SpaceBanter.com - View Single Post - NASA changing opinion on the Direct HLV launcher.

**Jeff Findley**

In article 28310113-d909-48be-a613-e0d31aae4682
@c10g2000yqh.googlegroups.com, says...

TRL-5 - Technology Development
TRL-7 - Technology Demonstration

The ET has flown into space

Not in the configuration you propose.

Tail sitting aircraft and spacecraft have been demonstrated

Aircraft yes, they were abandoned during R&D as too dangerous.
Spacecraft, no, not a vehicle which flew as a glider, was towed, then
landed vertically under its own power. This is not TRL-7 or greater.

Aerospike engines have been demonstrated

On test stands at 1/10th the thrust level you propose. This is not TRL-
7 or greater.

Foldaway wings aboard rocket launched vehicles have been demonstrated

On a much smaller scale than you propose. This is not TRL-7 or greater.

Inflatable heat shields have been demonstrated.

On a much smaller scale and they were not all completely successful.
This is not TRL-7 or greater.

Airplane towing gliders have been demonstrated

But not snagging a glider in mid flight. You say you've done this with
small aircraft, but even if this is true, the scale is far too small.
This is not TRL-7 or greater.

Recovery of spacecraft by tow planes from orbit have been demonstrated

On a scale which is orders of magnitude smaller than you propose. And
in those cases, the spacecraft was descending under parachute (snagged
by a hook trailing from the tow plane), which isn't the same thing as
snagging a glider. Apples and oranges. This is not TRL-7 or greater.

Parallel staging has been demonstrated

Sure.

Feeding propellant from one parallel staged element to another has
been demonstrated.

No, not in the way you propose. One ET feeding propellant to one
orbiter through one LOX line and one LH2 line is not the same as the
more complex method you propose. This is not TRL-7 or greater.

Jeff
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