A Space & astronomy forum. SpaceBanter.com

Go Back   Home » SpaceBanter.com forum » Space Science » History
Site Map Home Authors List Search Today's Posts Mark Forums Read Web Partners

Unintended RCS Jet firing



 
 
Thread Tools Display Modes
  #1  
Old August 15th 03, 01:14 PM
Craig Fink
external usenet poster
 
Posts: n/a
Default Unintended RCS Jet firing

An RCS jet has failed ON, not during a flight, but during a simulation. A
simulation that if it had occurred during a flight, would have resulted in
an uncontrolled RCS jet firing. It happened four of five years ago during
training for a flight. They were flying a TAL. At a point just after MECO,
an RCS jet came on just as the flight software began an OPS transition.
During the transition, some of the memory gets overwritten with the new
code for the next OPS, and some of the the memory doesn't. There was a
status word for the RCS jets that didn't get overwritten or reset, so the
RCS jet that was ON before the transition remained ON after the transition.
Essentially, the flight control didn't know that it was still commanding a
jet ON.

As you can imagine, the vehicle began to tumble out of control during a
critical phase of a TAL. Critical because there isn't much time between
MECO and Entry, and a lot of things have to happen in this short time span.

As to what happened during the sim? I believe they stopped the sim to dump
the computers to try to figure out what happened.

If it had happened on the actual flight? I can imagine that the Commander
would have figured out on her own how to fix the problem. It was similar to
what happened during Gemini, where if something wasn't done very quickly,
the vehicle would have continued to spin up.

Craig Fink
  #2  
Old August 15th 03, 03:10 PM
James Oberg
external usenet poster
 
Posts: n/a
Default Unintended RCS Jet firing


V-E-R-Y interesting, thanks for the report! I'm looking forward to hearing
more details on this pretty amazing event. Frankly, I'm surprised, because
the 'saw-tooth' command form was adopted in the early 1980s to preclude
exactly this kind of failure. Can you estimate the year of the event a
little more closely so I know who to ask for corroboration?



"Craig Fink" wrote in message
hlink.net...
An RCS jet has failed ON, not during a flight, but during a simulation. A
simulation that if it had occurred during a flight, would have resulted in
an uncontrolled RCS jet firing. It happened four of five years ago during
training for a flight. They were flying a TAL. At a point just after MECO,
an RCS jet came on just as the flight software began an OPS transition.
During the transition, some of the memory gets overwritten with the new
code for the next OPS, and some of the the memory doesn't. There was a
status word for the RCS jets that didn't get overwritten or reset, so the
RCS jet that was ON before the transition remained ON after the

transition.
Essentially, the flight control didn't know that it was still commanding a
jet ON.

As you can imagine, the vehicle began to tumble out of control during a
critical phase of a TAL. Critical because there isn't much time between
MECO and Entry, and a lot of things have to happen in this short time

span.

As to what happened during the sim? I believe they stopped the sim to dump
the computers to try to figure out what happened.

If it had happened on the actual flight? I can imagine that the Commander
would have figured out on her own how to fix the problem. It was similar

to
what happened during Gemini, where if something wasn't done very quickly,
the vehicle would have continued to spin up.

Craig Fink



  #3  
Old August 15th 03, 03:35 PM
Craig Fink
external usenet poster
 
Posts: n/a
Default Unintended RCS Jet firing

Hi James,

I could be wrong, but I'm pretty sure it was just prior to Eileen Collins'
first flight as Commander (STS-93) and she was the one who found the bug.
It had been there many many years. It just took the right set of
circumstances for it to be found.

Just goes to show that all the simulations that NASA performs on the flight
software is really worth it.

It also show, that no matter how much testing and verification is done,
there can always be some unique path through the software that can cause a
problem. A problem that may require some human intervention.

If the computer is still commanding a 'saw-tooth' the RCS jet will think
it's a valid command, it would just protect more of a wiring failure. A
short "ON", not a bad command coming from the computer.

Craig Fink





James Oberg wrote:


V-E-R-Y interesting, thanks for the report! I'm looking forward to hearing
more details on this pretty amazing event. Frankly, I'm surprised, because
the 'saw-tooth' command form was adopted in the early 1980s to preclude
exactly this kind of failure. Can you estimate the year of the event a
little more closely so I know who to ask for corroboration?



"Craig Fink" wrote in message
hlink.net...
An RCS jet has failed ON, not during a flight, but during a simulation. A
simulation that if it had occurred during a flight, would have resulted
in an uncontrolled RCS jet firing. It happened four of five years ago
during training for a flight. They were flying a TAL. At a point just
after MECO, an RCS jet came on just as the flight software began an OPS
transition. During the transition, some of the memory gets overwritten
with the new code for the next OPS, and some of the the memory doesn't.
There was a status word for the RCS jets that didn't get overwritten or
reset, so the RCS jet that was ON before the transition remained ON after
the

transition.
Essentially, the flight control didn't know that it was still commanding
a jet ON.

As you can imagine, the vehicle began to tumble out of control during a
critical phase of a TAL. Critical because there isn't much time between
MECO and Entry, and a lot of things have to happen in this short time

span.

As to what happened during the sim? I believe they stopped the sim to
dump the computers to try to figure out what happened.

If it had happened on the actual flight? I can imagine that the Commander
would have figured out on her own how to fix the problem. It was similar

to
what happened during Gemini, where if something wasn't done very quickly,
the vehicle would have continued to spin up.

Craig Fink


  #4  
Old August 15th 03, 03:40 PM
Craig Fink
external usenet poster
 
Posts: n/a
Default Unintended RCS Jet firing

Jon Berndt wrote:

"Craig Fink" wrote in message


An RCS jet has failed ON, not during a flight, but during a simulation.

A

Which simulator?


I'm pretty sure it was the SMS. I wasn't involve with the simulation, just
verifing the fix.

Craig Fink
  #5  
Old August 15th 03, 07:27 PM
external usenet poster
 
Posts: n/a
Default Unintended RCS Jet firing

Craig Fink wrote in message thlink.net...
Hi James,

I could be wrong, but I'm pretty sure it was just prior to Eileen Collins'
first flight as Commander (STS-93) and she was the one who found the bug.
It had been there many many years. It just took the right set of
circumstances for it to be found.

Just goes to show that all the simulations that NASA performs on the flight
software is really worth it.

It also show, that no matter how much testing and verification is done,
there can always be some unique path through the software that can cause a
problem. A problem that may require some human intervention.

If the computer is still commanding a 'saw-tooth' the RCS jet will think
it's a valid command, it would just protect more of a wiring failure. A
short "ON", not a bad command coming from the computer.

Craig Fink





James Oberg wrote:


V-E-R-Y interesting, thanks for the report! I'm looking forward to hearing
more details on this pretty amazing event. Frankly, I'm surprised, because
the 'saw-tooth' command form was adopted in the early 1980s to preclude
exactly this kind of failure. Can you estimate the year of the event a
little more closely so I know who to ask for corroboration?



"Craig Fink" wrote in message
hlink.net...
An RCS jet has failed ON, not during a flight, but during a simulation. A
simulation that if it had occurred during a flight, would have resulted
in an uncontrolled RCS jet firing. It happened four of five years ago
during training for a flight. They were flying a TAL. At a point just
after MECO, an RCS jet came on just as the flight software began an OPS
transition. During the transition, some of the memory gets overwritten
with the new code for the next OPS, and some of the the memory doesn't.
There was a status word for the RCS jets that didn't get overwritten or
reset, so the RCS jet that was ON before the transition remained ON after
the

transition.
Essentially, the flight control didn't know that it was still commanding
a jet ON.

As you can imagine, the vehicle began to tumble out of control during a
critical phase of a TAL. Critical because there isn't much time between
MECO and Entry, and a lot of things have to happen in this short time

span.

As to what happened during the sim? I believe they stopped the sim to
dump the computers to try to figure out what happened.

If it had happened on the actual flight? I can imagine that the Commander
would have figured out on her own how to fix the problem. It was similar

to
what happened during Gemini, where if something wasn't done very quickly,
the vehicle would have continued to spin up.

Craig Fink


it can be done with hardware, too. www.gusgrissom.com
  #6  
Old August 15th 03, 10:01 PM
John Maxson
external usenet poster
 
Posts: n/a
Default Unintended RCS Jet firing

wrote in message
om...

it can be done with hardware, too. www.gusgrissom.com


In the case of Mission 51-L, the firings observed from lift-off
through t+58 seconds were discrete (on-off, bang-bang).

Even the continuous, right-aft, yaw firings (beginning at about
t+59 seconds) stopped briefly prior to the terminal firings.

--
John Thomas Maxson, Retired Engineer (Aerospace)
Author, The Betrayal of Mission 51-L (www.mission51l.com)


  #7  
Old August 15th 03, 10:07 PM
James Oberg
external usenet poster
 
Posts: n/a
Default Unintended RCS Jet firing


"John Maxson" wrote in message
...
wrote in message
om...

it can be done with hardware, too. www.gusgrissom.com


In the case of Mission 51-L, the firings observed from lift-off
through t+58 seconds were discrete (on-off, bang-bang).

Even the continuous, right-aft, yaw firings (beginning at about
t+59 seconds) stopped briefly prior to the terminal firings.

--
John Thomas Maxson, Retired Engineer (Aerospace)
Author, The Betrayal of Mission 51-L (www.mission51l.com)




  #8  
Old August 16th 03, 04:24 AM
Roger Balettie
external usenet poster
 
Posts: n/a
Default Unintended RCS Jet firing

"John Maxson" wrote:
In the case of Mission 51-L, the firings observed from lift-off
through t+58 seconds were discrete (on-off, bang-bang).


Please provide telemetric evidence of these "observed firings".

Even the continuous, right-aft, yaw firings (beginning at about
t+59 seconds) stopped briefly prior to the terminal firings.


Please provide telemetric evidence of these "right-aft, yaw firings".

Please define "terminal firings".

Evidence and definitions will provide a common ground on which we can
discuss your claims.

Roger
--
Roger Balettie
former Flight Dynamics Officer
Space Shuttle Mission Control
http://www.balettie.com/


  #9  
Old August 16th 03, 04:22 PM
external usenet poster
 
Posts: n/a
Default Unintended RCS Jet firing

"Roger Balettie" wrote in message m...
"John Maxson" wrote:
In the case of Mission 51-L, the firings observed from lift-off
through t+58 seconds were discrete (on-off, bang-bang).


Please provide telemetric evidence of these "observed firings".

Even the continuous, right-aft, yaw firings (beginning at about
t+59 seconds) stopped briefly prior to the terminal firings.


Please provide telemetric evidence of these "right-aft, yaw firings".

Please define "terminal firings".

Evidence and definitions will provide a common ground on which we can
discuss your claims.

Roger


Roger, please comment on the S-11 rcs A&C roll switch. show
us that you know something about flight dynamics.
  #10  
Old August 16th 03, 06:37 PM
Jay Windley
external usenet poster
 
Posts: n/a
Default Unintended RCS Jet firing


"James Oberg" wrote in message
news |
| What's "S-11"? At least, give us a clue which decade -- maybe, which space
| program -- you're referring to?

Jim, he's talking about Switch 11 on Panel 8 of the Block I command module
in which his father unfortunately perished. Scott claims that switch was
intentionally sabotaged with a small piece of metal, creating a short
circuit which caused equipment to intentionally overheat and start the
Apollo 1 fire.

Needless to say, none of his claims stands up to much scrutiny.

--
|
The universe is not required to conform | Jay Windley
to the expectations of the ignorant. | webmaster @ clavius.org

 




Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Unintended RCS Jet firing Craig Fink Space Shuttle 20 August 17th 03 05:56 PM


All times are GMT +1. The time now is 01:50 AM.


Powered by vBulletin® Version 3.6.4
Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Copyright ©2004-2024 SpaceBanter.com.
The comments are property of their posters.