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From: disprep@lonex.radc.af.mil (Disaster Preparedness)
Newsgroups: sci.space
Subject: Re: Solar Impact Mission.
Message-ID: <1991Feb5.185021.10001@lonex.radc.af.mil>
Date: 5 Feb 91 18:50:21 GMT
References: <1991Feb4.111437.9283@helios.physics.utoronto.ca> <1991Feb4.172846.3706@zoo.toronto.edu> <1991Feb5.154205.29266@engin.umich.edu>
Sender: andrewsh@lonex.radc.af.mil
Organization: Rome Laboratory (US Air Force), Griffiss AFB, NY
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In article <1991Feb5.154205.29266@engin.umich.edu> theslim@caen.engin.umich.edu
writes:
>In article <1991Feb4.172846.3706@zoo.toronto.edu>, henry@zoo.toronto.edu
>(Henry Spencer) writes:
>> ....
>>
>> For really tight turns, what you want is a waverider design that can fly
>> at high hypersonic speeds in an atmosphere.  Then you can do a right-angle
>> turn or even a 180 around any planet with a substantial atmosphere, e.g.
>> Venus.  Aerodynamic forces do a much better job of holding you down during
>> the turn than gravity.  This also lets you use Mars rather than Jupiter
>> for outer-planets missions, which is nice because Jupiter's Van Allen belts
>> are a major hassle for Jupiter gravity assists.
>> --
>
>I've heard about this kind of thing-- it sounds like a neat idea although
>the aerodynamics of going that fast through an atmosphere would be rough,
>not to mention the materials the waverider would have to be made out of.
>Also, you'd better carry along big thrusters for correcting any errors
>made in the manuever.  Anyone in netland doing any research with high
>velocity waveriders?
>
>One of the more interesting waverider missions I've heard of was using Mars for
>a gravity assist to get out to Pluto.  I don't have the velocities handy,
>but I remember the time figure as being about 4 years to go from Earth to
>Pluto using that kind of trajectory.
>
>---

     These are very interesting ideas that, I agree, would allow a probe
to change its direction in a hurry.  The problem I see is that when the 
vehicle enters an atmosphere, it loses kinetic energy in favor of thermal
energy.  The idea of using this aero-assist method would seem to work okay
for a solar impact mission, but I don't see how a probe could reach Pluto
in four years after losing kinetic energy.  Does it kind of bounce off
of the Martian atmosphere and gain a whole bunch of kinetic energy somehow
(not at all obvious to yours truly)?  Or does the probe's proximity to the
planet allow for a greater gravitational kick that more than overcomes the
loss to heat?  Whatever the reason, I'm certain Mr. Spencer can set my
misgivings straight.

- Andy

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* Harold G. "Andy" Andrews II, 1Lt, USAF *  "Many the man whose punctuality   *
* andrewsh@lonex.radc.af.mil             *   serves only to warm his chair."  *
* Rome Laboratory/IRRE (USAF/AFSC/ESD)   *                                    *
* Griffiss AFB, NY USA 13441-5700        *    -- Leonard somebody or other    *
* (315) 330-7788 (AVN prfx 587)          *  (Not an official USAF viewpoint)  *
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