Aircraft and rocket refrigeration Which air-cycle cooling system is used for very high-speed applications such as supersonic aircraft and rockets?

Introduction / Context:
Air-cycle (reverse Brayton) systems in aviation come in multiple configurations. As flight speeds and altitudes increase, higher pressure ratios and more effective heat rejection are needed to achieve the required cabin or equipment cooling.

Given Data / Assumptions:

• Supersonic aircraft and rocket environments demand high effectiveness and lightweight systems.
• Bleed-air temperatures and ram effects can be very high.

Concept / Approach:
The regenerative air cooling system incorporates heat exchangers and reheat/recool steps to extract more work in the turbine and thereby increase the temperature drop of the air supplied to the cabin or payload bay. This configuration is suited to very high-speed regimes where simple or even boot-strap systems may not provide adequate temperature depression.

Step-by-Step Solution:
Compare variants: simple < boot-strap < regenerative in achievable pressure ratio and cooling effectiveness at extreme conditions.Supersonic/rocket → very high stagnation temperatures → need additional stages/heat exchange → regenerative best choice.

Verification / Alternative check:
Aerospace texts map system selection to flight envelope; regenerative schemes are cited for the highest speed ranges.

Why Other Options Are Wrong:
(a) and (b) may suffice for subsonic/transonic transports, not extreme regimes. (c) is a descriptive phrase, not a standard system. (e) evaporative cooling is not used in these aircraft ECS due to icing and water management issues.

Common Pitfalls:
Assuming the boot-strap system is universal; it dominates transport jets but not necessarily supersonic/rocket applications.

Final Answer:
regenerative air cooling system