could J-2 operate from sea level?

I seem to recall that once upon a time NASA considered using J-2s on the
Shuttle Orbiter. Would this engine have operated effectively from sea level
w/out major modifications?

Mr Jim

On 20 Jul, 06:19, "Mr Jim" wrote:
I seem to recall that once upon a time NASA considered using J-2s on the
Shuttle Orbiter. Would this engine have operated effectively from sea level
w/out major modifications?

The major problem in using a standard J-2 or J-2S at sea level would
have been the low pressure of the exhaust as it left the nozzle. The
exit pressure could have been raised to a value closure to one
atmosphere simply by shortening the nozzle.

On Jul 20, 4:14 am, Proponent wrote:
On 20 Jul, 06:19, "Mr Jim" wrote:

I seem to recall that once upon a time NASA considered using J-2s on the
Shuttle Orbiter. Would this engine have operated effectively from sea level
w/out major modifications?

The major problem in using a standard J-2 or J-2S at sea level would
have been the low pressure of the exhaust as it left the nozzle. The
exit pressure could have been raised to a value closure to one
atmosphere simply by shortening the nozzle.

Remember that they ran full sage tests on the S-11 stage at the
Mississippi Test Facility. All five J-2s running full duration, The
footage is on the Spacecraf Films "Saturn V" DVD.
Theoretically, a J-2 could have an different nozzle engineered for
optimal efficiency at sea level and in lower atmosphere.

SSMEs were originally tested with sea-level nozzles installed.

Matthew Ota

Proponent wrote:

The major problem in using a standard J-2 or J-2S at sea level would
have been the low pressure of the exhaust as it left the nozzle. The
exit pressure could have been raised to a value closure to one
atmosphere simply by shortening the nozzle.


I remember the first version having J-2s also; I think this was NASA
getting its foot in the door with the old "Off The Shelf Parts"
argument* knowing full well it was going to develop a new engine for it.

*My favorite is still the Gemini hatch on the Skylab.

Pat

On Jul 20, 12:19 am, "Mr Jim" wrote:
I seem to recall that once upon a time NASA considered using J-2s on the
Shuttle Orbiter. Would this engine have operated effectively from sea level
w/out major modifications?

Mr Jim

How about an airstart SSME? Could the ISP have been increased if NASA
had gone forward with and airstart SSME?

Danny Deger

Pat Flannery wrote:


I remember the first version having J-2s also; I think this was NASA
getting its foot in the door with the old "Off The Shelf Parts"
argument* knowing full well it was going to develop a new engine for it.

*My favorite is still the Gemini hatch on the Skylab.

Pat

"Gemini hatch on the Skylab"? I'm not familiar with that story. It
sounds interesting. Could you elaborate?

Thanks,

JC

John Crichton wrote:
Pat Flannery wrote:


I remember the first version having J-2s also; I think this was NASA
getting its foot in the door with the old "Off The Shelf Parts"
argument* knowing full well it was going to develop a new engine for it.

*My favorite is still the Gemini hatch on the Skylab.

Pat

"Gemini hatch on the Skylab"? I'm not familiar with that story. It
sounds interesting. Could you elaborate?

For a really good aspect of the story, see

Contingency EVA on Skylab
http://ntrs.nasa.gov/archive/nasa/ca...1979072704.pdf


--
Dave Michelson

John Crichton wrote:

"Gemini hatch on the Skylab"? I'm not familiar with that story. It
sounds interesting. Could you elaborate?



OM is the whiz kid on this; to save money they used a Gemini hatch for
the EVA airlock hatch on Skylab.
This looked really odd, as the airlock was cylindrical, but the hatch
was designed to fit the truncated cone shape of the Gemini.
It's hard to find good photographic images of it; you can get a look at
it in this cutaway: http://history.nasa.gov/diagrams/sk009.gif
Back when it first got designed, Skylab was going to use quite a few
off-the-shelf parts, including having the telescope/solar array mount
based on a LM, but as the project evolved and they realized that they
could launch a lot more involved lab using the Saturn V, that got
changed also.

Pat

Pat Flannery wrote:


John Crichton wrote:

"Gemini hatch on the Skylab"? I'm not familiar with that story. It
sounds interesting. Could you elaborate?



OM is the whiz kid on this; to save money they used a Gemini hatch for
the EVA airlock hatch on Skylab.
This looked really odd, as the airlock was cylindrical, but the hatch
was designed to fit the truncated cone shape of the Gemini.
It's hard to find good photographic images of it; you can get a look at
it in this cutaway: http://history.nasa.gov/diagrams/sk009.gif
Back when it first got designed, Skylab was going to use quite a few
off-the-shelf parts, including having the telescope/solar array mount
based on a LM, but as the project evolved and they realized that they
could launch a lot more involved lab using the Saturn V, that got
changed also.

Pat

Would the "Gemini" hatch be the one labeled "EVA Hatch" in the cutaway
drawing?

Thanks,

John Crichton wrote:

Would the "Gemini" hatch be the one labeled "EVA Hatch" in the cutaway
drawing?

Yup, that's it.
Here's (finally) a decent photo of it:
http://history.nasa.gov/EP-107/p75.htm

Pat