[AR] Re: BFR Noise
- From: Henry Spencer <hspencer@xxxxxxxxxxxxx>
- To: Arocket List <arocket@xxxxxxxxxxxxx>
- Date: Sat, 1 Oct 2016 14:38:29 -0400 (EDT)
On Sat, 1 Oct 2016, Henry Vanderbilt wrote:
Sounds like you were three miles away, allowing for the engines starting
a couple seconds before T=0. Three miles seems to be a canonical
USG-rules safety distance for spectating rocket launches - they made us
sit three miles away for the several DC-X flights I saw ...
It may perhaps have become a rule of thumb, at least for some people, but
for LC-39 the three-mile distance was set because a worst-reasonable-case
explosion of a Saturn V would be dangerous out to just about there.
(People later discovered one complication: the ideas about acceptable
distances hadn't considered the extra complications from a vehicle with
engine-out capability. Saturn V first-stage guidance was open-loop, just
following a preprogrammed tilt schedule -- any trajectory errors
accumulated in first-stage flight would be cleaned up after max-q, when
closed-loop adaptive guidance took over just after staging. But this
meant that although the first stage could carry on after losing an engine,
it made no attempt to compensate for sideways drift that would result, and
the slower ascent gave this more time to accumulate. The resulting path
followed by the if-it-explodes-now debris footprint was "quite a strange
curve", and if you lost engine #3 early, the footprint center could pass
near the VAB.)
Henry
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