Overweight Orion may result in landing solution

Engineers are continuing to work through additional solutions for the overweight Orion, as the vehicle heads into the season of Preliminary Design Reviews (PRDs).

Saving mass on Orion – mainly due to a lack of performance from Ares I – is challenging engineers to come up with a variety of changes to the vehicle, one of which – a potential refinement to Orion’s airbag system – may actually hold the potential to return to nominal land landings.

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**ARES I / ORION LIVE UPDATE PAGES**

**ARES V / Mars LIVE UPDATE PAGES**

**EXPLORATION ALTERNATIVES (DIRECT, EELV) PAGES**

 
Overweight Orion and Avionics change:

Most of the ‘red’ top risks for the Constellation program relate to Ares I, though they continue to drive requirements on Orion, which – despite recently completing a Zero Base Vehicle (ZBV) effort by the Orion Vehicle Engineering Integration Working Group (OVEIWG) and associated ‘buy back’ of capability – is overweight again.

‘(One) driving issue Orion is working on is mass. They are currently over their limit,’ noted one memo Constellation (CxP). ‘Will have to be resolved by mid April to not impact the PDR date (CxP is currently heading into ‘week 3 of Phase B,’ moving through to the PDR, having completed the work of System Definition Review).

‘Ares has kicked off their season of PDRs and will go on through the remainder of the spring. They’re making very good progress on the integrated launch vehicle.’

The memo is a result of a meeting which was conducted by NASA administrator Mike Griffin, who is known to be very hands on with the Ares/Orion design process. At that meeting, Mr Griffin requested a change to Orion’s avionics system, a change which will result in buying back some of the precious mass for the vehicle.

‘(Mr) Griffin believes that we aren’t using the most modern avionics that we could and are therefore sacrificing power and mass needing to increase cooling capabilities. Team has heard him loud and clear and will discuss avionics subsystem selection to make sure they are being as efficient as possible.’

The mass issues are obviously the priority element that requires mitigation, though Griffin does not appear to be overly concerned, with the memo adding ‘a lot of architectural progress in the last few months and (Mr) Griffin was happy with how those cases (mass and avionics change) weren’t over driving the design.’

Land vs. Water Landings:

As exclusively revealed by NASASpaceflight.com last year, water landings are the current baseline for Orion’s return to Earth. A recent overview of all Integrated Stack (Ares I and Orion) elements – post Technical Interchange Meeting (TIM) – outlined the history behind the change from land to water as the baseline.

‘Land Landing Nominal was established as the Baseline coming out of ESAS (Exploration Systems Architecture Study). (This was) with limited data, (given) the short amount of time available.

‘CEV (Crew Exploration Vehicle) sponsored NESC (NASA Engineering and Safety Center) to conduct independent assessment of early versions of Orion Design Concepts relative to nominal Land Landing.

‘Level II continued to sponsor the NESC assessment against maturing design concepts by Orion and requested particular attention to safety, cost and off-nominal landing as well. Level II/III put considerable efforts into specifying/defining capability, environments and design constraints for Land Landing and associated Site Survey/Assessments, Probabilities, Recovery Options/Infrastructure.

The document shows that Constellation was already looking into the Land Landing vs. Water Landing debate as early as the Summer of 2006, before the decision was taken to change the baseline to a Water Landing.

‘Mass challenges/Performance closure coming out of the OVEIWG had Land Landing scars into the first block of Orion, and did not showing Land Landing in Lunar Architecture Closure Baseline,’ added the presentation.

The resulting Integrated Stack TIM confirmed the need for the Water Landing (both Lunar and ISS), with Land Landing in abort contingency situations, with further information now available on the specifics of the landing scenarios – including the first note on the prime landing site, San Clemente Basin, Orange County, California.

‘ISTIM guidance to modify baseline to Water Landing Nominal and Land Landing Off-Nominal (focus on Pad/Ascent Aborts with specific bounded environments/constraints,’ added the presentation.

‘Nominal Landing: Baseline Water only for nominal landings (ISS and Lunar). San Clemente specified as Prime. Use ability to loiter on ISS as control for bad weather.

‘De-couple landing constraints into landing loads (impact) and recovery limits. Use wave slope as limiter for loads. Assume 2.5 meter wave height limit for recovery. Revisit ‘Significant Wave Height (SWH) requirements. Develop Water Recovery Test Article to determine if 2.5 meter wave high limit can be raised.

‘Contingency: Team to refine specific/narrowed Abort landing environments for contingency (at pad) for Preliminary Design aspects while assessing this design against the broader scope of environments.’

Airbag Re-Design in work – Nominal Land Landing Potential:

L2 has also acquired information on a potential solution to both mass constraints and the ability to possibly return to a nominal Land Landing for Orion, following a recommendation from the Engineering Review Board.

Noted as ‘changing to an airbag solution to meet the contingency Land Landing requirement,’ the new system employs a smaller number of airbags than the concept originally envisioned for nominal land landing. This, as a result, is a lighter system.

Without the requirement of a lower heat shield – that was originally design to be jettisoned – the airbags in the proposed concept are deployed out of the lower conical backshell.

After jettisoning two panels on Orion, the airbags inflate and wrap around the low hanging corner of the heat shield to provide the needed energy attenuation upon landing. Upon landing, the airbags are vented at a specific pressure so that they collapse at a controlled rate to attenuate.

Moving forward as a design, the new system will be tasked with covering the bases of contingency Land Landings, but does hold the potential for allowing the Orion Project to return to nominal Land Landings in the future. This would also go some way to aid the reuse of the Command Module – currently at risk with Water Landings.

This is an ongoing project, and is yet to undergoing detailed analysis, though opening results are classed as promising on the ability to reduce crew loads to an acceptable level.

One notable challenge relates to the requirement for active roll control on the vertical axis – via the RCS (Reaction Control System) – to maintain a preferred orientation with respect to the velocity vector at landing, in order to minimize chance of tumbling.

The use of retro rockets has also been studied, but failed to win any engineering votes on the mass and reliability numbers.

This article is part 1 of a new series of Ares/Orion articles based on documentated engineering processes being carried out on the vehicles at this time.

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

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).