated Modal testing to help with determining critical mode shapes and frequency for control.”

The Chief Engineer’s closing remarks emphasized the need for the mitigation of all the concerns raised in his presentation, by next April.

“Forward plans are in work to resolve open issues and reduce the risk to flying in 2009. This will be accomplished with analyses, testing, the verification process and culminating in the DCR/Hardware Acceptance Reviews. Waivers and Deviations will be a last resort but will be necessary to fly by April 2009.

“Mitigation of issues, concerns and risks are the key to success of Ares I-X.”

Selection of L2 Resources For Ares I, V and Constellation: 

Ares I Rollercoaster Car mockup photos. Ares I-X CDR Presentations. Ares Test Schedule Presentation. Full (and very expansive) set of presentations on Ares/Orion mass and status report. Ares I ‘Parasorber’ TO migitation hardware presentation and animation. Ares I TO Risk Slides. Ares I Risk Status.

Hi Res Images of Ares I FS Parachute Test Vehicle (JDTV). 20mb of new Lunar Images of Chariot, Athlete and Lunar Crane. Ares I KSC Processing Master Book – 184 pages. Changes for Ares I-X (Images). PRCB Transition Presentation (Shuttle to Ares). Ares V (5.5/6xRS-68) Presentation (and more). Orion Parachute Vehicle Images. Latest Risk Matrix for Ares. SI Unit Directive Document. CxP PMR08 Manifest. PDR and associated notes from CPCB meeting. Orion Parachute Test Vehicle (PTV) Photographs.

110mb worth of Ares I-X Weekly Test Presentations (Ares I-X, J2-X etc. up to end of April) The Orion LIDS (Low Impact Docking System) Section (Images, Videos, Engineering Notes). Hi Res Images of Ares I in the VAB. Ares I-X Integrated Milestone Charts. Ares I Thrust Oscillation Focus Team Status Presentations (over 50mb – includes DTO on Shuttle missions), Ares I-X Global Buckling Status Presentation, Ares I – Launch Pad Stabilization and Damping Presentation, Ares I: Purge/Vent/Drain and Vehicle Access Presentation.

Ares Tilt Up Umbilical Arm (TUUA) Test – Video, Ares/Orion Comm and Tracking Presentation, Ares I Nozzle Extension Update Presentation, Ares/Orion Integrated Stack TIM Summary (Major Issues) Presentation, Orion Land vs Water Landing Update + Crew Survival (post 36 hrs) Presentations.

Altair Overview Presentation. Ares I Risks and Status. Ares I-X Booster Recovery Images and Video. Ares I-X Pad Images. Ares I-Y Mission Overview Video (50mb – Superb).  Orion Lunar Transit CGI Video. (Several more videos, including first video of Orion splashdown). 

Orion Rendezvous with the ISS CGI Video, plus AERCam Inspections. Ares I Thurst Oscillation Update Section.  Images of completed PA-1 boilerplate Command Module at LaRC.  CxP Planning for Architecture Closure – Feb 19. Ares V Overview Presentations. Other Major CxP Updates for Feb (List restricted to L2).

Orion 607 Overview Presentation (Jan 08), Constellation Program Status/Budget and new Manifest to Orion 20 Presentation (Jan, 08). Michoud Transition to Ares I/V (Jan 17, 08). Several MLAS (Max Launch Abort System) Presentations. Over 60 Hi Res Images of Orion Mock-up at JSC (Hatch, Seats, Flight Deck) – December.

Lunar Habitat Assembly. PRCB Presentations on hardware and infrastruction transition (from Palmdale to MLP Park) ‘Follow live’ Lightning Towers Construction images. Latest Mobile Launcher details. Orion/Ares I/Delta IV Heavy NEO Feasibility Study (Video). Constellation EVA Study Presentation. Superb Gene Kranz address to CxP workforce (Apollo to Orion feature) video. MOD ‘LEO to Mars’ presentations.

Superb Ares I Launch Ascent, Pad Abort Test CGI Videos (three). Integrated Stack (IS) Technical Interchange Meeting (TIM) notes – 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. Ares I VAB ‘In-Line’ Stacking presentation slides.

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. Ares I/Orion CxP 72031 Requirements Validation Matrix Information. CEV Paracute Assembly System (CPAS) Presentation.

Orion Launch Abort System (LAS) overview presentation. Changes to Ares I Upper Stage – expansive details and data. Ares I/Orion CxP 72031 Requirements Validation Matrix Information. CLV Umbilical Trade Matrix XLS. Vehicle interfaces for the DAC 1C version of Orion Ares. Ares I-X Test Flight Plan (full outline) Presentation. Ares I-X timeline and modification expanded info. Ares I Reference Trajectory. Boeing’s STS to Ares – Lessons Learned Presentation. 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. ATK figures on the 5-Seg Booster weight for CLV.

90 Minute Video of Constellation all hands meeting. Escape System Trade Study Presentation. CEV-CLV Design Analysis Cycle Review (DAC-2) Presentation. 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 much more (L2 Constellation over 190,000mb in size).

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