Hi Gary

My responses are in brackets...

Responding to questions:

>Ok assume the Mars crew have used
>centrifugal gravity to stay healthy,
>and wear counter-gravity suits to take
>up to 9 gees like Apollo.

I don't think Apollo took 9 gravities (might be wrong on this).

[apparently so, at both launch and on re-entry]

>I was wondering if you could aerobrake
>from 'fast' 100 day transfer orbits >into elliptical parking orbits.

The 11 km/sec entry that I quoted before was for a fast trajectory (Aldrin escalator orbit).

[aerocapture from an Earth-Mars cycler? Or is an escalator orbit something different again?]

A 160 km/sec entry is impossible to shield for. The very rough rule-of-thumb is entry speed in km/sec times 1000 gives peak shock layer temperature in degrees Kelvin, i.e. 160 km/sec gives 160,000 deg.Kelvin.

[OUCH!!!]

Uranus is not very interesting in terms of planetary science.

[Not interesting to you maybe... but I get the point. I was thinking of the old story. Alan E. Nourse i think wrote it.]

However Neptune is very interesting because of it's moon Triton.

[Neptune is interesting in itself too, but Triton is easier to study. I'd love to see long-duration nuclear ramjet missions to all the gas-giants though... *sigh*]

>Does your code go that far, or does it bust?

I am currenty doing feasibility studies for Neptune aerocapture to Triton.

[Sounds like an NTR boosted probe - else an chemical powered orbiter mission would take well over a decade if it bounced around the Inner System then Jupiter to build up speed. I thought the JPL was going for the SEPS propelled probe pictured at the web-site - not aerocapture friendly for the kind of speeds involved surely...]

>Galileo fell into Jupiter with a relative
>velocity of 47.5 km/s and survived...

The ancestor of the branch that I work at designed the Galileo probe (the original designers are all retired from NASA). I'm using Galileo probe flight data to validate my software. The Galileo probe was actually going 47.3691 km/sec [atmosphere relative] at 450.0 km altitude [zero altitude is referenced to 1 bar pressure]. The inertial entry speed was 59.92 km/sec [Jupiter rotates fast]. The success of the Galileo Probe was one of NASA's greatest triumphs. However the Galileo Probe was able to enter Jupiter's atmosphere at such high speed because that atmosphere was mostly hydrogen which has enormous heat capacity. Had the probe entered the Earth's (or Titan's) mostly nitrogen atmosphere at that speed then it would have vaporized.

[ah I see... since Neptune's air is mostly H as well and its gravity is lower so the atmosphere is "softer" can higher entry speeds be achieved?]

[What computer requirements does the code you use need? Is there a version for interested amateurs, like me, to play with available??]

Adam