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50 votes
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If rocket engines only need fuel and oxidizer, then why there are so many pipe lines on the engines?

While an ideal engine would just ingest fuel and oxidizer and produce exhaust gas real world engines will have some combination of regenerative cooling, film cooling, turbine exhaust, hydraulic power, ...
GremlinWranger's user avatar
34 votes
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In a shuttle launch, what would have happened if all three SSMEs failed during flight?

Much of the time, you would die. Refer to the 3 OUT BLACK ZONE chart from here The heavy black lines show where the situation is not survivable (black zone). Acronymology for the black zone charts: ...
Organic Marble's user avatar
33 votes
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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?

tl;dr Each engine reports a self-test status to the vehicle it's attached to. "MCF" is one of the possible statuses and indicates that the engine controller has detected a serious - but not ...
Organic Marble's user avatar
32 votes
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What (if anything) could have caused all three shuttle main engines to stop at the same time?

There were a few common cause, credible failures. Loss of inlet pressure to the engines due to a leak in the External Tank or failure of the tank pressurization system. (This loss of pressure is ...
Organic Marble's user avatar
29 votes
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Why did the SSMEs gimbal during ignition?

Before the engines started but after the Auxiliary Power Units (which provide hydraulic power) were started, the engines were gimbaled to ensure that the thrust vector control system was working ...
Organic Marble's user avatar
28 votes
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What are the small gas jets at the rims of the Space Shuttle Main Engines?

The lines that exited at the end of the nozzle were drain lines carrying leakage from seals, output of hydraulic actuator drain lines, etc. The following schematic shows the various systems attached ...
Organic Marble's user avatar
25 votes
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How was fuel crossfeed achieved, between the main tank and the Shuttle?

1) Can someone provide an overview of the crossfeed system - in particular the detachable joint that fed LOX to to the shuttle from the tank? The buzzwords to use for googling this topic are "ET ...
Organic Marble's user avatar
20 votes
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Which STS mission raised the normal engine throttle above 100%, and what change to the SSME made that possible?

tl;dr The first mission to run the engines normally at above 100% of nominal maximum thrust: STS-6 The changes to the engine made that thrust increase possible: the 147 design changes implemented ...
Organic Marble's user avatar
20 votes
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From which NASA publication originates/where can I find a higher resolution version of this SSME flow diagram?

It's on pdf pages 139-141 here: https://gandalfddi.z19.web.core.windows.net/Shuttle/SSME_MPS_Info/KSC-SSME_System_Eng_Handbook.pdf but you'll have to "glue" it together into one drawing. ...
Organic Marble's user avatar
19 votes
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What does "in the bucket" mean?

The space shuttle throttled down its main engines from the normal setting of approximately 104% to around 67% as it was passing through the region of max dynamic pressure ("max q"), to make sure that ...
Organic Marble's user avatar
18 votes

Why is SpaceX's Raptor's design so simple in comparison to SSME?

I wouldn't draw any conclusions based on diagrams alone, SSME is very well-known to the public, so we have a more detailed diagram. That doesn't mean that the actual engine is more or less complex, ...
JohnEye's user avatar
  • 1,336
18 votes

How was fuel crossfeed achieved, between the main tank and the Shuttle?

The crossfeed seen in KSP works by pumping fuel from one fuel tank to another, i.e. against tank pressure. To do this, you need pumps (independent of the engine turbopumps). Pumping large amounts of ...
Hobbes's user avatar
  • 128k
16 votes
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Two-Stage Fully-Reusable Shuttle

There were literally dozens of different designs proposed. Page 100 of the referenced book lists more than fifty different designs, and then there are 7 pages showing thumbnail sketches of them. Here ...
Organic Marble's user avatar
15 votes

Why is SpaceX's Raptor's design so simple in comparison to SSME?

A lot of questions here, let's tackle these two first: 4.And last but not least, what's SpaceX's solution for the oxygen-rich environment at 377bar, 748K injector and 546bar, 811K pre-burner? 2.The ...
Level River St's user avatar
12 votes

How long did it take to remove or install an SSME on the Space Shuttle?

In the Orbiter Processing Facility (orbiter horizontal) it took, at the end of the program, "less than 4 hours" to install all three engines1. There's the Orbiter, Go Put a Motor in It Good pictures ...
Organic Marble's user avatar
12 votes

What is the area of the SSME nozzle knowing only thrust at sea level and in vacuum?

You can use the method I explained at the start of this answer: Falcon 9 Merlin 1d thrust calculated through every moment of flight Quoting from that, you use the thrust equation: $ \ \ \ F = \dot{m}_\...
Organic Marble's user avatar
12 votes
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SSME/RS-25: why seal between LOX pump and preburner?

Really, there's a whole lot of aspects that make your proposed setup less reliable than desired: The laws of physics have no knowledge of how to run a preburner at exactly the right mixture ratio at ...
TooTea's user avatar
  • 1,765
11 votes
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RS-25 Hot Fire Test

The engine controller is a computer mounted on the SSME which monitors and controls the engine. It, for example, takes throttle commands as a % of power level from the vehicle and translates them ...
Organic Marble's user avatar
11 votes
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STS: How much thrust did the nominal post-MECO LOX dump produce?

Please refer to this (modified) schematic diagram from the crew's Ascent Pocket Checklist for this discussion. The blue shows the parts of the plumbing still filled with LOX after MECO. The green is ...
Organic Marble's user avatar
11 votes
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Why isn't NASA planning on saving some of the RS-25Ds due to their historical significance?

Many SSMEs are already displayed in museums. Stafford Air and Space Museum (theirs is taken apart and you can look in the pieces, very cool) Stennis Space Center National Air and Space Museum Space ...
Organic Marble's user avatar
10 votes
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What is the purpose of the "shaft" and "block" in these two different engine gimbal joints?

Let's take the second image for the F1 engine - the situation is similar for SSME, though everything is 'upside-down' in its pictures. The 'seat', 'body' and 'block' are three parts that turn against ...
SF.'s user avatar
  • 55k
10 votes
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What is the job of the acoustic cavities inside the main combustion chamber?

They are provided to help damp out combustion instabilities. The main injector uses cooled baffle elements, developed at Glenn in the 1960s to control pressure waves that could destroy the engine....
Organic Marble's user avatar
9 votes
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Theoretical Max G forces on Shuttle Launch?

Stealing the mass-at-MECO number from this answer, and using the 104.5% thrust numbers for 3 SSMEs from here, I get (3 x (490,000) lbf / 308650 lbm ) = ~ 4.75 g's Sanity check (3 x (.65 x 490,000) ...
Organic Marble's user avatar
8 votes
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Which RS-25s are on the Artemis 1 rocket?

Building on the information found in my answer to this question (which answers part of the question above "Is there a listing of which SSMEs are planned for each Artemis flight" and gives ...
Organic Marble's user avatar
7 votes
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How much fuel/oxidizer was held in the piping of the Shuttle orbiter?

There are reasons why this wouldn't have worked at all. I'll explain at the end, but first the numbers you ask for. Liquid mass in Orbiter plumbing: Common feedline (between external tank disconnect ...
Organic Marble's user avatar
7 votes
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Disposal pool during RS-25 engine test?

The containment pond at the Stennis Space center, Test Stand A-1, is used to hold runoff from contact-cooling water (where water comes into contact with something other than the insides of a clean ...
Rob's user avatar
  • 3,276
7 votes

Why was the reusability of the SSMEs so poor, and why was this considered acceptable given their purpose to launch a reusable vehicle?

No Space Shuttle questions are simple, since it was a long program with many different drives beyond engineering perfection*, so the short answer is 'yes, given money, time and perfect management/...
GremlinWranger's user avatar
7 votes
Accepted

RS-25E cost estimate but sentence confusing (approximately: help; maybe)?

the recurring cost per engine set (five RS-25E versus four RS-68B) would be significantly more (approximately 90 percent per engine; approximately $165M per flight set) for the SSME derivative. Hey, ...
Russell Borogove's user avatar
6 votes
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Space Shuttle and SSME Servicing Procedures for Re-Launch

It varied throughout the program - the SSMEs changed a lot over its course. Columbia's original FMOF engines were only marginally OK for flight. Until the Pratt turbopump redesign, the high pressure ...
Organic Marble's user avatar
6 votes
Accepted

Is it possible to estimate the nozzle characteristics of the Rocketdyne HG3 engine?

Here is a mathematical answer to your question. Using the numbers you provided for the HG-3, we have, $$I_{sp} = 451 \ \text{s} \ (\text{vac})$$ $$F = 1,400,745 \ \text{N} \ \ (314,900 \ \text{lbf}) \...
TRF's user avatar
  • 449

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