[extropy-chat] Pluto New Horizons launch -getting ready

[Bret Kulakovich]

Hi spike!

If we just accept the necessary increase in mass to do this (since  
we're forgoing fuel to land, why not), could we not build some sort  
of kinetic ladder for the lander to step down?

If there were multiple projectiles of different materials landing in  
(very) rapid succession, then we could build an environment starting  
at the surface and working its way up to the actual "lander" in the  
milliseconds before impact. This environment would gradually increase  
the density of the medium the craft was passing through until it  
reached the surface. Sort of like skidding to a halt. It could be  
done with either materials or perhaps other forms of energy release,  
depending on what was more economical to carry. If you consider the  
timing necessary to reach critical mass in a fission-fusion-fission  
reaction, I think this would be equally as "easy".

Thoughts?

Bret K.


On Feb 16, 2006, at 1:36 AM, spike wrote:

> bounces at lists.extropy.org] On Behalf Of Robert Bradbury
> Subject: Re: [extropy-chat] Pluto New Horizons launch -getting ready
>
> Sounds like you need a combination orbiter + lander.  Let the  
> lander just
> worry about getting signals up to the orbiter and the orbiter worry  
> about
> getting them back to Earth.  But they you still have the deceleration
> problem again.  I think an inflatable antenna on a hard-impact  
> lander might
> be the way to go.  The crater problem can be solved if you can  
> bring it in
> at a low angle and/or let it bounce/roll along until it came to a
> stop...Robert
>
>
> Robert and all space fans,
>
> I thought this over and remembered a project I was on about fifteen
> years ago.  When the kinetic energy of a projectile is large with
> respect to the sum of the heat of fusion plus the heat of vaporization
> of the projectile material, you are in what is termed the hydrodynamic
> impact regime.  Upon impact, a compression wave is sufficiently  
> violent
> to break the chemical bonds in both the projectile and the target.   
> The
> projectile and the target are vaporized in this regime, regardless
> of the material of either the projectile or the target.
>
> Above the hydrodynamic impact regime velocity, increasing velocity
> of the projectile does not punch a deeper hole in the target, it
> only punches a wider hole.  This explains why the craters on the
> moon are wide but not particularly deep.  It also explains why
> super high speed armor piercing shells are long skinny things: the
> length is all that matters above a certain speed.
>
> On the project previously mentioned, the velocities we were working
> were all in the 3 to 4 km/sec range.  This was sufficient to
> enter the hydrodynamic impact regime for the second highest
> energy of vaporization material we know of: tungsten.  Only
> carbon is higher, and that not by much.
>
> So if we were to try an impact landing on Pluto,
> we would still need to reduce the relative velocity down to
> about that of a high-speed rifle bullet, which is in the 0.4
> to 0.6 km/sec range.  You know what happens to a rifle bullet
> when it hits a target; you can dig out the slug usually.  It's
> messed up, but still mostly there.
>
> So if we attempt to land on Pluto, the required deceleration
> is not 14 km/sec but rather only about 13.5 km/sec.
>
> If we suggest something like what one poster proposed, to
> drop a cable and allow the drag across the surface to
> decelerate the vehicle, keep in mind that it might take
> a lot of cable.  If the relative velocity of spacecraft
> to planet is 14 km/sec and it is strong enough to withstand
> a tension of 100 times the mass of the vehicle, you need to
> reel out 14 km of cable in the first second after the craft
> passes the planet, 13 km in the next second, and so on, for
> a total of about 120 km.  This assumes you can somehow
> maintain a nice steady 100 G deceleration, and you
> somehow solve the problem of hydrodynamic impact
> vaporizing the cable upon impact.
>
> If you decide to go the route of chemical rocket
> deceleration, you have a problem of how to keep
> the fuel from freezing if you use hydrazine or
> how to keep it from boiling away if you use
> cryogenic fuels.
>
> Of all the possibilities, the one most attractive
> to me is to send it out on a Hohmann orbit, which
> obviates most of the fuel problem, since the relative
> velocity of spacecraft to Pluto is low upon arrival.  The
> main drawback to this approach is that it takes about
> 62 years to get there, assuming gravitational assist
> from Jupiter.  That would make me 107 by the time it
> gets there, assuming we launch right away.
>
> spike
>
>
>
>
>
>
>
>
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