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NASA's HETE Coming Down
terrymr writes "NASA expects the High Energy Transient Experiment spacecraft which failed to successfully detach from the third stage of its launch rocket in 1996 to fall to earth within the next few days. While most of the spacecraft will likely burn up in the upper atmosphere there is a good chance that the spacecraft's batteries (weighing 33lbs each) may reach the ground intact. Current predictions put re-entry at 4:41 EDT Sunday April 7 (+/- two days)."
Do you remember math?
In other words, the weight of all 4 batteries is 15 kilos, not the weight of each battery. Still, 3.5 kilos at terminal velocity is nothing to sneeze at - perhaps I should buy a large number of pillows from Yahoo!....
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As far as I know, in recent years, ie the 90s, NASA has only used plutonium decay reactors for missions that go past mars, where solar panels are ineffective. Also, if memory serves, the launching of nuclear reactors is forbidden on the global level these days...... Thats why when NASA has been dumping lots of money into things like impulse drive as of recent.
Umm... why was this modded up? This is just plain ridiculous, and the person posting has no idea what he/she is talking about. NASA only puts nuclear power cells on probes that are headed to deep space, where the light from the sun is too weak to use solar power. No NASA satellite in orbit around the earth uses nuclear power, period. It is just too big of a hassle compared to the ease of solar panels and batteries.
And again, the reason that the prediction is vague is because the satellite is reentering the atmosphere at a very shallow angle. This makes it impossible to accurately predict when, and therefore where, the satellite will reenter.
try http://liftoff.msfc.nasa.gov/RealTime/JTrack/3D/JT rack3D.html and select SAC-B/HTET/PEGASUS under satelites.
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Um, you might want to actually read about the satellite before assuming it uses radiothermal generators.
The great big solar panels in the picture of the satellite might have been a hint that it didn't use nuclear power.
From the HETE pages (describing HETE-2, an exact duplicate of the HETE-1 craft whose launch was unsuccessful):
The HETE-2 power system hardware consists of
You can find more information on the specs of the HETE satellites at http://space.mit.edu/HETE/spacecraft.html .
By comparison, figuring out when an asteroid will hit the earth is a simple matter of determining it's path and speed and doing a simple calculation.
People keep asking why they don't know when it will hit"
"The re-entry is uncontrolled, and due to potential solar flux variations, time and location predictions will not be reliable until only a few hours before the re-entry event," said Scott Hull"
And contrary to what the original post says, the batteries are not 33 pounds each. That is the total weight of all of them.
Initial analysis indicates that only four small stainless-steel batteries, weighing a total of 15 kilograms (33 pounds) will survive re-entry."