"Holo" - GLL "Cold" , also called
"Holo" (hypersonic flying laboratory).
- similar to Hyper-X 43A for scramjet research.
FIrst flight in 1991 and seven by 1999. Contract
in 1998 with NASA. Scramjet runtime up to 77sec.
and reached 6.49 Mach.
Aerospike engine in RLV
History section Although, the
X-33 program was canceled, the engine
tests are considered a success. Aerospikes
are ideal for SSTO since they provide
efficient performance at ground atmospheric
pressures all the way to vacuum conditions.
However, SSTO development has been dropped
by NASA in favor of 2 stage systems. In
this case, each stage can have separate
engines, each designed specifically for
the conditions it will run under.