Hot answers tagged

50 votes
Accepted

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, ...
34 votes
Accepted

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: ...
34 votes
Accepted

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 ...
32 votes
Accepted

Was the third shuttle engine any different from the others?

The engines themselves were identical within manufacturing tolerances, but there were some installation differences, mostly due to "packaging" constraints in the crowded aft compartment of the shuttle....
32 votes
Accepted

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 ...
29 votes
Accepted

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 ...
28 votes
Accepted

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 ...
25 votes
Accepted

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 ...
20 votes
Accepted

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 ...
20 votes
Accepted

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. ...
19 votes
Accepted

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 ...
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 ...
  • 122k
17 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, ...
  • 1,296
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 ...
15 votes
Accepted

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 ...
12 votes

Was the third shuttle engine any different from the others?

The 3 engines were identical. Of the 46 SSME engines produced, at least 3 were installed in 3 different positions on various flights: engine 2012 on OV-103 Discovery engine 2019 on OV-104 Atlantis ...
  • 122k
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 ...
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}_\...
11 votes
Accepted

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 ...
11 votes
Accepted

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 ...
10 votes
Accepted

How will the SLS first stage be supplied with engines? Copy manufacturing the RS-25 or replacing it?

Some changes appear to be under consideration for future production of SLS RS-25s: From Wikipedia's SSME page, about the SLS plan: Once the remaining RS-25Ds are used up, they are to be replaced ...
10 votes

How will the SLS first stage be supplied with engines? Copy manufacturing the RS-25 or replacing it?

Engines at the size and performance of an SSME are very difficult to develop. The SSME has one of the highest ISP's ever attained in a production engine. (Not some crazy Fluorine involving demo). It ...
  • 77.5k
10 votes
Accepted

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 ...
  • 53.4k
10 votes
Accepted

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 ...
10 votes
Accepted

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....
9 votes
Accepted

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) ...
8 votes
Accepted

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 ...
7 votes
Accepted

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 ...
  • 3,236
7 votes
Accepted

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 ...
7 votes
Accepted

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 ...

Only top scored, non community-wiki answers of a minimum length are eligible