[extropy-chat] SPACE: Deep Impact shows strong spectral lines...

[Mike Lorrey]

--- spike <spike66 at comcast.net> wrote:

> > bounces at lists.extropy.org] On Behalf Of Mike Lorrey
> > 
> > ... it appears that using
> > Tempel as a bus for an orbital transfer can happen about every 12
> > years...
> > 
> > Mike Lorrey
> 
> When you say "using Tempel as a bus" it sounds like you are
> somehow riding it, or it is providing something other than
> propellant.  If you want to land on Tempel, you have already
> provided the delta V to match its orbit.  In that case, you
> would end up at its aphelion with or without the comet.  
> 
> It isn't clear to me why you would need the comet at all,
> unless it is to fill your propellant tanks with 
> whatever material available there, probably water, maybe
> the methane.  Of course you will still need to come up
> with a lot of energy to heat the propellant, which I
> am assuming you would do via nuclear fission.  Is that
> what you had in mind?

The evidence from the impactor is that exposure of the subsurface to
sunlight is sufficient to evaporate significant quantities of material.
The surface layer of dust is somewhere between 1-10 meters thick.
Sinking well bores into the ice and heating them with solar energy
should be sufficient to develop a significant flow of fluid at low
pressure (<100 milibars). 

The water could be electrolyized over a 2 year period by an SP-100
class reactor on the journey outward into its constituents, and useful
organics can be distilled out of solution prior to electrolysis to
provide other fuels. (ethane, methanol, and acetylene are all useful)
The mission might choose to leave significant stores of purified fuels,
along with the purification equipment, on the comet for future missions
lacking in refining equipment.

Tempel reaches perhilion about 20 million miles from Jupiter orbit, so
the extra delta v gained by refuelling for that jump won't need to be
boosted from Earth or refined from  lunar materials. The scienfic gains
of spending time examining the comet in depth on the surface will also
pay significant dividends (plus providing the ability to lay claim to
its resources for the venture that lands on it first).

Getting to Jupiter is only a small part of the necessary delta-v for
the whole mission, maybe 30-40% at most. You need to brake into Jupiter
orbit, then escape again from Jupiter orbit, then brake all the way
down on return to Earth orbit, otherwise you'll be showing up near
earth with at least 30,000 mph of velocity, plus the 25,000 you'll be
picking up as you fall into earth's gravity well..

Here is the delta-v budget for the mission:

Leaving Lunar orbit: ~3.4 km/s - escape from Earth/Moon system
Trip to Tempel perhilion:  8 km/s   - climbing up the Sun's gravity
well to rendesvous point
Landing on Tempel: ~10.5 km/s - Must match Tempel velocity, about 23k
mph faster. 

Everthing below this point comes from refueling on Tempel and possibly
other locations:
Transferring from Tempel orbit to Jupiter-Sun orbit: 5.1 km/s
Entering orbit around Jupiter: up to 49 km/s (aerobraking and gravity
assist should contribute to this)
Orbital maneuvering around Jovian system: undetermined, this may
involve landing on one or more small ice moons to refuel again.
Escaping Jupiter orbit: up to 49 km/s (gravity assist should contribute
to this)
Return to Earth/moon system: 27 km/s

Refueling at Tempel will make such a mission possible. Using Mars as a
gravity assist to help reach Tempel is also a possibility, as is using
it to assist in braking the return to Luna orbit. Return trip after
escaping Jupiter would be primarily by braking with solar sail.

Mike Lorrey
Vice-Chair, 2nd District, Libertarian Party of NH
"Necessity is the plea for every infringement of human freedom.
It is the argument of tyrants; it is the creed of slaves."
                                      -William Pitt (1759-1806) 
Blog: http://intlib.blogspot.com


		
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