Adam asked some questions.

What would the temperature of Galileo's re-entry shockwave peaked at?

The shockwave temperature for the Galileo Probe ranged from the free stream
temperature (undisturbed Jupiter atmosphere) of 150 deg. Kelvin to the shock layer temperature of about 16,000 deg. Kelvin (Water melts at 273.15 deg. Kelvin). A temperature of 16,000 deg. Kelvin is hotter than the Solar photosphere and would vaporize anything, e.g. tungsten. The Galileo orbiter would have completely vaporized long before it reached that temperature. The peak deceleration for the Galileo Probe was 230 G. Had the Galileo orbiter not been vaporized, it would have been crushed. The peak total unblocked heat flux for the Galileo probe was about 15 kilowatts/cm^2. The probe survived Jupiter entry because of its carbon phenolic heat shield. The outer layer of the heat shield outgassed thus keeping the hot shocklayer plasma away from the probe's outer surface. Also this same gas emitted from the heatshield's surface was mostly an opaque carbon gas that kept the shocklayer radiation from reaching the probe's outer surface. Consequently the probe's outer surface never got much hotter than 3500 deg. Kelvin. After completing its mission, the Galileo Probe descended into the Jovian atmosphere which got hotter and hotter as the probe descended deeper (this is due to isentropic compression). Eventually the ambient temperature of the atmosphere got so hot that the probe vaporized into monoatomic gas. The Jovian atmosphere has huge convection cells where the atmospheric gas is circulated to above the clouds where it reaches cryogenic temperature. At that altitude, simple chemical molecules can form which are the basis for the pretty colors that Jupiter has when seen from Earth. Eventually these molecules are pulled down deep into the Jovian atmosphere where they disassociate back into monoatomic gas. Jupiter could be thought of as a small star that never lit up. Needless to say, designing spacecraft to descend into Jupiter's atmosphere is one of the coolest things that a rocket scientist can do (and they actually pay us to do this as well!).

What do you think of Buzz's Starbooster concept?

I heard Dr. Aldrin present this concept during a lecture that he gave at NASA Ames. It's an interesting idea. I have an issue with his original concept in that too much metal is being hauled into Low Earth Orbit. The Atlas-V missile has enough structure to withstand the acceleration loading and dynamic pressure for entry into orbit. Aldrin suggests putting that structure as a core within an air frame. A better idea would be to simply pull the engines and fuel tanks from an Atlas-V and mount that within a lightweight frame. IMHO, an ideal second generation Recoverable Launch Vehicle (RLV) would be a Two Stage To Orbit (TSTO) bimese or biamese design where the booster and orbit vehicle outer structures (air frames) were identical. By having identical airframes, there would really only be one vehicle type to design and service. The basic air frames would be hollow (like a knight's suit of armour). One would then insert a high thrust propulsion core into the booster and a high Isp propulsion/payload core into the orbit vehicle. The mind set is to think of a F-16 fighter plane. The F-16's turbojet motor is mounted on rails inside the airframe. A skilled crew with the right tools can swap engines in about 20 minutes. The down side for my concept is the booster would carry too much thermal protection. However the cost for this added mass would be more than offset by savings from vehicle commonality yielding lowered ground servicing costs. One could employ a vehicle life strategy were young air frames are used for orbit vehicles. After they got beat up from multiple reentries, these same air frames could then be used for boosters. Because the cores were removable, it'd be a snap to service the propulsion systems or upgrade them to better performing versions.

Gary