Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT/SPACEDIG/V15_5/V15NO594.TXT

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Date: Thu, 24 Dec 92 05:38:01
From: Space Digest maintainer <[e-mail]>
Reply-To: [e-mail]
Subject: Space Digest V15 #594
To: Space Digest Readers
Precedence: bulk


Space Digest                Thu, 24 Dec 92       Volume 15 : Issue 594

Today's Topics:
                 Aurora chase planes (was Re: Aurora)
                       AUSROC II: A Post Mortem
                          ground vs. flight
        I thinI see our problem. (Was Re: Terminal Velocity of
             The Real Justification for Space Exploration

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Date: 24 Dec 92 06:13:15 GMT
From: Mary Shafer <[e-mail]>
Subject: Aurora chase planes (was Re: Aurora)
Newsgroups: sci.space

On Wed, 23 Dec 1992 19:42:05 GMT, [e-mail] (Dillon Pyron) said:


Dillon> In article <[e-mail]>, [e-mail] (David Smith) writes:
>
>I think people are getting a little too hung up on the "chase" word.
>If I recall right, what started this was that an observer said he
>saw this unidentified plane being chased by an F-15 or F-16.  As
>an observer, how can you tell if one plane is "chasing" another or
>accompanying it?  (Mary's definition of "chase plane" is the standard
>one for testing aircraft but we're really talking about an "accompanying
>plane")  Unless there was some major manuevering going on you can't say
>that the F-15 was "chasing" or attempting to intercept with the intent
>of shooting it down or identifying an unknown plane rather than accompanying
>it as a "chase plane".

Dillon> If I saw one aircraft, armed or not, I would feel safe to assume it to be a
Dillon> "companion" plane.  If I saw two, armed to the teeth, one behind and slightly
Dillon> below, the other off center, above and further behind ... The Air Force guys I
Dillon> grew up with call that "snakes and pistols".  ie Sidewinders and guns.

Dillon> If you were to see only one "chase" aircraft, it is probably just that.  Most
Dillon> air forces (includes USN) prefer to fly in wing pairs.

Dillon> Not that I speak with any real athority.  Mary, does this seem like a plausible
Dillon> explanation (although not complete).

We do sometimes fly more than one chase.  This is usually during the
handoff from one chase to another.  An example here is the AFTI/F-111
which would go to the tanker a couple of times during a three-hour
research flight, while we sortied three chases, each good for a little
over an hour.  Why didn't we use just one chase and have it refuel,
you ask?  Because T-38s don't have refueling capability and F-18s need
a different tanker than the F-111.  (The only thing the Air Force and
the Navy agree on is that the Army shouldn't have fast jets.)

Let me agree specifically with you about armed-up airplanes--one never
chases with weapons.  It makes the research pilots nervous.  Actually,
this is because weapons are draggy.  Except for the missiles on
wingtips on the F-16 and F-18, and those will be dummies when flying
safety chase.  Remember that flight test, including the chasing, is
only done by test organizations; operational squadrons (the people who
routinely fly with weapons) are only rarely involved.  Dryden, for
example, has absolutely no weapons.  Rarely, we'll borrow some dummy
missiles if their presence is germane to a phenomenon that we wish
to observe (some sort of flow anomaly comes to mind) but we don't have
cannon.

By the way, chase should fly off to the side, usually behind and below
the research plane.  The chase has to be far enough away that it won't
interfere with the flow over the research plane, so being behind it,
in very loose formation (several spans away).  There's a classic story
floating around about some plane that had fantastic performance with
one chase pilot and average performance with all others; the one pilot
was flying too close, "pushing" the other plane with his bow wave.
(There are also stories about doing performance points in mountain
waves, but this is the wrong newsgroup for them.)  Chase pilots are
test pilots, trained in how to fly chase.  Dryden has six test pilots,
all of whom fly both research and chase flights.

I might also add that the movie "Topgun", while excellent in its way,
trades authenticity in formation flight for cinematic excitement.  The
usual battle spread that one goes into aerial combat with is up to
about a mile.  Obviously, two aircraft a mile apart are not going to
be very interesting, even on a _wide_ screen.  For this reason, the
choice was made to tighten the formation greatly, resulting in some
_great_ photo footage.  But don't be fooled, fighters don't go into
the furball in tight formation.

--
Mary Shafer  DoD #0362 KotFR NASA Dryden Flight Research Facility, Edwards, CA
[e-mail]                    Of course I don't speak for NASA
 "A MiG at your six is better than no MiG at all."  Unknown US fighter pilot

------------------------------

Date: 17 Dec 92 05:02:50 GMT
From: [e-mail]
Subject: AUSROC II: A Post Mortem
Newsgroups: sci.space,rec.models.rockets

This paper was presented by Tzu-Pei Chen at the 1992 AUSROC conference,
Adelaide, Australia, December 1992.


                  AUSROC II : A Post Mortem
                  ~~~~~~~~~~~~~~~~~~~~~~~~~
                        Tzu-Pei Chen




Abstract  -  The  AUSROC II Amateur Rocket malfunctioned  at
launch.  The LOX valve failed to open fully, preventing  the
rocket from lifting off. Pneumatic and electrical umbilicals
burnt through preventing an abort sequence. An internal fire
started in the lower valve fairing and spread throughout the
rocket, eventually destroyed the payload. A design fault  in
the  pressurisation mechanism allowed oxygen  to  enter  the
kerosene tank resulting in an explosion which destroyed  the
vehicle.  No  definite reason for the LOX valve failure  has
been  found,  but  a  seal failure in  the  LOX  valve  vane
actuator seems the most likely cause. Simple changes to both
the rocket and launcher systems could have prevented further
damage  to the vehicle after the LOX valve failure. A second
vehicle  designated AUSROC II-2 will be built  incorporating
these changes.  This paper describes what is known about the
launch  event. It proposes possible reasons for the failures
which   were  encountered,  and  suggests  solutions   where
possible.



I.  INTRODUCTION
~~~~~~~~~~~~~~~~
     "If  one part fails the whole thing can fail. It's
     not  like a car, if you get a flat tire, you  stop
     and  put  another one on ... if you blow a  valve,
     you'll  probably blow up your tanks and everything
     along with it."
                                  Mark Blair, March '92

On October 22nd 1992 at about 10:15am an attempt was made to
launch   the  AUSROC  II  Amateur  Rocket  at  the   Woomera
Instrumented Range. A series of malfunctions occurred  which
resulted in a failure to launch, and subsequently led to  an
explosion and total destruction of the vehicle.

At  7:00am the 3 hour Flight Firing Sequence commenced.  The
helium  pressure  bottle was pressurised to  20MPa  and  the
launcher elevated. The kerosene tank was then filled.  A dry
nitrogen  supply was connected to the LOX tank and  the  LOX
valve  opened. The LOX system was then purged for 5  minutes
to  remove  any moisture from the LOX feed system especially
the  LOX  ball valve. The lower valve fairing was  inspected
visually for any signs of kerosene leakage, and then sealed.
At  T-30'00",  LOX fuelling commenced, and was  completed  8
minutes  later.  It  was observed that only  a  light  frost
formed  on the tank walls when full. At this point  kerosene
was  discovered to be dripping from the base of the  rocket.
The  amount of leakage was assessed to be insignificant, and
a decision to continue with the launch was made.

At  T-15'00"  the  Final Arm & Launch  Sequence  began.  The
ignition  circuit  was  connected  and  all  personnel  were
cleared  from the launcher. At T-2'00" the automatic  launch
sequence  was initiated. Forty seconds later at  T-1'20"  an
ABORT  was  called. The picture from the onboard camera  had
suddenly  deteriorated. The countdown  was  held  while  the
problem was discussed, 10 minutes later the automatic launch
sequence was restarted at the T-2'00" mark.

At  T-5s,  the electric match fired, and the ignition  flare
ignited  successfully.  At  T-3s  the  helium  valve  opened
pressurising both propellant tanks. At T-0.25s the  kerosene
valve  opened (as the kerosene takes about 250ms  to  travel
through  the regenerative cooling passage of the motor).  At
T=0s  the LOX valve was actuated, but failed to open  fully,
resulting  in  insufficient thrust to lift the  vehicle.  An
attempt  to  abort  the launch was made  at  T+2s,  but  the
massive  kerosene  plume  had burnt  through  nearby  ground
pneumatic lines preventing the abort system from closing the
propellant  valves. At the same time a crackling or  popping
sound could be heard. Eventually, at around T+10s, the  more
characteristic  "thrusting" sound developed  and  the  plume
became much brighter indicating that some oxygen was present
in  the  chamber.  Kerosene continued to be  expelled  under
pressure  until  T+15s.  At  around  T+20s  the  electronics
umbilical  was also destroyed preventing switch off  of  the
payload.  With the payload control lines cut, the  payload's
timer, thinking the rocket had left the launcher, started  a
55s countdown to deploy the recovery mechanism.

A  small fire could be seen at the bottom of the motor,  the
remaining   kerosene  dribbling  from  the  rocket   burning
brightly  in oxygen. Kerosene on the ground and  around  the
launcher  also  continued to burn with a much redder  flame.
>From  the  onboard camera, smoke could now be seen streaming
from  the upper valve fairing. At T+1'16" the payload  fired
the  nose  separation pins, and then the nose  push  rod,  2
seconds  later. The nose cone popped off to  one  side,  and
fell  to the ground. At T+1'25" the payload failed, and  all
telemetry  except  for the video was lost.  At  T+1'40"  the
video transmitter stopped.

The  flame  at  the  bottom of the motor continued  to  burn
brightly. The fire around the launcher eventually  went  out
about  1 minute later. At T+3'45" a mixture of kerosene  and
oxygen  exploded in the kerosene tank, rupturing  the  tanks
cable  duct.  The expanding gases tore out  both  the  lower
valve,  and intertank fairing hatches, and then sheared  the
bolts fixing the intertank fairing to the LOX tank. The  LOX
feed  line was severed at the LOX tank boss, and the  rocket
was blown in half. The remaining LOX pressure was sufficient
to  lift  the top half of the rocket off the launcher  rail,
and  propel it through the air and then along the ground for
some tens of metres.

After  a 30 minute cool-off time and careful examination  of
the  wreckage  from  the periscope in  EC2,  the  operations
manager  and range safety officer proceeded to the  launcher
area to make the area safe. Mains power was removed from the
area,  and the pyrotechnic cutters associated with the  main
parachute were disarmed. The various pieces of wreckage were
gathered  together  and brought back  to  Test  Shop  1  for
examination.

The  upper  portion of the rocket was severely  dented,  and
disassembly  was  not  possible on  the  day.  Most  of  the
fittings  in  the  lower valve and intertank  fairings  were
either  missing or very badly burnt. The engine however  was
removable  and  it  was discovered that the  LOX  valve  had
indeed opened by about 10 degrees.

The  immediate conclusion, reported by most of the media  on
the  day,  was that the LOX valve had frozen shut,  possibly
due  to  the  extended countdown. Eventually it was  decided
that  this was unlikely considering the low humidity on  the
day  and  the  fact that the dry nitrogen purge should  have
left  nothing to freeze within the LOX valve. The  preferred
explanation  was  that one of the pneumatic lines,  probably
already burning due to the kerosene leak, had burnt through,
just as the LOX valve was opening [1].

The remains of the rocket were shipped back to Salisbury  to
be  fully dismantled. The motor, and the remains of plumbing
from  the lower valve fairing were brought back to Melbourne
for inspection.


II.  FAILURE ANALYSIS
~~~~~~~~~~~~~~~~~~~~~
     "The  price  one pays for pursuing any profession,
     or  calling, is an intimate knowledge of its  ugly
     side."
                                          James Baldwin

As described above, there were in fact several malfunctions,
some  of  these  prevented the launch of  the  rocket,  some
contributed to the subsequent destruction of the rocket, and
some were simply embarrassing. The major failures which will
be discussed are;

 - sudden deterioration of the onboard camera picture,
 - the LOX valve failing to open,
 - kerosene seen dripping from the base of the rocket,
 - the internal fire
 - the explosion in the kerosene tank,
 - failure  of  the abort sequence to close the  propellant
   valves, or disable the payload,
 - lack  of  concrete  data  with  which  to  analysis  the
   failure.


A.  Onboard Camera Picture Failure

The  sudden deterioration of the video picture took the form
of   saturated  white horizontal bars forming  about  bright
portions of the picture. During the launch, these bars  were
present to an extent, but not enough to really detract  from
the  overall picture. However at the exact time the  payload
was  switched to internal power, these bars suddenly swamped
around  30% of the picture. Causing the telemetry  personnel
to call a hold.

The horizontal bars were caused by solid state regulators in
the  actual  camera shutting down (thermal  limiting)  after
overheating. The camera had been connected directly  to  the
rocket's unregulated power supply which is nominally 14V,  a
little higher than the camera's nominal operating voltage of
12V.   The  condition  became  drastically  worse  when  the
payload  was switched to internal power because the  lithium
battery  pack  used  to power the payload,  was  capable  of
supplying,  initially,  around 17V.   The  same  effect  was
repeated in Melbourne, after fire damage to camera had  been
repaired.  The camera was connect to a 14V power supply  and
allowed  to operate for some time (around 20 minutes)  until
the  horizontal white bars developed, then the power  supply
was raised to 16V, and a very similar effect was observed.

The  fault  could  have been avoided  had  the  camera  been
connected  to  a  regulated power  source.  In  fact  a  12V
regulator was provided for the camera on the rocket's  power
supply, but this output had simply not been used.


B.  LOX Valve Failure

The  most  obvious  and vexing question of  course,  is  the
reason  for the LOX valve failure. The original explanation,
that a pneumatic line had burnt through at exactly the right
moment  seemed a little unlikely. At the last static firing,
valve  position sensors showed that the time taken  for  the
LOX  valve to opens is in the order of around 60ms  [2],  so
for  the  LOX  valve  actuator to have  moved  11%  requires
failure within a window milliseconds wide, an unlikely event
indeed.  Thus a reason which inherently moves  the  valve  a
small  amount  would be infinitely preferable to  one  which
relies   on   split-second   bad  luck.   Possible   reasons
investigated included;

a) an electrical failure due to ;
    - an umbilical being disconnected,
    - an   electronic   failure  in  the  Launch   Sequence
      Controller (LSC) or it's power supply.
b) a pneumatic failure due to;
    - a  loss  of pressure to the actuators due to a breach
      in  the ON side pneumatics, a 1MPa regulator failure,
      or   a   pneumatic  (Legris  push  fitting)   fitting
      failure,
    - an  electrical  or  physical  failure  in  the  pilot
      solenoid,
    - a failure in the vane actuator.
c) mechanical failure due to;
    - the  valve seizing due to mechanical distortion  from
      cryogenic temperatures,
    - the  ball  freezing to the valve seat due to moisture
      being present,
    - the  valve  stem or perhaps valve sensors jammed  due
      to ice build up,

The  majority  of  these possibilities were rejected  simply
because  they  did  not  satisfy  the  split-second   timing
problem.

An  electrical failure was discounted as the LSC's indicator
lights  showed that appropriate signals were being  sent  to
the  pilot  solenoid valves. The LSC was  tested  later  and
proved to be fully functional.

An  ON  side pneumatic line failure was seriously considered
as  a  possibility.  The kerosene leak in  the  lower  valve
fairing  would  have  dribbled kerosene onto  the  pneumatic
lines  leading to the rocket. These lines would have ignited
with  the  flare, severely weakening them. Conceivably  then
the  kerosene plume exiting from the motor could have  burnt
through  the lines then, as the timing was chosen such  that
the  kerosene  and LOX exit almost simultaneously.   However
high   speed  film  shows  no  sign  of  the  lines  burning
beforehand, and the kerosene plume does not exit the  rocket
motor  for  about  0.5s.  It was  also  suggested  that  the
kerosene  leak may have lubricated one of numerous pneumatic
couplings  allowing a line to blow off. This was  discounted
by  collecting  all the push-fittings and  checking  that  a
piece of tubing was still firmly inside the fitting.

A failure with the pilot solenoid was rejected mainly due to
the  timing  reasons mentioned. Unfortunately, the  solenoid
was  very badly damaged making it difficult to prove  beyond
doubt that it was operational.

Originally  the vane actuator was not even considered  as  a
possible  point of failure. However it was mounted  directly
onto  the  LOX  ball valve, and its mechanism  contains  two
seals which may not operate properly beyond around -20C. Had
these  seals failed, the expected response would match those
observed very well. Thus a seal failure in the vane actuator
is  a  preferable  explanation, and is discussed  in  detail
below.

The actual LOX ball valve seizing from mechanical distortion
was rejected out of hand as the valve is explicitly designed
to  handle cryogenic fluids. Freezing of the valve stem,  or
the position sensor was rejected due to the lack of humidity
on  the day. Even had a layer of ice formed, it is unlikely,
given the small surface area, that it would have jammed  the
vane  actuator.  In  light  of the  kerosene  leak,  it  was
suggested that the whole mechanism may have been frozen in a
lump of kerosene ice. However if this was the case, than the
valve would not have opened at all.

At an earlier static firing (14/3/92) the LOX valve had also
failed  to  open  fully. Inspection of the valve  afterwards
showed  that there was trichloroethane present  in  the  LOX
valve itself, a remanent from an earlier procedure to remove
grease  from  the  LOX feed system. This  event  caused  the
addition  of  a  dry nitrogen purge to the launch  sequence.
Nitrogen  is flushed through the LOX feed system,  hopefully
removing  any residual solvents as well as any water  vapour
present  in  the  tank. This procedure would  appear  to  be
successful as the following 3 static firings progressed with
out  a  hitch. For this reason, as a dry nitrogen purge  was
performed, this theory was discarded.

The  vane  actuator was used to actually turn the  LOX  ball
valve.  It  was mounted directly to the body by an aluminium
mount, and coupled to the valve stem via a slip on coupling.
The  aluminium block was machined to contact well with  both
the  valve  body, and the bottom of the vane actuator.  This
mount  would have formed a reasonable thermal path from  the
body  of  the  valve to the body of the vane  actuator.  The
seals  within  the vane actuator are made from  polyurethane
and  have a nominal working temperature range which  extends
as  low as -20C. Beyond this temperature, the seals begin to
lose their elasticity. LOX was present at the LOX ball valve
for  40 minutes (30 minutes from the start of fuelling, plus
another  10  minutes  for  the  hold).  With  LOX  having  a
temperature  of  around 90K, in the enclosed environment  of
the  lower valve fairing, it is entirely possible  that  the
vane  actuators  body  temperature  could  have  fallen   to
unacceptably low temperatures.

If  this was the case, then the vane would have "frozen"  in
the   closed  position.  When  the  pneumatic  pressure  was
applied,  the  vane  would  have hesitated  and  then  moved
possibly in "stutters". With the seal no longer plastic, the
gas  may  also  have  burst under  the  seals  delaying  the
movement  even  further. With the LOX valve partially  open,
the  plume cuts through the pneumatic lines, while the  vane
actuator is still stuttering open, some seconds later.  This
would seem to be the most plausible reason for the LOX valve
failure.  Hopefully  a test can be conducted  utilising  the
Helium  valve vane actuator (if it has survived) to  confirm
this. If this is the case, the abort may have contributed to
the  failure,  as  it  added 10 minutes  to  the  countdown,
extending the time LOX was present at the valve by 33%.


C.  Kerosene Leak

A  leak in one of the kerosene valve's body connector  seals
was  detected  during final pressure tests  the  day  before
launch. As it was a gas leakage at a negligible rate, it was
decided  to  ignore  it. On the launch day,  after  kerosene
fuelling, it was observed that no kerosene was leaking  from
the body connector seal. However after the LOX fuelling, and
the  sealing  of the LOX bleed plug, it was discovered  that
kerosene was leaking from the bottom of the rocket [1].

The  leak  in the seal itself was caused simply because  the
type of body connector seals used in the kerosene valve were
in fact once-only seals, that is they deform to form a seal,
but  once the valve is disassembled they stay deformed,  and
should  be  discarded. This was not the case, the seals  had
been  used  four or five times already. The leak  manifested
itself only after the LOX tank had been sealed because of  a
design fault in the tank pressurising system.

The  LOX tank is self pressurising in the sense that the LOX
is constantly boiling off, so that the pressure rises in the
tank  once  it is sealed. The tank pressurising  system  was
designed  assuming that the tank regulators acted  as  check
valves and thus would prevent backflow from a pressurised to
tank  back  into the system [3]. This proved not to  be  the
case. Once the LOX tank was filled, a small amount of oxygen
under  its own pressure flowed back through the pressurising
system  and  into  the kerosene tank. The amount  of  oxygen
would  have been very small, however this pressurisation  of
the kerosene tank was enough to cause the kerosene to leak.

The  kerosene  leak in itself was probably not  as  major  a
problem  as  it  sounds.  However  by  dribbling  down   the
umbilical,  it  supplied a path by which the  exhaust  plume
could ignite the wiring loom inside the lower valve fairing.


D. Fire Inside the Rocket

A  fire inside the lower valve fairing should not have  been
as  major a problem as it was. A tiny volume, mostly  sealed
at the top, a fire should have quickly suffocated itself. In
addition  the  insulation  on  the  wiring  loom  was  self-
extinguishing,  that  is  if  lit  by  a  open  flame,   the
insulation does not continue to burn in air once  the  flame
is removed.

As was mentioned earlier, the LOX tank self pressurises. For
this  reason a relief valve is placed at the top of the  LOX
tank,  and set to crack at 4.5MPa. The vent from this relief
valve  was not piped to the atmosphere, but left within  the
rocket.  During the countdown, the LOX tank would have  been
slowly  venting into the rocket body, and venting  furiously
during  the 15 seconds after T=0s (as can be seen  from  the
onboard camera). This would have provided a very oxygen rich
atmosphere within the rocket, allowing the looms to burn  up
the  rocket as far as the payload, eventually destroying it.
The  amounts of oxygen present can be seen from  the  severe
"weathering" of all the aluminium parts after the fire.


E.  Kerosene Tank Explosion

As mentioned earlier, oxygen was able to bleed back, through
the  LOX regulator, from the LOX tank to the kerosene  tank.
After  all  the kerosene had been expelled, and  the  helium
pressurising  gas  vented,  oxygen  bled  back  through  the
pressurising  system to forming  a fuel air  mixture  within
the  kerosene  tank. When the mixture ratio  was  right,  it
ignited from the small kerosene fire seen at the at the base
of  the  motor. The flame travelled back through the motor's
cooling passages, and through the injector into the kerosene
tank.  The  residual  kerosene may even  have  been  burning
inside the kerosene tank for a while before exploding.

The explosion ruptured the LOX pipe conduit, at its weld  to
the  top  of  the  kerosene tank boss. The hot  gasses  then
expanding  down through the LOX pipe conduit into the  lower
valve fairing. The lower valve fairing hatch's backing plate
was  buckled and then blown from the rocket, coming to  rest
on the launch apron ring road. The upper valve fairing hatch
was  likewise torn out. Some gas rushed upwards through  the
pressure line & wiring conduit into the electronics fairing,
breaching  the camera's case and pushing the main  parachute
out  of  it's tube. The bolts holding the intertank  to  the
bottom  of  the  LOX  tank boss then sheared,  breaking  the
rocket  it  two. The upper launch lug broke, and the  rocket
was  thrown to one side. The LOX feed line ripped from  it's
fitting at the base of the LOX tank, and the thrust produced
by  the  LOX being expelled was sufficient to lift  the  top
half  of  the  rocket, through the air and  then  along  the
ground for some distance. The bottom half of the rocket  was
also  torn from the launcher, and fell to the ground nearby,
the   remaining  kerosene  visibly  burning  for  a  several
seconds.

The  bleed  back through the regulator was more  complicated
than just simple two-way flow through the regulator. It  can
be  shown that had the LOX valve completely failed to  open,
then  the  events leading to the explosion could  have  been
avoided (see Appendix A).


F.  Abort Sequence

Originally the rocket was designed with no abort  system  at
all,  however  at the static firings it was discovered  that
the  existing pneumatics could, with the addition of  a  few
lines,  allow the propellant valves to be closed as well  as
opened. This system used at each of the static firings,  and
then  incorporated  into the rocket itself,  if  only  as  a
convenient method of shutting the valves during tests.

The  abort system was actuated at about T+2s, but was unable
to  close  the propellant valves because the pneumatic  line
used  to close the valves had already burnt through  in  the
exhaust plume of the rocket. Likewise the payload could  not
be  disabled  because the electrical umbilicals  also  burnt
through.  The  failure  of  the abort  system  is  the  most
unacceptable  of  all  the failures  as  it  was  thoroughly
predictable, and easily avoidable.


G. Lack of Data

Most  of the analysis involved a large degree of speculation
because little data of the failure was available. All of the
cameras were placed to take rather optimistic "long"  shots.
So  no clear picture of the base of the rocket is available.
This  was  compounded with problems with the  payload  which
resulted  in  critical data such as the tank pressures,  and
the valve position sensors being lost.



III.  SOLUTIONS
~~~~~~~~~~~~~~~
     "For every problem there is one solution which  is
     simple, neat, and wrong."
                                          H. L. Mencken

With  "20/20:  hindsight,  it  is  easy  to  propose  simple
solutions  to  many  of  the  problems  which  have  already
occurred. The real solution is to actively try and find  all
the  possible  failures  have not  occurred  and  to  either
prevent  them or at least have procedures as to what  action
to take, when they occurred. As a case in point, the payload
could  have been disabled in the first 20 seconds after  the
failure,  as  the  electrical  lines  where  still   intact.
Although  this would not have saved the rocket, at least  it
would have prevented some media embarrassment.

The  abort  system and payload umbilicals should  have  been
heavily   protected  from  the  exhaust  plume.  An   E-flux
deflector  could be welded to the base of the launcher.  The
pneumatic  lines  running to the rocket, as  well  as  those
inside  should be replaced by stainless or aluminium tubing.
The  1MPa pneumatic supply should be moved much further away
from  launcher, and protected. The electric umbilicals could
be  connected high up on the rocket so as to be out of harms
way.  The  close valve could be placed inside the rocket  so
that there is only one pneumatic line leading to the ground.

Check  valves should be installed after the each  propellant
tank  regulator in order to prevent the bleed back of gases.
Both   the   LOX  and  kerosene  relief  valves  should   be
repositioned  so that they vent to the atmosphere,  not  the
inside of the rocket.

All  components  used should be carefully  studied  so  that
items  such  as non-reusable seals are replaced, and  normal
operating conditions are not exceeded. The current LOX valve
arrangement  could be used with the addition  of  a  thermal
insulator  such  as a plastic or ceramic plate  between  the
body  of  the  vane  actuator, and  the  valve  body  mount.
Extensive  testing  of each of the possible  valve  failures
should  be  investigated under realistic  conditions  (using
liquid nitrogen) and worst case data should be obtained.

An  automatic abort sequence could be added to  the  LSC  in
order   to  cut  down  response  time  assuming  appropriate
telemetry  data  is available. Better displays  of  realtime
engineering  data  would also allow better decision  making.
Finally,  more  formal  procedures, especially  launch/abort
criterion  need to be established beforehand so  that  these
decisions are not made "in the heat of the moment".



IV.  CONCLUSION
~~~~~~~~~~~~~~~
     "You may be disappointed if you fail, but you  are
     doomed if you don't try."
                                         Beverley Sills

AUSROC II failed to lift off because the LOX valve failed to
open  fully. The most likely explanation is that  the  valve
only  partially  opened  because the  seal  inside  the  LOX
valve's  vane actuator failed due to prolonged  exposure  to
low temperatures. The sudden deterioration in the live video
signal  was  due  to incorrect wiring of the video  camera's
power  supply.  The  10  minute hold caused  be  the  camera
problem may have contributed to the LOX valve failure. After
the  LOX  valve  had  failed to open, it  should  have  been
possible to save AUSROC II by closing the propellant valves,

and  disabling the payload. This was not done, as the  wires
and  pneumatic lines associated with the abort system,  were
not  protected in any way, and therefore burnt through in  a
matter  of  seconds. Simply shielding the  wires  and  using
stainless  steel  pneumatic lines would  have  avoided  this
problem. An automatic abort sequence based on telemetry data
would  allow  the launch to be aborted the instant  a  valve
failure is detected.

The  explosion  which destroyed the vehicle  was  caused  by
oxygen flowing backwards under its own pressure, through the
LOX  regulator  into  the kerosene tank.  Residual  kerosene
vapour in the kerosene tank mixed with the oxygen to form an
explosive  mixture. The backflow occurred due  to  a  design
fault  in  the  pressurising system, a  check  valve  placed
before or after the LOX regulator would prevent the problem.

The  kerosene leak was caused by a non-reusable  seal  being
reused  in  the kerosene ball valve. This leak  provided  an
ignition source for the fire inside the rocket, and while it
contributed  to the destruction of the payload, it  probably
did not contribute otherwise to the launch failure. Although
the  wiring looms were self-extinguishing, the placement  of
the  LOX  relief valve vent inside the upper  valve  fairing
provided  an oxygen rich atmosphere within which they  could
burn.  The  relief valve should be placed so that  it  vents
directly to the atmosphere.

If   AUSROC  Projects  is  to  continue  another  AUSROC  II
(designated  AUSROC  II-2) vehicle needs  to  be  built.  An
opportunity  now exists to incorporate all  of  the  changes
which  had been suggested during the construction of  AUSROC
II-1, as well as the changes suggested here.

The  design  of  AUSROC II was in many ways too  "positive".
Much  thought  had  been put into each of the  systems,  but
little  thought had been allocated to possible failures  and
their  consequences.  Obviously,  greater  testing  of  each
component may have shown up some of these problems  earlier.
This simply highlights the very limited resources with which
the  group currently works. The six static firings  were  in
themselves,  major  system tests, but they  were  already  a
major strain on our resources. Hopefully AUSROC II-2 will be
able  to proceed in an environment where financial and  man-
hour   constraints  become  secondary  to  the  process   of
engineering.


References

[1]AUSROC  Projects,  AUSROC II Launch Campaign  Review,  26
   October 1992
[2]A. Cheers, Static Firing Data - 25/4/92 1st Firing, April
   1992
[3]M. Blair and P. Kantzos, Design of a Bi-Propellant Liquid
   Fuelled   Rocket,  Final  Year  Project   Thesis,   Dept.
   Mechanical Engineering, Monash University, 1989


Author

Tzu-Pei Chen             Phone:    [phone]ah
Ardebil Pty Ltd          FAX:      [phone]
6 Kooringa Crescent      Pager:    [phone]
Mulgrave  VIC  3170      Email:    [e-mail]


Previous AUSROC updates can be obtained by anonymous ftp to
audrey.levels.unisa.edu.au in directory space/AUSROC

--
Steven S. Pietrobon,  Australian Space Centre for Signal Processing
Signal Processing Research Institute, University of South Australia
The Levels, SA 5095, Australia.      [e-mail]

------------------------------

Date: Thu, 24 Dec 1992 06:05:43 GMT
From: Henry Spencer <[e-mail]>
Subject: ground vs. flight
Newsgroups: sci.space

In article <=[e-mail]> [e-mail] (Greg Moore) writes:
>>>    ... What did Michael Collins do while on the Agena?
>>Apart from just generally evaluating how easy it was to do -- not very --
>>he retrieved a micrometeorite experiment package...
>>
>    Actually Henry, that supports my original point, that EVA to and
>on and unstabilized platform isn't easy.

The platform being unstabilized actually had little to do with it, aside
from dictating a relatively early end to the exercise when Collins's
various forces exerted on it started complicating its motion to the
point of unpredictability.  The problems were general issues of EVA,
not particular to the nature of the Agena.  NASA hadn't fully realized
the difficulties of free-fall maneuvering in spacesuits at the time.

>    However, I do find that this was sone very interesting.  Any
>idea how much if any tumbling the Agena was doing?

It was pretty steady when the exercise started, but the situation did
deteriorate.

>>[shuttle arm]
>>It's not rated for the full mass of an orbiter, which is why the station
>>arm will eventually take over the capture-for-docking job.
>>
>    I meant to ask about this earlier.  I thought at one point I
>saw a diagram for a special "arm" to do this...

I don't recall seeing anything like that, and I'm fairly sure it's not
planned now.  It may well have been proposed.

>    Also, given that the bottom of the shuttle is covered with
>tile, can the orbiter exert a Y+ (i.e. vertically up) translation?

There aren't any RCS nozzles on the orbiter's belly, but both the forward
and aft RCS systems have nozzles angled down so that they can (somewhat
inefficiently) thrust upward.

>>As far as I know, the success rate for grapple fixtures is 100%.  They've
>>sometimes had to proceed slowly and carefully, but I don't think they've
>>ever had to abandon a grabbing attempt.
>
>    Didn't they ahve to manually slow down a rotating satellite
>since the arm couldn't grapple the fixture fast enough? (Solar Max?)

On Solar Max, originally Pinky Nelson's backpack was to take the spin
off the satellite so it could be grabbed by the arm.  Didn't work because
the fancy grappling gadget he was equipped with -- unrelated to the one
on the arm -- didn't work.  He did try to do it manually, but that wasn't
properly planned and it didn't work either.  Nobody really expected a
direct grapple attempt with the arm to work, although they did try it.
Eventually they decided to gamble, slowed the spin down a lot with the
satellite's on-board systems, and *then* the arm got it.

On the Palapa/Westar retrieval, the next generation of fancy gadgets didn't
work either, but that time they had a manual backup plan, which was used.
(Like Intelsat, these birds had no grapple fixtures, so the arm couldn't
be used until *something* was grappled to them by other means.)  On the
Leasat repair, the hardware was kept very simple and the astronauts'
arms did almost all the work.  (How quickly they forgot these lessons...)
--
"God willing... we shall return."       | Henry Spencer @ U of Toronto Zoology
       -Gene Cernan, the Moon, Dec 1972 |  [e-mail]  utzoo!henry

------------------------------

Date: 24 Dec 92 06:08:02 GMT
From: Henry Spencer <[e-mail]>
Subject: I thinI see our problem. (Was Re: Terminal Velocity of
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (Brian Stuart Thorn) writes:
>>Do you have any idea how many DC-3s are still flying?  After 50
>>years?
>
>        How many Mercury or Vostok are still flying?

Vostok-derived unmanned return capsules *are* still flying.  (And apart
from modest changes in upper stages, the boosters that launch them --
also Soyuz, Progress, etc etc etc -- are the same type that launched
Sputnik.)
--
"God willing... we shall return."       | Henry Spencer @ U of Toronto Zoology
       -Gene Cernan, the Moon, Dec 1972 |  [e-mail]  utzoo!henry

------------------------------

Date: 24 Dec 92 09:26:02 GMT
From: Brian Yamauchi <[e-mail]>
Subject: The Real Justification for Space Exploration
Newsgroups: sci.space,talk.politics.space

In article <[e-mail]> [e-mail] (Ken Arromdee) writes:
>In article <[e-mail]> [e-mail] (David Toland) writes:

No, he didn't.  I did.

>>It seems to me that all of these spinoff arguments, Malthusian
>>arguments, and "dinosaur killer" arguments miss the point.
>>Asking "why explore space?" is like asking "why feed the starving?",
>>"why create art?", or "why do basic science?"  It all comes down to
>>basic human drives, and I would argue that the drive to explore is
>>just as basic as the drive to help, to create, or to learn.

>I would argue that there are a lot of other things that are basic human drives,
>some a lot less benign.  (You can name your own examples.)

>We humans have the capability to decide to override our instincts when we can
>figure out that following them is not good for us.  To claim that exploration
>is a basic drive is not a justification--if anything, it reduces space
>exploration to the human equivalent of lemmings running over a cliff.

Are you arguing that all non-survival related drives should be
suppressed?  Or only the ones which are actively harmful?

If you're arguing the latter, then I fail to see how space exploration
falls into the same category as jumping off a cliff.  Just because a
drive isn't necessary for survival doesn't mean that it's suicidal.

Is the drive to care for one's offspring (even at great personal cost)
also equivalent to being a lemming?

>>When Sir Edmund Hillary was asked why he climbed Everest, he answered,
>>"Because it's there."  The same answer is just as appropriate for why
>>we explore space -- because the entire universe is out there...

>If you must succumb to your animal instincts, go ahead.  I suggest not using
>public money, taxed from me whether I want to support your instincts or not.

Fair enough -- the same, of course, should apply to those who don't
want their money going to the poor, or to defense, or foreign aid, or
farm subsidies, or any of the other myriad of government programs...

Are you an anarchocapitalist?  If so, then fine -- you have a
consistent position against coercive funding of anything.  Otherwise,
how is space exploration different from any of the other government
programs which have less than universal popular support?

If we eliminated taxation altogether, then those of us who support
space exploration would have a lot more of our own money to
voluntarily spend on such projects.  For better or worse, that's not
likely to happen in the near future.

That having been said, I would like to point out that I said nothing
about government funding of space exploration in my previous post.
The more I see about how government works, the more convinced I become
that space exploration and development needs to be done by the private
sector if it is going to be done at all.

At best, government can fund some of the basic research in space
science and technology and some of the high-risk exploratory
development in advanced technologies.  At worst, we get huge
bureaucracies which are primarily motivated by a desire for larger
budgets rather than any real commitment to exploration.

Ideally, I would like to see all exploration funded either through
private corporations or non-profit organizations.  To get from here to
there, we first need to get the cost of spacecraft down to the point
where these organizations can afford such ventures.  I think SSTO is a
major step in the right direction -- so is Pegasus, so would be some
of Truax's designs if he ever gets them built...
--
_______________________________________________________________________________

Brian Yamauchi            Case Western Reserve University
[e-mail]    Department of Computer Engineering and Science
_______________________________________________________________________________

------------------------------

End of Space Digest Volume 15 : Issue 594
------------------------------