[Date Prev][Date Next][Thread Prev][Thread Next] - [Date Index][Thread Index][Author Index]

Correction: Analysis of AO-40 Telemetry From Bipropellant Engine Burn Attempts



See CORRECTION below.
   Analysis of AO-40 Telemetry From Bipropellant Engine Burn Attempts

The AO-40 spacecraft carries two thruster engines, a liquid fueled
bipropellant engine,
and ammonia "fueled" electrically powered arc-jet thruster.  The
bipropellant engine
was first used on December 11, 2000 UTC to boost the orbital apogee
height.

On the first attempt at about 04:14:27 UTC telemetry indicated valves
opening and
closing but no changes indicating any other changes.  After the first
attempt reports
from command stations indicated stuck valves prevented the burn.

On the second attempt (one orbit later) at about 16:03:59 UTC telemetry
indicated
valves opening and pressure and temperature changes showing the burn in
progress.
The helium tank high pressure dropped from 182 to 170 Bar, the
low-pressure helium
rises from 0 to 15.6 Bar. Also the helium tank pressure may have cooled
from
10.7 to 8.1 C.  (This may also be due to 'stirring' of tank contents
caused by
acceleration.) Later indications from communications changes, and
command stations
showed that the engine did thrust.  However, command stations indicated
that the
thrust period was about three minutes [originally I incorrectly stated
seconds]
longer than expected.      **** CORRECTION ****

Telemetry data:

First Burn (unsuccessful)
Date: 2000/Dec/11 UTC
EVENT|TIME UTC| MA| LIU|INSTR|HIPRES|LOPRES|VALVE|MMH-3|N2O4+|N2O4-|HE
NUMB.|        |   | Pwr|  Pwr|   Bar|   Bar|
|TempC|TempC|TempC|TempC
 #A  |04:14:27|255| ON |  ON |   196|   0.0|close| 10.0|  9.4| 10.7|
10.0
 #B  |04:14:40|255| ON |  ON |   196|   0.1| OPEN| 10.0|  9.4| 10.7|
10.0
 #C  |04:17:27|  0| ON |  ON |   196|   0.1| OPEN| 10.0|  8.7| 10.7|
10.0
 #D  |04:17:50|  0| ON |  ON |   196|   0.0|close| 10.0|  8.7| 10.7|
10.0
 #E  |04:19:50|  0| off|  ON |   196|  -0.1|close| 10.0|  8.7| 10.0|
10.0

Second Burn (Successful)
Date: 2000/Dec/11 UTC
EVENT|TIME UTC| MA| LIU|INSTR|HIPRES|LOPRES|VALVE|MMH-3|N2O4+|N2O4-|HE
NUMB.|        |   | Pwr|  Pwr|   Bar|   Bar|
|TempC|TempC|TempC|TempC
 #F  |16:03:59|255| ON |  ON |   182|  15.2|close| 11.4| 10.7| 11.4|
10.7
 #10 |16:04:13|255| ON |  ON |   182|  15.6| OPEN| 11.4| 10.7| 11.4|
10.7
 #11 |16:06:59|  0| ON |  ON |   173|  10.1| OPEN|  9.4| 10.0| 11.4|
9.4
 #12 |16:07:22|  0| ON |  ON |   170|   9.8|close|  9.4| 10.0| 11.4|
9.4
 #13 |16:08:52|  0| off|  ON |   170|   7.7|close|  9.4| 10.0| 11.4|
8.1

Please note that the above telemetry data was contained in transmitted
by AO-40 until
transmissions ceased at 2000/Dec/13 11:22:31 UTC.

I am unable to explain the Helium high pressure drop (from 196 to 182
Bar)
between the First and second 'burns'.  Notice that between the burns the
drop
is 14 Bar and during the second burn it is 12 Bar.

Abbreviations:
# Hexidecimal number
MA Mean Anomaly (0-255)
LIU Liquid Ignition Unit (Electronic controls for the 400N engine)
INSTR LIU & EPU Instrumentation
HIPRES Helium pressure in Bar
LOPRES Helium pressure in Bar
VALVE OPEN / CLOSED
MMH-3 Mono-methyl hydrazine
N204 Nitrogen tetroxide
HE Helium gas

I hope this information is interesting to others.  Lets all hope that
all
is well and communications can be restored some time this millenium!

Thu, Dec. 21, 2000 01:30:12 UTC
by: Richard D. Burgan, WC8J
73's


----
Via the amsat-bb mailing list at AMSAT.ORG courtesy of AMSAT-NA.
To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org



AMSAT Top AMSAT Home