[AR] Re: Turning after launch
- From: Henry Spencer <hspencer@xxxxxxxxxxxxx>
- To: Arocket List <arocket@xxxxxxxxxxxxx>
- Date: Mon, 16 Apr 2018 12:33:49 -0400 (EDT)
On Mon, 16 Apr 2018, Ed LeBouthillier wrote:
...With vertical launch systems, the rocket is immediately turning to go
on a trajectory towards the target. If you think of it, a target might
be downrange many miles (30-40 miles for example) but even if it's at
altitude, the target might only be 30K-40K ft. This means that the angle
to point toward the target is atan(40000/(40*5280)) = 10-ish degrees.
So, most of the time, the target is farther downrange than gaining
altitude.
Although most any modern SAM won't fly directly at the target, unless the
range is very short (or the guidance system is old and stupid). Even with
winged missiles, you usually get longer range if the missile climbs into a
semi-ballistic trajectory that comes *down* onto the target. (There is
also a tactical bonus: even alert pilots tend to keep a much sharper
watch for missiles coming up at them from below, so coming down from above
is rather more likely to take the pilot by surprise.)
Mind you, this doesn't change the desirability of an immediate turn, it
just reduces the angle of the turn somewhat.
Even space launches would start turning almost immediately -- look at the
videos of Apollo LM ascents from the Moon -- were it not that their final
velocities are so high that they have to get completely clear of the
atmosphere fairly early.
Henry
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