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**Derek Lyons**

(Henry Spencer) wrote:

In article . com,
John wrote:
During the few test shots of Trident missles that I have seen, I always
thought that the angle at which the vehicle flew was remarkable; like
nothing I had ever seen, save for the occassional errant Estes rocket.
The angle seemed close to 45 degrees, although I had no way of really
knowing, almost immediately after emerging from the water and ignition.

I wonder, though, if it actually ascends in that direction, or if that's
just a transient error -- perhaps something to do with the dynamics of
breaking the surface -- that the guidance system sorts out a second or
two later.

There can be attitude transients caused by hydrodynamic effects of the
passage through the water as well as the effects of breaking the
surface. ('Tail slap' as the missile exits is of particular concern.)
Polaris was acutely sensitive to this because of their need to perform
a roll maneuver immediately upon ignition.

In the early days they even tested a set of flow velocity sensors
mounted on the SSBN to attempt to predict wave action and the
calculate the best moment for launch!

They do tend to fly a steeper trajectory than is usual as well.
Partly to encourage seperation between birds (which are being salvoed
at short intervals) and partly as a safety measure to the get the bird
away from the boat as soon as possible.

Also, SLBM launches are typically filmed at much shorter ranges than
is usual for NASA launches - which messes with your ability to
estimate flight angle.

D.
--
Touch-twice life. Eat. Drink. Laugh.

-Resolved: To be more temperate in my postings.
Oct 5th, 2004 JDL