Re: RTLS Story
- From: "Brian Gaff" <briang1@xxxxxxxxxxxxxxxx>
- Date: Sun, 13 May 2007 09:59:31 GMT
This is just an extreme example of what I think many of us have come across
in documentation. Its seems to be nobody's job to sort these things out,
they get passed on by word of mouth and little sticky labels.
I worked in QA and we had a word or two for these. We called them local
adaptations. :-)
Brian
--
Brian Gaff - briang1@xxxxxxxxxxxxxxxx
Note:- In order to reduce spam, any email without 'Brian Gaff'
in the display name may be lost.
Blind user, so no pictures please!
"Danny Deger" <dannydeger@xxxxxxxxxxx> wrote in message
news:46466cad$0$16700$4c368faf@xxxxxxxxxxxxxxxxx
Here is a true story on me training RTLS's as NASA. I hope you like it.
His name is Curt Brown. He is one of the most arrogant and difficult to
get along astronauts in the program. Unfortunately, I didn't know this
during my first training session with him as a student. The training team
planed for a Return To Launch Site, RTLS, abort by killing an engine
shortly after lift off. As expected, there would not be enough power left
in the remaining two engines to make it to an abort orbit, or even to get
across the Atlantic and land in Europe or Africa.
I have decided to attempt to train a Flight Rule I had recently read.
That is if control is shortly after the main engines are turned off on an
RTLS abort, the crew will command a fast separation. I was new to the
field of training astronauts, so I thought they would know to do this
task. I could not have been more wrong.
The rule was written because on an RTLS abort, the shuttle is in
significant atmosphere at the time the engines are turned off. It turns
out the shuttle with the tank on is unstable, but in trim if the attitude
is kept close to the desired zero sideslip angle and -4 degrees angle of
attack. The only devices maintaining control are the small Reaction
Control System, RCS, jets. If the shuttle moves very far from its trim
attitude, the air loads will overwhelm the control available and the stack
will tumble. If this process starts, the best avenue is to get of the
external tank ASAP. After separation, the orbiter by itself is stable and
the flight control surfaces become active.
The problem I had was to do something to cause the combined orbiter and
tank to go out of control right after main engine cut off. I used some
time in the simulator by myself to come up with a way to do this. I came
up with the amount of force to apply, the direction to apply it, and the
duration to apply it. It worked in the simulator by myself. If I applied
the force as soon as the engines turned off, the stack would go out of
control, but after the separation, the shuttle would regain control.
I briefed this to my team lead and got permission to try it in the
training session. I kill the engine shortly after lift off and the crew
goes RTLS at the correct time. The powered flight portion of the RTLS is
flown without incident. As soon as the main engines are turned off, I put
the force in. It did not work as planned. Control was lost as I expected,
but rather that perform the fast separation as called in the flight rules,
the crew engaged the Backup Flight System, BFS. To make matters worse,
there is known bug in the BFS that if it is engaged in this time frame, it
gets lost on what mode it is in and it will not separate from the tank.
Needless to say, entering the atmosphere while still on the tank is a
disaster. The rest of the training simulation was a disaster. The
shuttle tumbled and tumbled. We finally declared the crew dead and
stopped the simulation.
Curt Brown was furious. In the debrief I showed him the flight rule that
says the crew should perform a fast separation in that phase if control is
lost. Curt had never heard of this. I thought it strange that a flown
crew member would never have been trained on such an important rule. The
next day I asked Andy Foster, the lead instructor on ascent abort, about
this rule. Andy informed me this was a bad rule and it should not be
trained. I was stunned. How can we have an official policy to not train
a flight rule? The flight rules are the bible of operating the shuttle -
for both the crew and the flight controllers. I also argued that BFS
should certainly not be an option in this phase if it is known to be
catastrophic to engage.
My complaints fell on deaf ears. Everyone more senior than me was
comfortable having a rule on the books that "everyone" knows we should not
follow. Everyone was also comfortable not training the crew engaging the
backup flight system in this phase - even though it is know to cause
certain loss of orbiter and crew if they do engage.
.
- Follow-Ups:
- Re: RTLS Story
- From: Danny Deger
- Re: RTLS Story
- References:
- RTLS Story
- From: Danny Deger
- RTLS Story
- Prev by Date: Re: RTLS Story
- Next by Date: Re: Orbital night city light visibility
- Previous by thread: Re: RTLS Story
- Next by thread: Re: RTLS Story
- Index(es):
Relevant Pages
|
