[AR] Re: Turning after launch
- From: "John Dom" <johndom@xxxxxxxxx>
- To: <arocket@xxxxxxxxxxxxx>
- Date: Mon, 16 Apr 2018 19:07:23 +0200
Isn't that called a gravity turn considering orbital/space launches. Those
are slow and have little to do with the speedy trajectory switch observed
with SAMs or cruise missile launches. This quick turn was not done say 10
years ago looking at YouTube.
John
-----Original Message-----
From: arocket-bounce@xxxxxxxxxxxxx [mailto:arocket-bounce@xxxxxxxxxxxxx] On
Behalf Of Henry Spencer
Sent: maandag 16 april 2018 18:34
To: Arocket List
Subject: [AR] Re: Turning after launch
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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