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Wikipedia writes to say Low Earth Orbit spans the altitude from 160KM above Earth through 2000KM above Earth.

Launch vehicles appear to be highly stream-lined. Yet only the first few score KM (as far as the Karman Line) are in atmosphere. To the best of my comprehension, dead-weight is a no-no on launch vehicles/systems.

The additional mass of aerodynamic sheets may be necessary when the payload for a launch must be protected from the elements. Yet in all other cases it probably constitutes dead-mass.

  • Is the streamlining of a launch vehicle/stages/components worth the additional fuel required to carry it beyond the Karman line?

  • What is the earliest launch vehicles may/should jettison the streamlining dead-weight? (This would probably have to be on a case-by-case basis, but any recommended guidelines/parameters ... ?)

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1 Answer 1

This dead weight is called "fairing". The time to do payload fairing separation is determined by heat flux from the air (maximum free molecular heat flux) that can be tolerated by the payload (and its more sensitive parts), and by the mass margins provided by the launch vehicle, as well as impact point constraints downrange (you don't want lawsuits from angry relatives). Nobody wants to carry fairing any longer than absolutely necessary. The exact timings may vary from 150 seconds to 350 seconds after lift-off, speaking from memory.

To achieve separation, a carefully orchestrated and tested sequence of explosive bolts, detonation cord and separation springs is used.

The exact method of "streamlining" depends on the launch profile. For instance, drag reduction may include a shock wave aerospike for ballistic missiles that are programmed to get out of Dodge and 'clear the datum' A.S.A.P.

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