Questions tagged [engines]

Questions regarding equipment used to propel a spacecraft or a rocket. Questions about attitude control jets should be tagged "attitude".

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43
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2answers
6k views

Why were the Space Shuttle's main engines placed on the orbiter?

Since the main engines can't be used after external tank separation, what's the reason for having the engines on the orbiter rather than just building a third rocket on the stack instead of the ...
43
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1answer
5k views

How did the Apollo Lunar Module ascent engine prevent gas bubbling through fuel?

As I understand it, in order to keep the lunar module ascent engine simple, instead of fuel and oxidant pumps, tanks of helium at pressure were used. This pressure was used to force the fuel and ...
37
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3answers
12k views

Why are rocket engines operating above 100% often considered nominal?

It was brought to the attention of the community that right before the crash of Antares the commentator noted: "Main engines at 108%" It was noted that other engines were also reported to work at ...
35
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9answers
12k views

Why do rocket nozzles flare?

Why do rocket nozzles open wider at the end than, let's say, get narrower? Let me explain: A jet engine works by having this amazing thing called a combustion chamber. The combustion chamber ignites ...
33
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6answers
10k views

Why aren't air breathing engines used as small first stages?

I am wondering why we don't use jet engines as first stages. Most small rockets, like the Electron, can lift off with a small thrust. In the Electron's case, 192 kN. Why can't we replace the 9 ...
33
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7answers
16k views

Why are Rocket engines at the base of the rocket?

I don't know much about Rockets, but all that I have seen, from the Saturn V to SpaceX's Falcon 9 have the engine at the bottom. Doesn't this make the Rocket really unstable, like balancing a pencil ...
33
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3answers
6k views

Why do the exhaust flames from cryogenic stage engines appear to be separated from the nozzle?

Why do the exhaust flames from cryogenic stage engines appear to be separated from the nozzle?
32
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1answer
5k views

What are the 'lights' inside Shuttle main engines at landing?

I have a night-landing photo of the Shuttle showing lights (I assume some type of glow-plug to burn off extraneous fuel). My understanding is that only the OMS engines burn to begin reentry. Can ...
30
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5answers
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Why does a rocket engine provide more thrust in a vacuum than in atmosphere?

According to NASA Each Space Shuttle Main Engine operates at a liquid oxygen/liquid hydrogen mixture ratio of 6 to 1 to produce a sea level thrust of 179,097 kilograms (375,000 pounds) and ...
29
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3answers
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Why doesn't the US use European rocket engines?

US Companies have been using Russian rocket engines for their rockets for a long time, even during sanctions. But as I was going through the European rocket launches, I felt European rocket engines ...
28
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5answers
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Falcon 9: engines stabilize spin

On CRS-16, the landing Falcon 9 booster entered a spin rotation due to a stalling grid fin hydraulic pump. According to Musk, the engines stabilized the spin. How is this possible? The main engines ...
25
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2answers
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How did the tangential thrusters for the 2014 LDSD test spin-up then spin-down so nicely?

I just watched the NASA JPL video of the 2014 test of the Low-Density Supersonic Decelerator (LDSD). Tangential thrusters are used to spin up the craft for stability before the main rocket ignites. ...
25
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2answers
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What is a thrust puck on Starship?

Elon Musk recently mentioned a Thrust Puck on Twitter, "We’re stripping SN2 to bare minimum to test the thrust puck to dome weld under pressure, first with water, then at cryo." He also mentioned ...
24
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1answer
3k views

What actually is RP-1, and how is it different from any other hydrocarbon liquid fuel?

Related: Russian "kerosene" versus American "RP-1", however that's more about the details of specific rocket kerosene specs than rocket kerosene in the context of hydrocarbon and ...
24
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1answer
6k views

Why is the SABRE engine curved?

Why is the Reaction Engines Limited SABRE (Synergistic Air-Breathing Rocket Engine) curved along it's length?     Illustration of the SABRE engine with the pre-cooler heat ...
24
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1answer
4k views

What makes the Merlin vacuum engine so deeply throttleable?

According to the October 2015 revision of the Falcon 9 User's Guide, the Falcon 9's first stage Merlin 1D engines have a 70%-100% throttle range, while the second stage Merlin 1D Vac engine has a 38.5%...
23
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5answers
6k views

Reasons why liquid anhydrous ammonia fuel chosen for the X-15? Has it been used in other rocket engines?

Both Flight 90 and Flight 91 of the North American X-15 crossed the Kármán line, reaching altitudes of 106.01 and 107.96 km respectively. Both flights were piloted by Joseph A. Walker, who became in ...
22
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4answers
6k views

Why 31 engines for the BFR?

I understand the philosophy of using relatively many smaller engines so that a single engine failure has minimal impact on the mission (provided you can keep the shrapnel from shredding the others) ...
22
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3answers
4k views

Why was the engine of the launch vehicle recently tested in Iran “not a very good missile engine”?

The NPR News item What's Iran Up To With Recent Rocket Launch Attempt? by NPR's Geoff Brumfiel, about a recent launch test in Iran includes the following: Earlier this week, Iran attempted to launch ...
22
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1answer
2k 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 ...
21
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1answer
7k views

How does SpaceX ignite their engines?

Based on the aborted launch on Thanksgiving 2013 of the first Falcon 9 v1.1 from Florida, we know that an issue occurred where oxygen got into the ground based TEA-TEB sources. I understand that TEA-...
20
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1answer
584 views

Does the proximity of engines in engine clusters cause interference?

One way to create a heavy launch vehicle is by clustering large numbers of small engines together in a stage. An example of this approach is the SpaceX Falcon 9: Now I've heard people arguing against ...
19
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3answers
20k views

What are the differences between a standard Merlin engine and the Merlin Vacuum engine?

I know that there's a difference between SpaceX's Falcon 9 1st stage engines and the 2nd stage engine, since that stage is specifically tuned for vacuum. Wikipedia also says that the Merlin Vacuum ...
19
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1answer
7k views

What is so hard about making a throttleable large rocket engine?

In the old days, most rocket engines weren't throttleable. I think the first one was actually the Apollo Lunar Module descent engine. But I'm interested in large, turbopump-fed engines using RP-1/LOX ...
18
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2answers
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Was there an anomaly during SN8's ascent which later led to the crash?

In SpaceX'S video, there is a conflagration inside the engine enclosure which seems irregular at around 1:49:49. The engine far left of the engine camera stops working and a few seconds later some ...
18
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3answers
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What engines did (or could) Buran have?

As I learned the primary design difference between Buran and the USA Space Shuttles was that Buran rode a rocket to the orbit passively, while the Shuttles were firing their own engines, riding on ...
18
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2answers
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Why is TEA-TEB chemical ignition used instead of spark ignition?

Both the Saturn V and the Falcon 9 use TEA-TEB to ignite their kerosene-fueled engines. TEA-TEB is pyrophoric, igniting spontaneously on contact with air. This poses handling issues; it must be stored ...
18
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1answer
2k views

Why the non-symmetric design of rocket nozzles?

Although I have seen many perfectly symmetric nozzles, I have also seen designs such as this (Virgin Galactic) which is only symmetrical about one axis: Why is this?
17
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1answer
10k views

What is the rocket engine chilldown?

In many launch sequences I see the phrase 'engine' chilldown' coming up. What is this and why is it done?
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2answers
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How exactly is the pressure inside the combustion chamber monitored?

Given that temperatures in the combustion chamber are crazy high, are there any pressure sensors rated for the high temperature and high pressures located there? Or is there a cooling mechanism for ...
17
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1answer
464 views

Was Jules Verne the first to propose the retro-rocket concept?

In his novels 'From the Earth to the Moon', and 'Around the Moon', Jules Verne writes about a set of rockets fitted to the spacecraft he imagined, that were intended to be fired in order to slow down ...
16
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3answers
5k views

Were the Space Shuttle's Main Engines ever off while the Solid Rocket Boosters were firing?

I always though the Space Shuttle needed a combination of its solid rocket boosters and its main engines to remain stable while launching. The following diagram found on Wikipedia seems to agree: ...
16
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1answer
692 views

Why is the exhaust plume of Falcon 9 upper stage shaped the way it is?

The (single) Merlin 1D vacuum engine's exhaust plume has a symmetric shape, comprising of six distinct "inner" plumes. Why does it have this shape? Is it due to the shape/configuration of fuel ...
15
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1answer
3k views

Why was the Apollo CM main engine thought to be unreliable on Apollo 13?

When Apollo 13 had most of its internal systems destroyed by an explosion, NASA decided that the best course of action would be to fire the main engine on the dark side of the moon to send the capsule ...
14
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2answers
3k views

Can nuclear thermal engine designs be shutdown in such a way as to be restartable, in space?

Nuclear thermal rocket designs have a working temperature of 2000k or greater. Shutting such a reactor down won't stop that heat production instantly - it'll take quite some time to cool. Do current ...
14
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4answers
4k views

Is LMP-103S truly a viable replacement for Hydrazine?

LMP-103S is the name of a new monopropellant, tested on the PRISMA mission in 2010. It's main ingredient is ADN (Ammonium Dinitramide), a strange chemical invented in the 70's in USSR and ...
14
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1answer
1k views

Can a Soyuz-MS still propel itself back to earth if all its Hydrogen Peroxide decomposed?

In this answer it is stated that: If the fuel fully decomposes then return to Earth is still possible but only via ballistic descent I find it a little bit surprising, but maybe there is enough Δv ...
14
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1answer
1k views

Why aren't expander cycle engines used on lower stages?

Looking at the simplicity of BE-7, I was wondering why dual closed expander cycle engines are not used more commonly and, as far as I know, are not used as lower stage engines at all. A commonly ...
14
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4answers
3k views

Why do pump and pressure fed liquid engines need to operate at high pressures?

There is apparently some confusion as to why pump or pressure fed liquid rocket engines need to operate at high pressure to product significant thrust, based on the comments to this question about ...
13
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4answers
14k views

Why don't rockets drive the turbopump from the combustion chamber?

As I understand it, liquid-fueled rockets typically burn some amount of their fuel in a separate low-pressure combustion chamber, and then use the combustion products produced to drive the turbopump. ...
13
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5answers
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Other than then N-1 (30 engines) has there been a single stage of a rocket with more engines than a Falcon 9?

The Saturn V had 5 engines (F-1) on the first stage, five engines on the second stage (J-2). The N-1 had 30 engines on its first stage (NK-15). The Falcon 9 (1.0 and 1.1) have 9 Merlin 1 engines on ...
13
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1answer
3k views

How do Voyager 1's Trajectory Control Thrusters differ from its Attitude Control Thrusters?

There are several popular news items about the recent test of Voyager 1's Trajectory Control Thrusters to see if they can be used for attitude control to facilitate communication with Earth. The ...
12
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2answers
2k views

Why is there so much variation in the number of engines on launchers?

There is much variation in the number of engines used in the liftoff stage of various launchers. Saturn V had 5 Space shuttles had 5 (3 main + 2 SRB) Falcon 9 has 9 Soyuz has 20 N1 had 30 Delta Heavy ...
12
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1answer
729 views

Why does the core stage of the Ariane 5 produce more thrust in vacuum?

In listening to a youtube video that was discussing the Ariane 5, the narrator noted briefly in passing that the Vulcain 2 engine produced more power thrust in a vacuum than it did at sea level. Not ...
12
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1answer
6k views

How do the Falcon 9 engines re-ignite?

Do they use a tungsten wires or something else?
12
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1answer
724 views

VASIMR - Propellant usage data?

So I am using the VASIMR data of approximately 5N of force per 250kw of power draw. As far as I can see, this scales fairly linearly, so 500kw would result in 10N of force. (Might require two engines, ...
12
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1answer
949 views

Red color in the nozzles of Soyuz-2 rocket engines RD-107 and RD-108, is it only a decoration?

Many pictures of the Soyuz-2 show the inside of the nozzles painted with a brilliant red. Is there any function of the paint during ignition and operation of the rocket engines, or is it just a ...
12
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2answers
2k views

Quality vs. Quantity for Rocket Engines

I read a while ago about the famous Soviet N-1, called by some the most powerful rocket (in terms of thrust at liftoff) in history. It used an incredible 30 engines in its first stage. The American ...
11
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3answers
2k views

What are the phases of ignition (and flameout) of a liquid fuel engine?

As I observed ignition of several rocket engines (Shuttle, AMDE, Lynx Suborbital, Saturn V) they all come through a couple phases - emitting various vapors, unfocused flame, etc, before the proper "...
11
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1answer
3k views

Merlin 1D Engine Throttling

How does the SpaceX Merlin engine control the mass flow rate to throttle its thrust? Do the pintle injectors move? Does the mass flow rate to the gas generator change?

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