bobkrech
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Mach 2 is quite mild. I would not expect much aeroheating during a typical rocket flight.
Check out https://www.aerospaceweb.org/design/scripts/atmosphere/ With is calculator you can figure out the amount of heat that might be transferred to the structure at altitude.
At Mach 2 the air flow behind the shock is ~200C (~400F) at sea level. While the air is hot, the density is low compared to a solid structure. The heat transfer is proportional to the delta T, the density of the air, and the heat transfer coefficient, and the thermal conductivity and heat capacity of the underlying structure. As we said before the heating is directly proportional to the air density which drops quickly as you increase altitude, and as the cube of the Mach Number. If you look at the calculator, you will see the term equivalent Mach number. At sea level, the equivalent Mach number is the actual Mach number. As the altitude increases, the Equivalent Mach number decreases, and on a comparative basis, the ratio of the heating at altitude is reduced the ratio for the Equivalent Mach Number divided by the actual Mach number squared. Just play with the calculator. Look at the recovery temperature as a function of altitude at Mach 2. At sea level it's 428 F, but at 7.5 miles it's only 208 F. That's at bit much for aluminum continuously at sea level but fine at 7.5 miles. At Mach 3, it's 890 F at sea level but a much lower 555 F at 7.5 miles. Way too hot for aluminum but fine for titanium or stainless steel. If you push Mach 4, it gets to hot for almost all metals. 1536 F at sea level and still 1041 F at 7.5 miles. Heat capacity in a well designed rocket can handle the transient heating but nothing made of metal is going to that that temperature at sea level, so you need ceramics.
When you go fast in the atmosphere, you really have to do a transient calculation that includes heat transfer, thermal conductivity and heat capacity to determine if a structure will survive and for how long.
Check out https://www.aerospaceweb.org/design/scripts/atmosphere/ With is calculator you can figure out the amount of heat that might be transferred to the structure at altitude.
At Mach 2 the air flow behind the shock is ~200C (~400F) at sea level. While the air is hot, the density is low compared to a solid structure. The heat transfer is proportional to the delta T, the density of the air, and the heat transfer coefficient, and the thermal conductivity and heat capacity of the underlying structure. As we said before the heating is directly proportional to the air density which drops quickly as you increase altitude, and as the cube of the Mach Number. If you look at the calculator, you will see the term equivalent Mach number. At sea level, the equivalent Mach number is the actual Mach number. As the altitude increases, the Equivalent Mach number decreases, and on a comparative basis, the ratio of the heating at altitude is reduced the ratio for the Equivalent Mach Number divided by the actual Mach number squared. Just play with the calculator. Look at the recovery temperature as a function of altitude at Mach 2. At sea level it's 428 F, but at 7.5 miles it's only 208 F. That's at bit much for aluminum continuously at sea level but fine at 7.5 miles. At Mach 3, it's 890 F at sea level but a much lower 555 F at 7.5 miles. Way too hot for aluminum but fine for titanium or stainless steel. If you push Mach 4, it gets to hot for almost all metals. 1536 F at sea level and still 1041 F at 7.5 miles. Heat capacity in a well designed rocket can handle the transient heating but nothing made of metal is going to that that temperature at sea level, so you need ceramics.
When you go fast in the atmosphere, you really have to do a transient calculation that includes heat transfer, thermal conductivity and heat capacity to determine if a structure will survive and for how long.