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The Delta IV Heavy recently launched NORL-65 to a low Earth orbit. Some of these missions will be in the range of 390 km altitude with circular orbits. Plus, the Delta IV Heavy is a big rocket, with a LEO payload of 22 tons.

Considering that it's a sensitive payload, how do you avoid it crashing into a random place on Earth when the orbit decays? I presume they would strive to avoid that for obvious reasons. Can such large masses burn up in the atmosphere? Is that even an option for a large telescope? Do people seriously entertain the idea of a controlled re-entry? Or do they use a disposal orbit? It's a classified mission so there's probably no official word on it.

What are the options that are seriously considered for that kind of mission?

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    $\begingroup$ I guess you nailed down the options pretty well. $\endgroup$ – gerrit Aug 30 '13 at 13:43
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    $\begingroup$ @gerrit But is de-orbiting an option? Maybe you can engineer a satellite to burn up? I don't know, that's what I'm curious about. And can you have a controlled entry? I don't know. But maybe these should have been broken up into more specific questions, which would make it more clear. $\endgroup$ – AlanSE Aug 30 '13 at 14:04
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De-orbiting isn't too bad of an option really. While a really large satellite would still have some pieces intact, it by and large will not be completely intact. Furthermore, the most sensitive things on a spacecraft tend to be the computers, antennas, and cameras. Of those, the only remotely likely to survive re-entry is the cameras, most likely only the mirrors from said camera.

Furthermore, most LEO satellites are reasonably well designed to break up. Unprotected aluminum doesn't survive reentry very well, and it is what most LEO satellites are composed of. Practically speaking, one has to design purposely to have anything survive re-entry, otherwise all you get is chunks.

The destruction procedure for classified material for the US in general is explained in NISPOM, which states:

5-705. Methods of Destruction. Classified material may be destroyed by burning, shredding, pulping, melting, mutilation, chemical decomposition, or pulverizing (for example, hammer mills, choppers, and hybridized disintegration equipment). Pulpers, pulverizers, or shredders may be used only for the destruction of paper products. High wet strength paper, paper mylar, durable medium paper substitute, or similar water repellent papers are not sufficiently destroyed by pulping; other methods such as disintegration, shredding, or burning shall be used to destroy these types of papers. Residue shall be inspected during each destruction to ensure that classified information cannot be reconstructed. Crosscut shredders currently in use capable of maintaining a shred size not exceeding 1/32 inch in width (with a 1/64 inch tolerance by 1/2 inch in length) may continue to be used. However, any crosscut shredders requiring replacement of the unit and/or rebuilding of the shredder blades assembly must be replaced by a crosscut shredder on the latest NSA Evaluated Products List of High Security Crosscut Shredders. The list may be obtained from the CSA. Classified material in microform; that is, microfilm, microfiche, or similar high data density material; may be destroyed by burning or chemical decomposition, or other methods as approved by the CSA.

While each classified program can add in additional standards, I believe that uncontrolled re-entry of most spacecraft falls within this destruction principal.

Furthermore, the re-entry for any satellite is usually many years after launch, at which point in time the classification parameters aren't as important (Most stuff of this nature can be declassified after 25 years). Of course, the mentioned 390 km orbit doesn't quite fit in to the 25 year range, but I would expect that the satellite's orbit will be raised if possible.

Finally, the re-entry of a satellite can be controlled, it just takes a bit more work and a lot of planning. MIR was successfully deorbited, and I suspect any satellite can be deorbited in a controlled fashion.

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    $\begingroup$ In fact for large things they try to tumble them as they re-enter for more friction and more burning upping. $\endgroup$ – geoffc Aug 30 '13 at 16:23
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    $\begingroup$ @geoffc: Wouldn't tumbling reduce heating by distribution of the heat? First one surface, then another? $\endgroup$ – Everyone Aug 30 '13 at 17:45
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    $\begingroup$ @Everyone: It actually causes it to break apart easier, followed by everything heating up quicker. $\endgroup$ – PearsonArtPhoto Aug 30 '13 at 18:12
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    $\begingroup$ @Everyone And smaller bits have more surface area, per unit volume and thus heat up faster and melt. $\endgroup$ – geoffc Aug 30 '13 at 18:41
  • $\begingroup$ Got it. I wasnt thinking of tumbling as force happening on heated weakened surfaces. TY the both of you $\endgroup$ – Everyone Aug 30 '13 at 19:15

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