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Am writing a story which involves a person coming across the crash site of a downed communications satellite, but I'm short a lot of details. If anyone has any ideas, I'd love to hear them. Just a few starter questions, if you think of any more, feel free to throw them in: 1. How big is a modern comm satellite in mass and dimensions? 2. How big of a crater would one leave? 3. Would the crash start anything flammable on fire nearby, like grass or buildings? 4. How far away would you be able to see its re-entry? 5. How close could you be and safely see it? 6. What would be left of the satellite? Would any of the electronics still function or would they be melted beyond repair? 7 If satellites become smaller because of shrinking of computer chips, how would that impact all of these questions? Posts: 299 | Registered: Oct 2008
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1. How big is a modern comm satellite in mass and dimensions? For the larger ones, ten tons or more, the core minus antennas and solar arrays, about as big as a metro bus. 2. How big of a crater would one leave? At least comparable to diving a fully-loaded jetliner into the ground at full throttle from a height of 30,000 feet. 3. Would the crash start anything flammable on fire nearby, like grass or buildings? Depends on how much maneuving fuel it has remaining onboard, some use hypergolic fuels, which violently explode on contact with each other. Then there's the heat of reentry, which could or could not start fires, depending on what's left of the satellite and how much heat it retains. 4. How far away would you be able to see its re-entry? Nighttime, from most of a hemisphere under nominal weather conditions. Daytime, depending on the angle and force of reentry and orientation to the sun, from hundreds of miles away. 5. How close could you be and safely see it? Probably within a few hundred feet behind cover from flying shrapnel and fuel. 6. What would be left of the satellite? The densest and most reinforced parts would certainly survive. See reentry of Mir for details. Would any of the electronics still function or would they be melted beyond repair? Probably nothing sensitive to heat or impact would survive. 7 If satellites become smaller because of shrinking of computer chips, how would that impact all of these questions? Geostationary comsats are becoming larger to handle more circuits. Molniya orbit comsats, too. Low Earth orbiting satellites are becoming smaller but they function in clusters.
Most comsats orbit in the Clarke Belt at geosychronous alititude. One is highly unlikely to be brought down, insufficient onboard fuel for a deorbit burn. Barring a massive external force, one is more likely to stay where it is for a relatively long time. When a geostationary comsat is decommissioned, a small engine capable of raising it a couple hundred miles lifts it into a parking orbit where it stays for however long that orbit is stable.
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Two extraordinary, illustrative pictures from NASA'a Astronomy Picture of the Day archives. Caution, APOD is another fascinating site that takes time away from writing. Great pictures, though.
48 years of spaceflight, earliest surviving NASA satellite in orbit and ISS with most recent upgrade;
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well it will most likely have toxic fumes from the fule, it will be very unstable to be near and will be cordoned off be authorities i asked our EOD team in AFG once anout such an situation
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Hydrazine is one toxic rocket fuel used in thrust engines. The OSHA vocational exposure recommendation is rated at 1 part per million. The industry standard generally allows for 4 ppm. The threshold of aroma is 3 ppm. Below 4 ppm, regular exposure has not been conclusively demonstrated to statistically increase the risk of cancer. At higher exposure levels, other health concerns present. For an extensive listing of health reports related to hydrazine toxicity see http://www.gasdetection.com/TECH/hydrazine.htmlPosts: 6037 | Registered: Jun 2008
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I think any but the most massive of communications satellites would burn up completely on reentry. These tend to be on the lightweight side, the better to reach the geosyn---the geo---the Clarke orbit.
The ones that survive to plague the ground lately are those nuclear-powered ones with shielding around their power source, ostensibly to protect the people on the ground when it does reenter.
Does it have to be a communications satellite? One of the big low-flying spy satellites might be a more fruitful source of story ideas, in particular the "spy" connections...
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No, it doesn't have to be a comm satellite, I was just using that as an example. Its purpose is actually much more complex than a comms satellite, perhaps allowing me an excuse to make it bigger and more heavily shielded and therefore more likely to survive re-entry. I'll have to consider toxic fumes, but there will be no gov authorities involved. The reasons for this are story-involved that I don't want to get into (partially because I haven't worked them out)
Posts: 299 | Registered: Oct 2008
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Toxic fumes would not be as big a deal if the onboard fuels were LOX and LOH, or ETOH and something-something else as the oxidizer (omitted to avoid giving anyone any dangerous ideas). Hydrazine is unstable over relatively short mission times, too long for the average 15-year mission profile for comsats. Solid fuels are generally longterm stable, but once the candle's lit it can't be turned off and on the way liquid fuels can.
One likely scenario that would avoid issues of atmospheric reentry and the resulting burnup and avoid immediate government attention and could conceivably preclude an oceanic splashdown, a crash at a land-based site, is a launch failure and failure of a self-destruct safety. Nothing nominally out of Canaveral, though. Say, a retrograde launch of a circumpolar satellite, many of which are spy satellites or Earth surveyors and mappers. A Molniya orbit is one with a highly eliptical orbit with a period of about 12 hours but spends most of it's time over an intended area resulting from apogee dwell.
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Thanks guys, I got sidetracked with revisions for a few days, but I'll be back on this story in a few days, then I might have more questions. Posts: 299 | Registered: Oct 2008
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If the satellite fell during the day, what would you see? A smoke trail?
If the satellite fell fairly nearby, say a quarter mile away, what would it sound like? I would expect a boom on impact, but would it make any noise while it falls?
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There'd probably be a sonic boom as it fell.
Falling in daylight isn't going to mean it won't be burning. The flames just won't be as bright as they would be if it fell in the night. So, smoke and flames.
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