"blow the hatches" on Gemini

Jorge R. Frank wrote:

The time doesn't matter; the certainty of detecting the fault does. You
snipped my comparison with a pad abort, in which the countdown is halted
after T-6 seconds. Nevertheless there is practically a zero chance of
actually launching with only two SSMEs running.



Like that "practically a zero chance" part, brings back memories of an
ocean liner and an iceberg.
My pet disaster scenario is that all three SSMEs come up to full power,
the command is given to light the SRBs...
and only one SRB lights.

Pat

On Sat, 03 Jun 2006 15:11:37 -0500, Pat Flannery
wrote:


By and large these are mainly minor glitches- but there are a hell of a
lot of them cropping up on one mission, and that should have been a
warning to all involved.

One reason that these myriad problems weren't taken as a warning sign
fleet-wide is that they were all on Columbia, which was coming off a
two year overhaul. And Columbia had the "Penguin" and "Hangar Queen"
reputation anyway, so the glitches were just taken to be Columbia
being her usual Murphy's Law self. That, and considering that 51J,
61A, and 61B had all gone off very smoothly over the previous few
months, made the "oh my God, the program's at the edge of disaster"
viewpoint very hard to justify.

Brian

Brian Thorn wrote:

They don't start to pressurize the LOX tank for flight until T-2:55.
So really, there was about 2 minutes for the system to figure out
there was a problem and abort. Probably during that time, Launch
Control was looking at the readings, trying to figure out if the LOX
tank was draining or if it was a sensor glitch. Then the computers
aborted the launch from them automatically at T-31, which is the
generic abort point (handover from ground control to vehicle control)
if things aren't right.


Here's the official NSA anomoly report:

"Tracking No Time Classification Documentation Subsystem
MER - 0
None
MET: Prelaunch
GMT: Prelaunch
Problem FIAR
SPR None
IPR None
IFA STS-61C-V-01
UA
PR
MPS
Manager:
Engineer:
Title: Main Propulsion System Liquid-Oxygen (LO2) Inboard Fill-And-Drain
Valve Did Not Close. (This resulted in about 2000 pounds per minute of
LO2 draining from the vehicle through the 8-inch LO2 fill and drain
line.) (ORB)
Summary: DISCUSSION: At launch minus 4 minutes 40 seconds, the
closed-switch indication for the main propulsion system (MPS)
liquid-oxygen replenish valve was not received. Even though the
replenish-valve closed-switch indication was not available, the auto
sequencer continued operation using the valve position indication, the
flowrate, and the actuator pressure to status the position of the
replenish valve. At launch minus 4 minutes 20 seconds, the command to
close the liquid-oxygen inboard fill and-drain valve was blocked in the
liquid-oxygen loading sequencer by the failure of the prerequisite
control logic to receive the mission facility replenish-valve closed
switch indication. This resulted in the auto sequencer initiating a
launch hold. A continue command was issued at launch minus 2 minutes and
55 seconds that allowed the liquid-oxygen terminal-count sequencer to
open the tail-service-mast vent and drain valves without closing the
Orbiter inboard fill-and-drain valve. This unknowingly permitted the
offloading of liquid oxygen until the Orbiter inboard fill-and-drain
valve was noted to be open and manually closed. Liquid-oxygen
prepressurization was initiated; however, the ground helium-gas supply
was unable to satisfy the control-band pressure requirement because of
the ullage-volume increase resulting from the rapid offloading of liquid
oxygen. The tank ullage pressure decreased to -0.12 psid, at which time
the fill-and-drain valve closure allowed repressurization to begin again.
During the liquid-oxygen offloading, the low-level cutoff sensors
temporarily indicated dry. This was probably caused by the termination
of the helium feedline antigeyser injector approximately 20 seconds
after the tail-service-mast drain valve was open. A hold was initiated
at launch minus 31 seconds to review the previous out-of-sequence
loading termination and obtain a 5-minute liquid-oxygen drain through
the main engines. During the hold, the liquid-oxygen main engine
temperature dropped
below the engine start requirement of 168.3 deg R by approximately 3
degrees. The engine limit was exceeded because the amount of liquid
oxygen lost overboard through the fill-and-drain valve caused the
colder, more-dense liquid oxygen to be drawn in from the external tank.
The countdown was recycled to launch minus 20 minutes and oxygen
replenish flow was reestablished. The launch was scrubbed when it was
determined that the vehicle could not be recycled within the allowable
launch window. A liquid-oxygen ullage-pressure of -0.12 psid was
experienced when the liquid-oxygen vent valve was closed, and the helium
supply terminated during liquid-oxygen drain back. Subsequent visual
examination of the liquid-oxygen tank revealed no cracks or debonded
areas. Analysis indicated that with the 98-percent level propellant load
present at the time of occurrence of the negative pressure (-0.2 psi
used for analysis), a safety factor of greater than 1.25 was maintained.
There was no effect on tank cycles. Review of the above-nominal surge
pressure at the engine inlet and the liquid-oxygen manifold was
evaluated because the fill-and-drain valve was closed during flow
conditions (valve not certified to be closed under flow). The surge
pressures observed and the valve opening/closing times all were deemed
acceptable for flight.
CONCLUSION: The MPS liquid-oxygen inboard fill-and-drain valve was not
commanded closed because the liquid-oxygen loading sequencer did not
receive the closed-switch indication from the replenish valve as
required by the prerequisite control logic. The operator verified
replenish-valve closure, but did not close the inboard fill-and-drain
valve prior to issuing the resume command to the automatic sequencer.
CORRECTIVE_ACTION: 1. The prerequisite control logic that blocked the
close command to the liquid-oxygen inboard fill-and-drain valve was
overridden for STS 61-C and STS 51-L. This eliminated the inconsistency
between the liquid-oxygen
loading sequencer software and the prerequisite control software. 2. The
launch commit criteria (LCC) will be changed to verify that the
liquid-oxygen inboard fill-and-drain valve is closed after replenish
valve closure and prior to tail-service-mast vent and drain opening. The
count will be held if the fill-and-drain valve closed-indication is lost
during the remainder of the count down until T-31 seconds. 3. The helium
repressurization "pulse purge" will be turned on if less than 0.25 psi
is read on the liquidoxygen
low-range pressure transducers. The monitoring will be done
automatically with a manual call to pressurize, if required. 4. The
minimum external tank (ET) ullage
pressure rise rate will be verified at T-120 seconds. This rate was
established at 0.85 psi/second as a check on tank-ullage volume, and
therefore, liquid level. The existing ET ullage pressure check has been
removed from T-125 to T-133 seconds to assure compliance with ET
liquid-oxygen tank structural requirements.
EFFECTS_ON_SUBSEQUENT_MISSIONS: NONE

Pat

On Sun, 04 Jun 2006 07:21:14 GMT, in a place far, far away,
(Derek Lyons) made the phosphor on my monitor glow
in such a way as to indicate that:

Pat Flannery wrote:

By and large these are mainly minor glitches- but there are a hell of a
lot of them cropping up on one mission, and that should have been a
warning to all involved.

In reality - that flight description sounds like all four of my SSBN
patrols. When you have a complex vehicle, glitches and minor malfs
are a way of life - only a fool believes otherwise.

Yes, in fact they're exactly what one would expect from "the most
complex machine ever built" (a feature in which they used to take
pride, and possibly still do).

In article ,
Geert Sassen wrote:
...As each hatch actuator finished its
stroke, the movement of the piston uncovered vent ports which released
hot gas into the igniters of the seat propulsion system.
Now that was a novel set-up!

It didn't always work in the correct sequence, i remember reading a
story about one of the seats slamming straight *through* the hatch
during a test...

They did have some debugging to do. :-) That one, if I recall correctly,
resulted from a hot-gas leak, fixed by redundant seals and more careful
quality control on some of the components. The final system was believed
reliable, but it still wasn't anything you'd use unless your life was at
stake...
--
spsystems.net is temporarily off the air; | Henry Spencer
mail to henry at zoo.utoronto.ca instead. |

In article ,
Pat Flannery wrote:
How'd you like to eject straight up into the fouled parawing? That
wouldn't be fun either.

My understanding is that the operational parawing would have used the same
deployment concept as the parachute, meaning that it would deploy with the
capsule nose-up -- putting the ejection path well clear of any possible
snarls -- and the capsule would then flop down into nose-forward position.
Simpler setups were used for some of the development testing but I don't
think they were meant for operational use. (I could be wrong -- it's been
a long time since I read about this.)
--
spsystems.net is temporarily off the air; | Henry Spencer
mail to henry at zoo.utoronto.ca instead. |

In message , Henry Spencer
writes
In article ,
Geert Sassen wrote:
...As each hatch actuator finished its
stroke, the movement of the piston uncovered vent ports which released
hot gas into the igniters of the seat propulsion system.
Now that was a novel set-up!

It didn't always work in the correct sequence, i remember reading a
story about one of the seats slamming straight *through* the hatch
during a test...

They did have some debugging to do. :-) That one, if I recall correctly,
resulted from a hot-gas leak, fixed by redundant seals and more careful
quality control on some of the components. The final system was believed
reliable, but it still wasn't anything you'd use unless your life was at
stake...

Doesn't that apply to _any_ ejector seat? ;-)

In article ,
Jonathan Silverlight wrote:
...The final system was believed
reliable, but it still wasn't anything you'd use unless your life was at
stake...

Doesn't that apply to _any_ ejector seat? ;-)

Yes, but for somewhat less emphatic values of "apply". :-)
--
spsystems.net is temporarily off the air; | Henry Spencer
mail to henry at zoo.utoronto.ca instead. |

Henry Spencer wrote:
In article ,
Geert Sassen wrote:

...As each hatch actuator finished its
stroke, the movement of the piston uncovered vent ports which released
hot gas into the igniters of the seat propulsion system.

Now that was a novel set-up!

It didn't always work in the correct sequence, i remember reading a
story about one of the seats slamming straight *through* the hatch
during a test...


They did have some debugging to do. :-) That one, if I recall correctly,
resulted from a hot-gas leak, fixed by redundant seals and more careful
quality control on some of the components. The final system was believed
reliable, but it still wasn't anything you'd use unless your life was at
stake...

Didn't John Young once remark about the chances of the seat's use
causing (paraphrasing) a very bad, but very short, headache?

--

..

"Though I could not caution all, I yet may warn a few:
Don't lend your hand to raise no flag atop no ship of fools!"

--grateful dead.
__________________________________________________ _____________
Mike Flugennock, flugennock at sinkers dot org
"Mikey'zine": dubya dubya dubya dot sinkers dot org