What maximum mach number can be achieved by high speed hypersonic aircraft space rocket? Can they achieve 30 mach number? What might be the damage impact on their rocket body if attain overlimit?
Typical re-entry Mach number for Apollo flights was M=24. This is the reason for the very thick metal shield that was used to protect the cabin. This shield would simply evaporate (evaporation cooling). The gas temperature would reach incredibly high temperature. From Bernoulli one finds without assuming ionization or dissociation of air To/T=1+0.2M^2=181 at M=30. The stagnation temperature would reach 50.000 K for surrounding temperature T=300 K. Dissociation and ionization would lower this to temperature of the order of 15.000 K. The wall recovery temperature would be of that order of magnitude. Hence a conventional rocket with M=30 is almost impossible. Even for a scramjet at M=7 or M=8 we expect already temperatures of a few thousand degrees (after dissociation). Indeed it is extremely difficult to keep such an engine "alive" (even for short times). The great advantage of scramjet above a normal rocket is that it carries the fuel but gets the oxygen from the surrounding air. This dramatically decreases the engine weight at take-off. However, such engines are currently launched from an aircraft, which also reduces the power for take-off.
Abraham answer is absolutely correct. Apart of those answer I would like to add some basic things like we know the intensity and size of shock waves generally vary with the mach number. Aerodynamics characteristics entails airflow maximum disturbance by imposing a high back pressure at the exit of the engine inlet and consequence effect on rocket body will incur if mach number is more than 7 or 8. There is a drag and lift issues I think, drag coefficient to increase suddenly causing a dramatic increase in total drag and changes to the airflow over the flight control surfaces will lead to deterioration in control of the aircraft in term of lose lift, pitch heavily nose down and altitude might be lost, tubes and established assembly operating at high mach number will be automatically damaged, leaking could cause in body, and consequently hurting body can no longer bear the strain of speed.
Ashish
Prof. Hirschberg,
A slight correction: the Apollo reentry capsules used an ablating epoxy-based material for their forward-facing thermal protection.
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