Tuesday, 7 July 2009

Constellation is looking Increasingly Shaky

The news about the Constellation program, comprised of the Ares-1 booster and Orion spacecraft just keeps on getting worse.
From NASA Spaceflight.com :
...Ares I-X has four major issues - one of which relates to the continually slipping launch date, and three related to technical issues. Levels of ‘risk’ range from the smallest on the 25 box risk matrix, noted as 1×1 (GREEN), to the highest, seen as 5×5 (RED) - which list the ‘Likelihood’ the issue would occur x severity of ‘Consequence’ such an issue would have on the vehicle.

Interestingly, Thrust Oscillation (TO), even on the Ares I-X four segment - as opposed to the well know issues with the Ares I five segment - first stage dominates Ares I-X’s Top Risks findings.

This is despite warnings from the Ares I-X Chief Engineer over a year ago - as reported by this site - that TO and vibro-acoustic effects on the vehicle’s Flight Termination System (FTS) required mitigation.

Requirement: FTS Range frequency - using current Air Force waiver. FTS Components environments exceeded at T+110 seconds - end of burn (Thrust Oscillation condition),” wrote the Chief Engineer on his expansive presentation (available on L2) to the Ares I-X System Critical Design Review (CDR) Phase II meeting in June, 2008.

Yet on the June 22, 2009 “Top Risk” review, “Thrust Oscillation and its affects on the Flight Termination System (Range Safety),” is classed as a 4×5 risk, showing it’s actually increased as a concern.

That increase is related to the time of ascent where TO’s effects on the vehicle’s FTS exceeds rated vibrational input levels, now deemed as starting around T+70 seconds - not T+110 seconds - into flight.

This in turn has placed pressure on obtaining the required Air Force waiver for the range, without which, Ares I-X would not be allowed to launch.

Another waiver will be required on the second “Top Risk” - related to Thrust Oscillation effects on the first stage TVC (Thrust Vector Control) electronics, used to gimble the solid rocket motor’s nozzle during steering commands. This risk, which is listed as 3×5, makes its debut on the Top Risk list.

However, a waiver on this issue is understood to be less of a problem to acquire, due to the knowledge of the “stock shuttle legacy SRB TVC system”, which Ares I-X will be using.

The biggest risk, a 5×5 risk, relates to the “vibro-acoustic environment input to Upper Stage Simulator (USS) exceeding structural margins.”

Very little is noted on this problem, although a recommendation that the USS should receive additional bracing to carry the higher than anticipated loads is noted as an avenue of mitigation. It is not known if that work has already been added to Ares I-X’s processing flow, although no reference has been made on the daily processing notes.
So what does this mean, in simple terms?

That the thing will currently shake itself so badly that it may not work, unless something is done about it. And that "something" will involve extra weight, so much so that it may not work anyway.

Having an unresolved 5x5 risk at this stage of the game is a sign that the whole thing's a mess: because as development goes on, more risks will be found, things we can't predict accurately, just anticipate and plan for by providing safety-margins. The ones originally planned for have all been eaten up, and so now we're de-scoping, winding back requirements, so the thing will do less.
Ares I can launch the ISS version of Orion, thanks to a series of mass stripping exercises - notably the ZBV (Zero Based Vehicle) effort. However, the Lunar Orion’s mass properties - again based on Ares I’s performance capability - is a major challenge, seeing its “score card” mass properties between Orion 606-E (December 2008) and Orion 606-G (May 2009) grow into a RED risk for the program.

Solutions will need to be sought throughout all of the major components on Orion; with the LAS (Launch Abort System), CM (Crew Module), SM (Service Module) and Jettisoned Spacecraft Adapter (SAJ) all trending up in mass - which includes the breaching of the “managers reserves”, set aside for mass growth margins.

Orion is also suffering from problems with its electric power generation and storage margins, which is threatening a redesign of the vehicle’s Solar Arrays/Panels.

According to documentation, the required margins on the ability for the solar panels to generate enough power for storage in the vehicle’s batteries - for use during the Lunar Orion’s flight out of sunlight - is short by 22 percent.

The solutions to this problem would require either an increase in the size of Orion’s solar wings and/or additional battery storage capacity - with both options adding yet more mass to the vehicle. The ISS Orion’s electric power generation and storage margins are understood to be within requirements.
Constellation’s management are taking the crew reduction a stage further, by changing Orion’s capability from 0-6 crew (unmanned capability) to 2-4 crew - with a contingency of no less than one crewmember being able to fly the vehicle. Such a change eliminates Orion’s ability to fly unmanned, which could have been utilized in a number of scenarios.
So now instead of being able to carry a crew of 6, and operate with no crew at all, it can carry at most 4, and will need 1 to re-enter.

I've never been optimistic about the Ares Booster, but I wish my predictions weren't being born out by reality. That's engineering though.

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