[AR] Re: Michigan Announces a vertical launch facility
- From: Henry Spencer <hspencer@xxxxxxxxxxxxx>
- To: Arocket List <arocket@xxxxxxxxxxxxx>
- Date: Sat, 1 Aug 2020 00:15:32 -0400 (EDT)
On Fri, 31 Jul 2020, Rand Simberg wrote:
*Most* orbital launches fly over populated areas eventually; it simply
can't be avoided. Every launch from the Cape to ISS flies over Western
Europe, which is one great big populated area.
Yes, but worth noting that at that point, you've already dropped (or
recovered! That's new) the first stage, your IIP is moving like a
banshee, and the chances of anything surviving an...unexpected entry are
low.
Not necessarily. Yes, toward the end of ascent to orbit, the debris
footprint sweeps so rapidly over the surface, far downrange, that the
chances of actually hitting anything specific are minimal (which is good,
because that footprint passes over a lot of surface). In fact, in a
launcher with three or more stages, it's not uncommon for the destruct
system to be on the next-to-last stage, on the theory that the final stage
doesn't really need it for that reason.
*However*, Western Europe is not far enough downrange from the Cape to
invoke this clause. :-) Shuttle flight 51F, the one that lost an SSME
partway up due to a misbehaving sensor, could have dropped its ET on
Europe if a second SSME had gone out. And the same sensor on another
engine was in fact starting to act up, but the crew overrode the sensor
system to prevent a second shutdown. (51F was pre-ISS, but was going to a
similar orbit for other reasons.)
Henry
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