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48

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, ignition systems, pressure sensing, tank pressurization systems, drain/purge/test lines, and electrical connections that just look like pipes for heat ...


34

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: alpha = Angle of attack ALT = Altitude c.g. = Center of gravity EAS = Equivalent Air Speed MECO = Main Engine Cutoff MM602 - Major Mode 602, the onboard ...


34

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 catastrophic - failure within the engine. Details The Space Shuttle Main Engines (SSMEs) aka RS-25s transmit data to the vehicle they are attached to using a ...


32

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. The propellant feedlines were not identical in shape and this resulted in some minor performance differences. For example, the left SSME LH2 line had a ...


32

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 what caused all three engines to shut down during the Challenger accident, when the External Tank ruptured) Engine operation was normal until the fuel ...


29

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 properly. At T minus 4 minutes, the fuel system purge begins. It is followed at T minus 3 minutes 25 seconds by the beginning of the engine gimbal tests, ...


28

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 to these drain lines. Source: Rockwell SSME Pocket Data Book, R/RD87-142. This graphic differentiates between the transfer ducts (which carried the hydrogen ...


24

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 Umbilical". The system as implemented on Shuttle was complicated but caused major problems only once in the program (see below). There were two umbilical areas ...


19

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 between the FMOF and FPL versions of the SSME. Details The SSME had five major versions over the life of the program. The definition of 100% Rated Power Level ...


18

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 the certified dynamic pressure limit was not exceeded. Once the threat had passed, the engines throttled back up. If you plotted throttle level vs time on a ...


17

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 fuel quickly is not easy. You need to stop pumping cleanly when the tank is empty (or risk a pump explosion when the pump runs dry), this is difficult: you ...


17

I wouldn't recommend it, and there's several reasons why. First, even if we assumed you'd get chemically pure water out of the exhaust plume, in essence distilled water, it would lack any dissolved minerals and cause you to lose electrolytes. If that was all that was wrong with it, then small quantities wouldn't hurt you, but you'd have to substitute lost ...


17

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, because many things are omitted from diagrams. To prove my point, here is a newer Raptor diagram drawn by a propulsion engineer Elisei Maslov, who's ...


13

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 Raptor's oxygen pump sits directly on top of the main combustion chamber, while the SSME's two pumps are on the opposite sides of the main combustion chamber. ...


12

They do use sparklers: the Radially Outward Firing Initiators (ROFI), derived from the Shuttle system, are started at T-15 seconds. Note that a hydrogen fire is the expected result of this system; they just didn't expect it to be this extensive. On the NasaSpaceflight forum, someone suggested that the scorching of the insulation is caused by the hydrogen not ...


12

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 engine 2054 on OV-105 Endeavour If you really want to know which engine flew where, there's a chart that tracks the flight history of each engine. Engine ...


12

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 here On the pad, it took longer, 3 or 4 days, at least in 1999. "Shuttle engines have been changed on the launchpad several times in the past and generally it ...


11

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 into control commands for the engine valve control loops. The SLS engine controller is a new hardware device and presumably new software as well. The pogo ...


11

The biggest risk I foresee is nitric acid. A hot open flame in the atmosphere will cause N2 and O2 to react, creating a number of different molecules such as NO and NO2. These dissolve reasonably well in water and will form acids.


11

The SSME is a staged-combustion rocket engine, which means that some small fraction of the propellant flow into the main combustion chamber is first diverted into a small pre-burner (two actually). These preburners combust (relatively) small amounts of fuel and oxidizer to produce hot exhaust gas which is expanded through a turbine, which is mechanically ...


10

This is complicated, but here is the gist: Thrust is generated by flowing high pressure gas into a lower pressure environment. This flow is supersonic, so what goes on downstream of the throat (top of the the nozzle) cannot be sensed by what is going on in the combustion chamber (sound is just a pressure wave). The nozzle is supersonic, the combustion ...


10

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 with a cheaper, expendable version, currently designated the RS-25E ('E' for expendable). This engine may be based on one or both of two single-use ...


10

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 is anything but a simple, or even 'old' engine. Its re-manufacture would likely benefit from modern techniques, like the people examining starting F-1 engine ...


10

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 the helium pressurization line. Two minutes after MECO the onboard computers start the dump by opening the LO2 Manifold Pressurization Valve (1), the LO2 ...


10

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 each other. The block can turn around the shaft in X axis. The body can turn around the block in the Y axis. The Z axis remains fixed, as the block can't ...


10

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. Pressure waves in the space shuttle main engine combustion chamber are also controlled by acoustic cavities. Testing by Glenn engineers determined the ...


9

The SRB's were ground tested, as were the SSME's. Consider for a moment the scale/scope of a test stand that can hold an SRB full fire test. (The SRB's put out 2.8 million lbs of thrust. To compare, even an F-1 engine was only 1.5 Mlbs). Ironically the only real standalone launch of an SRB was the Ares-1X launch, well after the Shuttle was ready to be ...


9

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) lbf / 308650 lbm ) = ~ 3.1 g's Using the approximate 65% power level at shutdown, assuming that the thrust varies linearly with throttle percent (and ignoring ...


8

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 this image) Where are the lost RS-25D Block 2 engines? the history of the 4 engines on the first SLS booster is Engine / Shuttle Missions 2060: 127, 131, 135 ...


7

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 pipe). You can see it's not particularly deep and does not itself runoff or drain anywhere (except to groundwater and the nearby river). Google Map view of the ...


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