Orion PDR date slips – Off-nominal Orion landing concern evaluated

Orion’s next key milestone, the Preliminary Design Review (PDR), has been delayed to November 21 – a slip which ripples through all the way through to the Design Certification Review (DCR) in 2013, according to May 6 documentation.

Meanwhile, engineers have been evaluating crew survival scenarios, should Orion suffer an off-nominal landing. A baseline plan calls for astronauts to survive in the capsule for up to and over 36 hours prior to rescue – which is currently a concern.

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

**ARES I LIVE UPDATE PAGES**

**ORION/Exploration Vehicles LIVE UPDATE PAGES**

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Orion PDR Slip:

Orion’s PDR was originally scheduled to take place on September 26. A change to the avionics system and on-going mass challenges were not – according to NASA administrator Mike Griffin recently – ‘over driving the design,’ with budgetary problems now believed to be adding strain to the program.

‘(One) driving issue Orion is working on is mass. They are currently over their limit,’ noted one memo Constellation (CxP) last month ‘Will have to be resolved by mid April to not impact the PDR date.’

However, that date has now slipped, following a CEV Project Control Board (CPCB) meeting on May 6.

‘Proposes to baseline the following changes: PDR moved to 11/21/08 (from 9/26/08), CDR (Critical Design Review) moved to April 2, 2010 (from 9/25/09), DCR moved to 3/15/13 (from 1/18/13),’ noted quotes from the meeting’s associated documentation.

‘The CPCB concurred with the revised PDR schedule as presented. The presentation was made in order to get Project approval of a six week slip in the PDR schedule as well as inform the CPCB of remaining milestones on the schedule.’

‘The revised schedule presented moves PDR Board from 9/26/08 to 11/21/08.’

No specific reason is noted for the slip, and it is understood that several key challenges have combined to move the PDR date, as listed in the CPCB meeting’s minutes.

Those minutes reference Orion’s mass status as a key point of discussion, along with cost threats, ascent and abort loads. ‘Mass Opportunity Development Plan. Orion Cost Threat Mitigation Plan. Integrated Performance Assessment Plan,’ all gain a mention as items discussed in the CPCB meeting notes.

Sources claim the ‘Orion Cost Threat’ element is now causing problems for the Orion Project, and holds a level of responsibility for the PDR slip.

Off-Nominal Orion landing in the sea:

Though unlikely ever to be required, engineers have conducted a study into the ability for the crew to survive inside the capsule, should the vehicle suffer an off-nominal landing, which led to the astronauts enduring an extended period of time inside Orion prior to rescue.

The study shows that the current Orion vehicle has ‘difficulty in meeting 36 hour post-landing requirement in the water,’ even if such a scenario – where the crew were stranded for such a long period of time – is unthinkable.

However, engineers are not taking any chances, notably if Orion suffers an off-nominal landing, far away from sea lanes, in a potentially hostile territory, likely coupled with a loss of tracking and communications.

Noted as a requirement, ‘Orion shall provide from crew survival, without permanent crew disability, for at least 36 hours with the hatch closed in sea state conditions defined for landing in the water.’

**CLICK IMAGE for video clip of Orion splashing down in the sea (part of a full mission overview video for Ares/Orion testing, available in full on L2**

Those defined conditions note a maximum sea surface temperature of 36 degrees C, coupled with max sea state (unspecified). These conditions have recently been further defined.

‘Agreement reached as a result of DAC (Design Analysis Cycle) and formally approved: Changed max sea surface temperature to 31 degrees C, and decoupled from maximum sea state (undefined),’ noted the associated presentation.

‘Excludes only Persian Gulf and Red Sea in local summer, 0.08 percent change of random landing in these locations. (However), even with these changes, the baseline Orion vehicle is non-compliant with the requirement for 36 hours in certain off-nominal warm temperatures, if crew stays suited and inside the vehicle.’

Interestingly, the main concern for a stranded crew inside Orion is the heat, and once again mass issues with Orion is proving to be one of the associated challenges.

‘Primary issue is elevated crew body temperature. Cold environments are not a concern, due to well insulated vehicle and suits. Current design of Command Module has very limited power and mass available for cooling,’ added the presentation.

‘Current design provides only 15 minutes of active thermal control (cooling) available after landings. Snorkel fan used for 36 hour period to provide CO2 control and minimal ventilation.’

As a mitigation procedure for increased body temperature, the crew would be required to immediately remove their entry suits, and even exit the vehicle whilst awaiting rescue. However, that too has its own constraints.

‘To keep crew from exceeding max core body temperature, crew would need to doff suits and possibly egress vehicle for sea surface temperatures between 19 C and 31 C.

‘Allowable for up to 70 percent of random off-nominal landings. Max significant wave height state in these conditions is 4 meters (13.1 feet).

‘Open issues with analysis: Analysis did not account for thermal soakback, day/night extremes, and sun on the vehicle, which can make the story worse. Also assumed ACES suit is more insulated than Constellation suit – which is expected to make the story better.’

Evaluations will continue – and a forward plan is expected in the first half of this year – which will include increased cooling and associated impacts to meet current requirement.

It is understood that this is one of the issues raised by certain sectors of the engineering community that are opposed to water landings being the baseline for Orion – along with the Astronaut Office – which could form added pressure for the Orion Project to re-install land landings as the baseline.

This article is part 5 of a new series of Ares/Orion articles based on documentated engineering processes being carried out on the vehicles at this time. Click for: **Part 1** – **Part 2** – **Part 3** – **Part 4**

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).