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Questions tagged [ssme]

SSME is the acronym for the Space Shuttle Main Engine. Sometimes called the RS-25, or RS-25D.

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Which STS mission raised the normal engine throttle above 100%, and what change to the SSME made that possible?

As indirectly stated in an answer to How long does Max-Q last?, during later Space Shuttle launches the main engines were operating at above 100% of their nominal maximum thrust. Specifically from ...
user's user avatar
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21 votes
3 answers
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How was fuel crossfeed achieved, between the main tank and the Shuttle?

Whenever a fan of Kerbal Space Program mentions the super-efficient 'asparagus staging' in any professional context, the automatic response is 'That won't work. KSP fuel pipes are pure magic.' The ...
SF.'s user avatar
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21 votes
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Why not use Sparklers on Delta-4 Heavy launches to burn off the hydrogen?

With three CBC (Common Booster Core) modules firing their RS-68A engines simultaneously, a Delta 4 Heavy launch is an impressive sight. The RS-68 is a LOX/LH2 engine. As part of the launch sequence, ...
geoffc's user avatar
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17 votes
1 answer
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What does "in the bucket" mean?

I've heard this expression a couple of times before. It seems related to the engines, but I can't find any information on it, except in the context of testing them. Here's two videos where it occurs: ...
loopbackbee's user avatar
10 votes
1 answer
533 views

STS: How much thrust did the nominal post-MECO LOX dump produce?

Following up to some questions asked in comments to the answer to this question: With pressure-fed engines, is any measurable thrust generated by venting the pressurant out the engine bell after ...
Organic Marble's user avatar
23 votes
1 answer
3k views

What are the small gas jets at the rims of the Space Shuttle Main Engines?

As can be seen in close-up footage of SSME ignition, such as the video below, there are small jets of an unknown gas/vapor emanating from specific points around the ...
dgw's user avatar
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18 votes
1 answer
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In a shuttle launch, what would have happened if all three SSMEs failed during flight?

I'm certain there are several flight regimes where this could happen, and that the procedures should be different for each one. For instance, this is a very different question before lift off than it ...
Michael Stachowsky's user avatar
11 votes
2 answers
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Have SRBs or SSMEs ever launched without a space shuttle?

It seems to me that the April 12, 1981 launch of Columbia (STS-1) was the manned spaceflight with the most untested hardware of any manned space launch. Even the Vostok and Mercury launch systems had ...
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4 votes
5 answers
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Space Shuttle and SSME Servicing Procedures for Re-Launch

There's been a lot of discussion about SpaceX's ~30% price reduction from re-use of the first stage, which got me to wondering: why exactly was the Space Shuttle so expensive to service and prep for ...
TheRadicalModerate's user avatar
1 vote
2 answers
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How does the Space Shuttle's SSME engine's thrust vary after ignition?

After writing the question Do Blue Origin's BE-3 engines need to run for 7 seconds to “warm up”?, I took a look at the YouTube video SSME ignition sequence (found in What are the small gas jets at the ...
uhoh's user avatar
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What is a "Major Component Failure" referred to in news reports about the unsuccessful Space Launch System core stage test firing?

In reporting about the unsuccessful green run of the SLS core stage, Ars Technica mentions About 50 seconds into what was supposed to be an 8-minute test firing, the flight control center called out, ...
Organic Marble's user avatar
17 votes
3 answers
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In a cryogenic fuel rocket, at what pressure is the fuel injected into the engine?

The pressure in the Space Shuttle's main engines must be very high to get the vehicle off the ground (with the SRB assist, of course). With such high pressures inside the engine, how do you inject ...
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16 votes
1 answer
2k views

Why did the SSMEs gimbal during ignition?

During Shuttle ignition sequence: the engines always slightly gimbal closer together as they reach full combustion (I'm guessing, from the plume appearance). Why?
Anton Hengst's user avatar
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NASA's RS-25 Engines

I am developing a FSX-based space flight simulator FSX SpacePort. I've been trying to get the detailed specs on NASA's RS-25 engine, namely, what were the ramp-up times for this engine? As in, how ...
Mitch99's user avatar
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4 votes
1 answer
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Actuators for gimbaling of engine in rockets and launch vehicles

For controlling the rockets to stay on course, continuous engine control is require which is done by using gimbal actuators. What type of gimbal actuators have been used on SSME, Rocketlab's ...
Amar's user avatar
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22 votes
2 answers
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Can I drink the water from the plumes of SSME?

Shuttle's SSME uses cryogenic Hydrogen(LHX) and Oxygen(LOX) as their propellent to give hot water vapour. If I somehow manage to get the exhaust plume and condense it to liquid, Can I drink it ...
Hash's user avatar
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19 votes
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Was the third shuttle engine any different from the others?

The space shuttle used three SSME, organized in a triangle with two next to each other closest to the external tank, and one on top of those. I am pretty sure the first two engines were close to ...
SE - stop firing the good guys's user avatar
11 votes
1 answer
778 views

Why don't all SSME turbopumps gimbal with the engine?

The SSME low-pressure pumps (both fuel and oxidizer) are mounted to the vehicle structure and don't gimbal. The high-pressure pumps are gimbaling with the engine, so the propellant lines between low-...
mpv's user avatar
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11 votes
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From which NASA publication originates/where can I find a higher resolution version of this SSME flow diagram?

This came up when I was taking a look at Endeavour over in LA. Where can I find a readable version of this full flow diagram (valves, control systems, and everything)?
Anton Hengst's user avatar
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8 votes
2 answers
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SSME propellant duct routing

The low pressure propellant ducts in SSME are routed around the engine in a somewhat complicated way. Both fuel and oxidizer lines leave the low-pressure turbopump, go around, down and then turn back ...
mpv's user avatar
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8 votes
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What is the job of the acoustic cavities inside the main combustion chamber?

I am new to rocket engines. I was looking at an image of RS-25 engine's MCC and found these acoustic cavities, and I want to know how they work. Can somebody please explain their working principle? ...
Aungmyintmyat Hane's user avatar
6 votes
1 answer
3k views

Theoretical Max G forces on Shuttle Launch?

Reading this question Why are rocket engines operating above 100% often considered nominal? leads me to a question about throttling back the SSMEs in the later stages of a Shuttle Launch to limit G ...
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5 votes
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Why were the SSMEs so much more fragile than the J-2 engines?

This answer mentions that the J-2 engines used by the Saturn V's second and third stages were substantially more resilient than the "extremely complex and sensitive" Space Shuttle main engines. What ...
DylanSp's user avatar
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4 votes
1 answer
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Why isn't NASA planning on saving some of the RS-25Ds due to their historical significance?

A while ago, Scott Manley made a video about the Artemis program and how NASA will expend all its Block II RS-25D engines through the SLS's first four launches. Why isn't NASA planning on putting some ...
WarpPrime's user avatar
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3 votes
2 answers
277 views

From which NASA publication originates/where can I find the color version of this SSME flow diagram?

Sorry to ask such a similar question as the last one, but I already marked that one as answered. My friend who works at the Endeavour exhibit in LA found this diagram left on the ground after a ...
Anton Hengst's user avatar
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3 votes
1 answer
288 views

How would the STS have differed if it used J-2's as the main engine?

In the spirit of counterfactual rocket design questions such as this one - how would the STS have differed from its actual design if it used J-2's as the main engine? What would be the loss in payload ...
DylanSp's user avatar
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3 votes
1 answer
435 views

How much fuel/oxidizer was held in the piping of the Shuttle orbiter?

The space shuttle main engines were in the orbiter portion of the vehicle, but fed fuel (LH2) and oxidizer (LOX) from the external tank. Suppose the external tank is ejected before the LH2 and LOX ...
DrSheldon's user avatar
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1 vote
1 answer
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Shuttle main engines RS-25 refurbishment/material damage

There was some thread here on Space Stack-Exchange about RS-25 refurbishment, but I am interested now, how this refurbishment look from the point of material damage of SSME hardware. In the early ...
bigbang's user avatar
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