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Questions tagged [liquid-fuel]

Questions regarding rocket propellant in liquid form, the main type used for chemical rockets.

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Solid hydrogen hybrid motor engine for launch?

Would hydrogen unlike water in a solid state take less space or be more stable? How would a rocket work using a block of melting solid hydrogen instead of liquid hydrogen? Has and could any kind of ...
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3answers
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Is it bad if hydrazine freezes on a spacecraft? Is it always kept as liquid, or can it be safely allowed to freeze and then thawed when needed?

After having read this answer I wondered what happens if hydrazine freezes. It looks like it is "normal" and not like water, in the sense that it contracts when freezing, unlike water which expands ...
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How will Robotic Refueling Mission-3's liquid methane tank remain full for six months without any boil off?

Space.com's Lasers, Crystals and 36,000 Worms Will Ride a SpaceX Dragon to Space Station says: To fly on those journeys, astronauts might have to someday harvest fuel from the surface of the moon ...
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1answer
127 views

What liquids last the longest in space?

I am trying to find something that is somewhat stable as a liquid in space. What happens to various liquid elements and compounds in a vacuum? Is there a list or table of the effects of local space ...
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Why doesn't a regeneratively cooled engine crack due to differential expansion induced by thermal gradients?

A liquid rocket engine with regeneratively cooled chamber walls and nozzles would definitely be one among those components experiencing the steepest thermal gradients (Chamber wall inner - $3000 K$ ...
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2answers
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Why are LOx plumbing not insulated?(ref: Huzel and Huang)

In the book Modern Engineering for Design of Liquid Propellant Rocket Engines, the following excerpt appear in chapter 9 - Interconnecting Components and Mounts: The liquid-oxygen lines were not ...
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2answers
112 views

Other than He and N as pressurizing gases

To pressurize the liquid propellant tanks Helium is most widely used and after that Nitrogen. Helium is quite costly and Nitrogen is economic but it messes with the O/F ratio of the engine (ref). So, ...
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How are the liquid propellant umbilical cord protected from the exhaust?

The launch pad umbilical cords supply propellant to the rocket, and will definitely have some remaining at the time of liftoff. I remember the Saturn V footage wherein a heavy protection door slams ...
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1answer
890 views

Why is a purging process necessary for static firing test of liquid rocket engines?

In Chapter 7 of Modern Engineering for Design of Liquid propellant Rocket Engines by Huzel and Huang, mentions the following engine cut off procedure. The cutoff sequence usually consists of ...
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0answers
36 views

Effect of the location of igniter in starting liquid rocket engine

What will be the effect of off axis igniter, say a Spark igniter has to be used along with a pintle? Will the igniter being off axis have any effect on engine start? Also, will an off-center igniter ...
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1answer
213 views

Why are 22N and 440N liquid engines quite common?

One can often spot that liquid apogee engines are 440 N and attitude control systems are 22 N. Is there a reason why the thrusts are proportional? If the engines are scaled for reducing development ...
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2answers
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Challenges of using propyne (aka methylacetylene) as rocket fuel

Propyne is a light hydrocarbon which packs quite a lot of energy in a triple carbon bound. It poses no significant health or explosion hazard by itself, and some European studies have found it to be a ...
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Liquid propellant stored as solid

Some propellants have wildly different melting points. The most extreme case is the theoretically fantastic (and nightmarish in practice) Fluorine-Lithium-Hydrogen tripropellant, with liquid hydrogen ...
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1answer
274 views

How does SpaceX plan to deal with boiloff on the trip to Mars?

Both BFR booster and BFS are to run on Raptor engines, fueled with liquid methane and liquid oxygen - cryofuels. The trip to Mars will take at least a couple months, and BFS requires fuel for powered ...
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1answer
862 views

What is the advantage of using Helium over Nitrogen when used for pressurising LOx?

In this Twitter post of the plumbing line diagram(left half) by LauncherSpace, one can notice that Helium is used for pressurising LOx while Nitrogen is used for pressurising Kerosene. Why the ...
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0answers
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Do rocket labs store propellants at higher pressure than the other rockets?

It is known that the Rutherford engines run on an electric pump-fed cycle. There must be a trade-off between the tank pressure of the electron rocket and battery capacity, for batteries are dead ...
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How to overcome the challenge of igniting kerosene using spark plugs?

Discussions in this question and its answer, concerning the use of spark plug ignition for Kero/GOx system outlines the energy limitations of spark plugs to ignite the mixture. But Ignition Transient ...
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1answer
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Does kerosene get ignited by a spark plug? [duplicate]

Are spark plugs used in kero-LOx engine(say J1 engines)? If so, then there are two major issues when using spark plug to ignite kerosene. Wetting of the spark plug causes spark to be smaller and the ...
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1answer
136 views

How do they know how much liquid propellant is in a rocket just before launch?

In this answer I wrote: In other words, a few tons here or there could depend on something as simple as the weather, or trying to squeeze a little extra propellant in for a given mission with a ...
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1answer
81 views

What parameters of an rocket engine determines whether it is fit for any more static hot fire test?

Typically engines built are repeatedly hot fired to analyses their performance. In between tests, what are the review that the engine undergoes? How is an engine gauged suitable for a hot fire ...
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3answers
1k views

Impact of tidal forces to a liquid in a half-full tank

The german Wikipedia article about tidal forces contains a sentence which mentions, that tidal forces have an impact to an half-full fuel tank: Wo keine mechanisch feste Verbindung besteht, können ...
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1answer
235 views

Which is the preferred mode of liquid rocket engine cutoff - fuel lean cutoff or fuel rich cutoff?

When a bi-propellant liquid rocket engine receives a command to shut down, will the fuel gets cut off first and then the oxidiser - a fuel lean cutoff? Will the oxidiser gets cut off first and then ...
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1answer
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What is advantage of independent pumps vs common pump in clustered configuration?

The images of the engine clustering in the Rocket Labs's Electron rocket gives an indication that there are independent drive pumps for individual engines; I am not sure of it. I am not aware of the ...
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Pressure queries on turbopumps

In the turbopump used in liquid rockets, the stagnation pressure rise is definite. But then the question comes: Whether static pressure rises or dynamic pressure rises or both rises? If both rises ...
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1answer
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What is the surrogate liquid for LOx during the preliminary testing of injectors?

Before transitioning to the LOx tests during any new injector development, water is typically used for calculating flow rates, pressure loss, etc. But testing with water cannot qualify as a suitable ...
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1answer
578 views

What was the reason to use different fuel for the Apollo Service Module propulsion system and reaction control system?

The Apollo Lunar Module LM used the same fuel/oxidizer combination (Aerozine 50 fuel / nitrogen tetroxide (N2O4) oxidizer) for both descent and ascent stage engines and reaction control system. This ...
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3answers
509 views

Can we use liquid propellants in amateur rockets?

Is it possible and worth it to use liquid propellants like liquid oxygen and liquid hydrogen in amateur rockets? What are the other types of liquid fuel used?
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If LOX/LH2 were used in a fuel cell powering an ion engine could it provide a greater delta-v than with a conventional engine?

Question: If LOX/LH2 were used in a fuel cell powering an ion engine could it provide a greater delta-v than with a conventional engine? Conditions: Start in space in a stable heliocentric orbit (no ...
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1answer
62 views

How to calculate mass of fuel for Venus Orbiter

I'm working on a hypothetical constellation of orbiters at Venus for a school project, and I am currently trying to figure out how much fuel I need in the transfer stage. I have already calculated ...
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2answers
198 views

Pro/cons of burning propellant in stochiometric ratio?

Several questions and answers here speak of stochiometric ratio. I do understand it is convinient for efficiency (greater ISP). I also read somewhere (I am unable ro find again the reference, it was ...
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1answer
81 views

If anything, what can cause a rocket engine to flame out prematurely?

I would assume that dropping flow rates or a drop in chamber pressure would cause the engine to stop thrusting, but I am unaware as to what specifically these conditions might be.
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0answers
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Trade-offs in developing larger engines vs using more smaller engines

Looking to explore the inverse point of this question: What challenges are there for more, smaller liquid fuel engines instead of one large? As stated in the answer to the above question, fewer, ...
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Problems with the “How to Design, Build and Test Small Liquid-Fuel Rocket Engines” text

For those that have read or consulted the text: How to Design, Build and Test Small Liquid-Fuel Rocket Engines (Rocketlab/China Lake). Otherwise, see steps 10-13 here: https://risacher.org/rocket/...
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135 views

Why aren't injector pumps used in rockets?

Is there something that makes injectors unsuitable as oxidizer pumps? Seems to me that rockets would benefit significantly from a pump with no moving parts that runs off its own exhaust.
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1answer
278 views

ULA's plan for LH2/LOX 2nd stage that can maintain propellant for an extended period of time?

Business Insider's (long) article SpaceX's biggest rival has a 'genius' plan to cut its rocket launch costs more than 70% contains the statements sourced from ULA's CEO Tory Bruno: Vulcan should ...
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2answers
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Is there a chemical propellant combination with Isp between Methalox and Hydrolox?

Methalox rocket engines (Liquid Methane and Liquid Oxygen) have theoretical specific impulse in the high 300's. Hydrolox rocket engines (Liquid Hydrogen and Liquid Oxygen) have theoretical specific ...
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4answers
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Modern ambient temperature rocket fuel?

This question is in regard to rocket propellants that are liquid at room temperature & pressure (not solid fuel, and not liquid hydrogen liquid oxygen, both of which would be gasses at STP). It'...
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1answer
98 views

An program that automatically generates a rocket guidance system?

This is for a liquid propelled rocket that launches from earth. It could also perhaps be used for orbital maneuvers and landing on the Moon (not mars or earth). The inputs for such a program would ...
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0answers
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How do current reusable boosters create fuel pressure for retro-burn? [duplicate]

For the SpaceX launches of the Falcon9 and Falcon Heavy, and also Blue Origin launch vehicles, the booster stage lands with a controlled decent and firing of main engines for retro-thrust. During ...
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0answers
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Does LOx stay as liquid when entering combustion chamber?

Given the heat from combustion and increased temperature, would the LOx still be in liquid form after emanating from the injector? Or will it instantly transform into gas? Are injectors cooled using ...
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2answers
2k views

How do rockets keep their fuel in a liquid state?

What are some of the measures engineers would take to ensure that the LOX and other similar fuels are kept below their boiling point during flight?
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1answer
174 views

Don't Preburner exhaust fumes disturb the combustion in a Full-flow Staged Engine?

Since Full-Flow Staged Engine uses preburned fuel/OX-rich gases in combustion chamber, don't those exhaust fumes produced by the preburner somehow unbalance or 'pollute' the pure combustion of fuel ...
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Challenges in Development of small scale liquid propellant engines [closed]

Being aeronautical engineering graduate, I have gone through huge literature regarding design of Liquid propellant engines(LPRs). But as I am planning to develop small LPR based on gasoline and oxygen....
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2answers
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What is producing the orange-brown smoke in the exhaust of some North Korean missiles?

Accompanying a newsreader's report of North Korea's launch of a new long-range (claimed up to 10,000km) missile is footage of a launch in which the rocket produces clouds of orange/brown smoke. ...
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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 ...
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1answer
73 views

The structures in regenerative cooling method and structural strength?

The jacket of tubes used to cool the nozzle and the combustion chamber in rocket engine, does it also give some structural strength? Does it have any function in regards to withstanding the pressure ...
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2answers
178 views

How is gas put back into the tanks once liquid has begun being pumped out?

I am trying to build a rocket with liquid fuel and oxidizer that is being pumped to the injectors/combustion chamber using electric motors/pumps. Assuming that the oxidizer and fuel are liquid, wouldn'...
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1answer
424 views

How does a gas generator engine begin ignition?

I am designing a liquid fueled amateur rocket with my brother, and settled on a gas generator engine. We understand the concept and process, however we are still confused on how the engine is ...
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3answers
331 views

Is there a demand for large liquid engines (> 5 MN)?

In other words, why was the F1 rocket engine programme stopped? Is there a sense that solid motors can take care of high thrust cases in a better way? Or is it an unfortunate fallout of the end of the ...
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2answers
550 views

What are these thirteen purple grape-like things inside this tank?

I am not sure this is a view of the inside of a liquid propellant tank, and even if was, not sure if it belongs to a Falcon 9 per se. But there are places for fourteen round objects at the far end, ...