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Author
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Topic: [Discuss] NASA's Orion Ascent Abort-2
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Robert Pearlman
Editor Posts: 50516
From: Houston, TX
Registered: Nov 1999
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posted 07-01-2019 08:17 AM
   
Please use this topic to discuss NASA's Ascent Abort-2 (AA-2) test of Orion's Launch Abort System (LAS). |
Robert Pearlman
Editor Posts: 50516
From: Houston, TX
Registered: Nov 1999
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posted 07-01-2019 08:23 AM
Photos of the Orion Ascent Abort-2 stack on Complex 46 taken this morning (July 1), a day before the test flight.Photos credit: collectSPACE  
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David C
Member Posts: 1397
From: Lausanne
Registered: Apr 2012
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posted 07-02-2019 09:18 AM
Call me old fashioned and conservative, but I'd have more confidence in a demonstration that included full parachute deployment. |
Robert Pearlman
Editor Posts: 50516
From: Houston, TX
Registered: Nov 1999
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posted 07-02-2019 09:20 AM
NASA has conducted 59 Orion parachute recovery tests, including in abort configuration and altitude. This test was only focused on the Launch Abort System motors. |
David C
Member Posts: 1397
From: Lausanne
Registered: Apr 2012
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posted 07-02-2019 10:21 AM
Yeah. This was the only test of a "fully active launch abort system", and didn't go to parachute deployment. I don't really consider multiple roll outs from the back of a C-17 to be adequate. Apollo was fully demonstrated. I'm very wary of partial testing of this critical last ditch system.I can't help thinking of the inadequate initial Soyuz parachute testing to give one example. I know we're better now, but this seems to be cheap and "clever." Just demonstrate the whole thing as realistically as possible. |
cspg
Member Posts: 6347
From: Geneva, Switzerland
Registered: May 2006
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posted 07-02-2019 10:30 AM
I was expecting parachutes... strange to see none.Oh, and the image that may last is the one of the LAS falling. A terrifying picture (or hilarious if you're sarcastic). |
ManInSpace
Member Posts: 303
From: Brooklin, Ontario Canada
Registered: Feb 2018
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posted 07-02-2019 04:06 PM
quote:
Originally posted by David C:
Just demonstrate the whole thing as realistically as possible.
I take the same view.Why not just add the parachute package and do a "full-up" live fire test of the Abort and Recovery systems? Pallet drops are a fine step in the testing process, but cannot replicate the conditions deploying under abort conditions. |
Headshot
Member Posts: 1221
From: Vancouver, WA, USA
Registered: Feb 2012
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posted 07-03-2019 07:56 AM
While I am glad the test went as planned, it did not seem that complicated to me. There were no parachutes to deploy, no RCS system to stabilize the test vehicle. What was the pacing item for this test? Was it the LAS itself, which I believe has been tested once before? The booster? Funding? It certainly should not have been a simple boilerplate Orion test article. Why couldn't this test have been performed six to twelve months earlier? |
Robert Pearlman
Editor Posts: 50516
From: Houston, TX
Registered: Nov 1999
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posted 07-03-2019 09:30 AM
As mentioned, this test was focused on the performance of the abort motors. It provided the team with the data needed to understand the abort scenarios throughout the flight. From my conversation with Mark Kirasich, NASA's Orion program manager: This gives us a validation. It anchors the [computer] models. We have these very detailed CFD — Computer Fluid Dynamics — models that model our trajectory, model the abort as the engine fires. We can look at the attitude control system as it fires in great detail. And from these models we learn very interesting things, how the atmosphere — we talk about how the air going by at 600 miles, it actually bends the plumes — and we see that in CFD models. What this [test] does is we will get a set of data points that anchors the models and then gives us more confidence in the rest of the computer models we are doing. Once we anchor the models, we have more confidence to use models to look at the performance during the other possible conditions you would abort from. Of course, such modeling was not available during Apollo, but more so, the Orion LAS is more capable than the Apollo LES. Parachute testing was needed 50 years ago because the LES had no ability to orient the command module — it performed a simple flip and then you hoped the capsule was in the direction you wanted to go. The Orion LAS has an attitude control motor that leaves the crew module in a stable position before the LAS separates. |
Jim Behling
Member Posts: 1815
From: Cape Canaveral, FL
Registered: Mar 2010
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posted 07-03-2019 01:10 PM
quote:
Originally posted by David C:
I'm very wary of partial testing of this critical last ditch system.
And you would be wrong. See AA-1. quote:
Originally posted by ManInSpace:
Pallet drops are a fine step in the testing process, but cannot replicate the conditions deploying under abort conditions.
Yes, they can. The abort conditions do not affect the parachutes. The parachutes don't care if it is a pad, max q or high altitude abort. They end up deploying in the same conditions. quote:
Originally posted by Headshot:
What was the pacing item for this test?
First use of the ATB. First use of LC-46 and this vehicle. Money was programmed for a later test too. |
David C
Member Posts: 1397
From: Lausanne
Registered: Apr 2012
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posted 07-14-2019 12:43 AM
quote:
Originally posted by Jim Behling:
See AA-1
I have no knowledge of any AA-1. Are you referring to PA1? |
oly
Member Posts: 1450
From: Perth, Western Australia
Registered: Apr 2015
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posted 07-14-2019 04:58 AM
quote:
Originally posted by Jim Behling:
The abort conditions do not affect the parachutes. The parachutes don't care if it is a pad, max q or high altitude abort. They end up deploying in the same conditions.
Reviewing the Mercury Program parachute development history would indicate that envelope of aerodynamic conditions that abort systems including rocket motors and parachutes have to work in a wide realm of conditions, something that proved problematic for engineers to overcome. Similar issues were found with the Gemini and Apollo programs. The venting of hypergolic fuel into the Apollo parachute canopy, and the subsequent structural failure, is just one example of how unforeseen conditions can impact the performance of a system. SpaceX and Boeing had also found unforeseen problems with their abort systems that required modification or redesign following testing of the parachute systems. The idea of testing the parachute system as a part of the Orion Ascent Abort-2 test is not a crazy or unnecessary idea, and may have, in this case, been a missed opportunity. I seem to remember that the Orion spacecraft experienced a partial collapse of one of the main parachutes after reentry, and that the main chutes did not fly as designed. |
Jim Behling
Member Posts: 1815
From: Cape Canaveral, FL
Registered: Mar 2010
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posted 07-15-2019 08:44 AM
SpaceX's and Boeing's problems were found in system specific testing and not an abort test.Orion did more parachute tests since EFT-1. Abort test not required for it. |
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