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Hermes II is expected to reach high speeds in low atmosphere: approx Mach 3.5 at just 10,000 ft when burn out occurs. At these high speeds, the stagnation point temperature of the air is extremely high:
$$
| T_{stag} = T \left(1 + \frac{\ |
|
gamma | gamma - 1 }{2} M^2 \right) = |
|
268 | 268 \left( 1 + \frac{1.4 - 1 }{2} 3.5^2 \right) = |
|
924 K $$The service temperature of aluminium is on the order of 580K, for steel it is 1200K.
Does that mean that a steel nose cone is sufficient to withstand the flight? Not necessarily.
We need to understand how the