Questions tagged [engine-design]

Questions regarding the design or design process for a propulsion system.

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Combustion chamber pressure calculation [duplicate]

A liquid propellent rocket engine: how is combustion chamber pressure calculated? Is it the different between turbopump outlet pressure and the drop in the injectors (losses aside)? Thanks!
Mariner's user avatar
  • 11
2 votes
0 answers
65 views

Would (Dual Spool and Concentric Powerhead) FFSC Cycle engine be possible to engineer

I,ve been wondering if it was possible engineer and how we would we work it out DUAL SPOOL FFSCC ENGINE with concentric core and individual concentric turbine inside one another and maybe it could ...
ALPHA X FUTUR COMPANY AEROSPAC's user avatar
3 votes
1 answer
191 views

RS-25 Component weight

I need to determine the weight for specific components of the RS-25 Rocket engine. Namely the combustion chamber and nozzle separate from all other engine components? I must have found hundreds of ...
Slartibartfast's user avatar
3 votes
2 answers
586 views

Fueling the RS-25 Turbo pumps?

Is there any way to know the weight of Fuel / Oxidizer consumed by just the turbo pumps of the RS-25 rocket engine?
Slartibartfast's user avatar
1 vote
1 answer
137 views

Question on improved SSME thrust chamber construction

How do you get the closed out copper liner of the thrust chamber, which is hour glass shaped, into a jacket that is also the exact same shape like shown? I'm gonna guess it was done by diffusion ...
Meatball Princess's user avatar
0 votes
0 answers
94 views

Can coking be avoided by pumping fuel after shutdown?

As I understand it, coking in kerolox engines occurs when the engine shuts down and fuel flow stops, causing fuel still in the coolant channels to overheat and decompose. Can this problem.be avoided ...
Abdullah is not an Amalekite's user avatar
1 vote
0 answers
116 views

Does an overexpanded nozzle behave like a suction cup?

It is generally said that, to obtain optimal specific impulse, a nozzle should be just the right size that the exhaust pressure is equal to the ambient pressure. Quoting this answer, a relevant ...
Charles Staats's user avatar
3 votes
0 answers
144 views

What are the major tradeoffs for a launch vehicle having either one 400 kN engine or eight 50 kN engines?

Given the problem of choosing to build and launch a small rocket to put a smallsat into orbit with either of these two configurations, what are the major tradeoffs between them? For specific issues ...
Muhammad Ahsan's user avatar
2 votes
0 answers
143 views

What was the exhaust pressure of the Saturn V? [duplicate]

I am trying to write some code to simulate rocket launches, and I am doing a proof of concept using the Apollo 11 as a model, to fill my values. When calculating thrust I am using the equation: F=m⋅Ve+...
owinius's user avatar
  • 31
0 votes
0 answers
44 views

How to calculate the tank boost system for the displacement feed system?

There is a liquid rocket engine running on two components: highly concentrated hydrogen peroxide and kerosene, fuel vapor is ...
Андрей Александров's user avatar
2 votes
1 answer
93 views

Combustion stability for the second stage of Sea Dragon

I was listening to a video about SHLV's (Super Heavy Launch Vehicles), and Sea Dragon's first stage engine was mentioned. In terms of combustions stability, the suggested fix would be large combustion ...
AnarchoEngineer's user avatar
1 vote
0 answers
50 views

Rough values for the staytime or characteristic length of the combustion chamber of an oxygen/methanol rocket engine?

I'd like to have some idea of the staytime or characteristic length of the combustion chamber of an oxygen/methanol rocket engine. Are there sources for this, or a way to estimate it? I've tried, but ...
Kevin's user avatar
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2 votes
0 answers
103 views

Contraction Ratio Impact on Performance for Liquid Rocket Engine

How does one go about calculating the necessary contraction ratio (combustion chamber/nozzle throat cross sectional areas) of an engine with these parameters known... thrust nozzle throat area mass ...
Frahanco Deressa's user avatar
1 vote
1 answer
98 views

Multi-stage combustion products?

Okay so I've never seen anything about this before, and that's probably for a very obvious, very simple reason I am far too dim to think of, but here goes: Most combustion reactions in rocket chambers ...
AnarchoEngineer's user avatar
1 vote
0 answers
155 views

How to find the correct size and angle for a conical nozzle on a rocket engine? [closed]

So I need to know the equations for finding the size and angle for a conical nozzle. I am making a rocket engine and I decided the conical nozzle would be the easiest to build. The rocket is going to ...
Anish Kommireddy's user avatar
6 votes
0 answers
235 views

How do spacecraft protect their engines from micrometeroids?

A meteoroid impact on an engine bell can easily rupture a coolant pipe. Or it can create an imperfection in the backing plate from where cracks can form. Or it can destroy an injector. All of these ...
Abdullah is not an Amalekite's user avatar
0 votes
0 answers
106 views

SSME/RS-25:; Why arent high pressure and low pressure pumps coaxial?

The Space Shuttle Main Engine low pressure pumps to prevent cavitation at the main pumps. This pumps were driven by separate turbines fed by high pressure fluid from the main pumps. Why? It just adds ...
Abdullah is not an Amalekite's user avatar
4 votes
1 answer
765 views

SSME/RS-25: why seal between LOX pump and preburner?

Both the the fuel and oxidiser preburners ran fuel rich. In order to prevent the preburner gas from entering the LOX pump and blowing it up, they had this complex double seal with a gas purged void in ...
Abdullah is not an Amalekite's user avatar
3 votes
1 answer
321 views

Why will the Raptor not face the same turnaround issues as Space Shuttle engines?

The RS-25's notoriously slow, expensive turnaround was blamed on its complexity. The Raptor appears about as complex. Both use regenerative cooling. Both use preburners to drive turbopumps. While the ...
Abdullah is not an Amalekite's user avatar
0 votes
1 answer
112 views

How does SpaceX Raptor deliver a more benign turbine environment?

Raptor has been claimed to be able to deliver "long life ... and more benign turbine environments". https://en.wikipedia.org/wiki/SpaceX_Raptor The Raptor has hot oxygen flowing out of the ...
Abdullah is not an Amalekite's user avatar
7 votes
2 answers
684 views

Does methalox fuel have a coking problem at all?

Methane was chosen for SpaceX Raptor because it has less coking problem that kerosene. But does it completely eliminate it? If not, how much less severe is it? I googled 'thermal decomposition of ...
Abdullah is not an Amalekite's user avatar
1 vote
1 answer
235 views

Can a spinning water film cool an engine cheaper and better than ablative?

Ablative cooling us an incredibly simple way to cool a liquid rocket engine, when compared to regenerative cooling. But ablatively cooled engines are (presumably) hard to refurbish. Why not inject a ...
Abdullah is not an Amalekite's user avatar
2 votes
0 answers
106 views

Do smaller engines have a higher thrust to weight ratio?

For a given chamber pressure and shape, thrust is proportional to nozzle area, which is proportional to the square of dimensions mass is proportional to the volume, which is proportional to the cube ...
Abdullah is not an Amalekite's user avatar
4 votes
1 answer
1k views

Why do the Titan SRBs have an angled engine bell?

Looking at pictures of Titan rockets with solid rocket boosters, the bell is at an angle. Why would they do that? https://historicspacecraft.com/Rockets_Titan.html https://en.wikipedia.org/wiki/...
Blue Skin and Glowing Red Eyes's user avatar
3 votes
0 answers
66 views

Recent GPS III Launch Intended or Unplanned Venting?

Between 14:01 and 14:14 in the following video, there is a significant gas vent happening behind the engine bell: Is this working as intended, or does that appear to ...
HumanJHawkins's user avatar
0 votes
0 answers
53 views

What is a bimodal or multimodal space rocket engine? Especially a nuclear-powered one?

I can't seem to find a specific answer anywhere.... I wonder if it means using the radioactive fuel to power the electronic equipment, purely via natural decay, but also using the same fuel to power a ...
Kurt Hikes's user avatar
37 votes
4 answers
8k views

Why did the Soviet Union decide to use 30 small engines instead of a few large ones on the N1?

The N1 was a big disappointment after exploding on every single launch attempt. From what I have read, it seems like most of the attempts went wrong because one of the 30 engines exploded causing a ...
The Rocket fan's user avatar
1 vote
1 answer
216 views

How to find the average ambient pressure during rocket ascent?

I am trying to find the average ambient pressure that my rocket will flight through during its ascent to then determine the most optimum conditions in my combustion chamber and nozzle. I have ...
stanisverylow's user avatar
3 votes
1 answer
143 views

Equations evaluating engine performance

What kind of equation would best evaluate a rocket engine's performance in foreign atmospheres such as Mars? Does it matter that specific impulse does not consider air resistance? Should I focus on ...
boarbytes's user avatar
2 votes
0 answers
90 views

What engine cycle does the RS-88 and its hypergol derivative use?

A comment on this question Orange lines coming from rocket engine nozzle? stated in part The RS-88 is not a full flow engine and there is not a visible bypass exhaust. ... Perhaps they eject the ...
Organic Marble's user avatar
1 vote
0 answers
113 views

What are better ways to deliver heat directly to propellant in a Thermal Rocket design for use in launch than UV such as in the Nuclear Lightbulb?

Most advanced, high-power engine concepts that I came across aren’t suited for atmospheric launch, so I got curious about what kinds of engines could launch a very heavy craft from the surface of a ...
PedrohSpaceWolfy's user avatar
9 votes
1 answer
606 views

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

Looking at the SSME Wikipedia RS-25 Space Shuttle Engines, the data shown that the thrust at sea level ($F_{sl}$) is 1.816*10$^6$ N, while the thrust in vacuum ($F_{vac}$) is 2.278*10$^6$ N. Knowing ...
Julio Gonzalez-Saenz's user avatar
2 votes
1 answer
199 views

Discrepancies in thrust chamber dimensions for RL10

I've recently been developing some automated scripts in Python for the purpose of calculating engine parameters. I've been using the RocketCEA interface library, which links to NASA's Chemical ...
ecfedele's user avatar
  • 527
5 votes
0 answers
155 views

How Spacex's Raptor Rocket Engine starts?

How does the Spacex Raptor rocket engine start? What are the different stages of startup? Is the propellant pressure in the tanks sufficient to drive the turbopumps and ignite the preburners and then ...
Sebastyen Laroche's user avatar
2 votes
0 answers
142 views

Paraffin wax in solid motors

Paraffin wax is often used in (at least hypothetical) hybrid motors, mostly with N2O or HTP. Could it not, however, be used in a conventional configuration? Running at O/F of 12.4, 60 bar chamber ...
R. Hall's user avatar
  • 812
2 votes
1 answer
644 views

Question Deriving Mass Flow Rates for an Engine

I am trying to follow the calculations made in this blog post for a $50$ lbf. IPA/Nitrous Oxide engine, but cannot seem to get the values the author made for their propellant flow rates. Since the ...
Frank W's user avatar
  • 227
2 votes
1 answer
218 views

Estimations for Gas-Side Wall Temperature Within Rocket Engines

I'm in the process of reading Modern Engineering for Design of Liquid Propellant Rocket Engines and am stuck on this one example given in chapter 4 on the ...
Frank W's user avatar
  • 227
7 votes
1 answer
1k views

Is there an ultimate break-even point with rocket nozzle length or expansion ratio in a vacuum?

I know that in an atmosphere, you don't want your expansion ratio to be too high, or it will cause some big problems, and that vacuum engines are restricted by the space they have to fit in, but if we ...
zucculent's user avatar
  • 248
2 votes
1 answer
215 views

How to calculate catalyst bed geometry (length/radius) for a monopropellant thruster?

Catalyst design is central to the development of monopropellant thrusters and hence, ignoring its importance, as I have realised, is not very good practice. My question is if the mass flow rate, bed ...
R. Hall's user avatar
  • 812
4 votes
1 answer
594 views

Inconsistencies in calculating exhaust velocity

I'm quite sure this is either a small or just plain stupid mistake but my anxiety is getting the better of me. when calculating exhaust velocity this is the equation used: however I keep getting ...
R. Hall's user avatar
  • 812
5 votes
1 answer
207 views

Is there a significant reason why pintle injectors are only used in single configuration?

All of the resources I've managed to track down thus far about pintle injectors concern engines which only use a single, large central pintle for the entirety (or vast majority) of propellant supply ...
ecfedele's user avatar
  • 527
8 votes
1 answer
2k views

What is the purpose of the shrouds surrounding these rocket engines?

While researching the purpose of some rocket engine components, I came across several images of perforated shrouds surrounding the combustion chambers of rocket engines. I was highly curious about ...
Angel Sachse's user avatar
4 votes
1 answer
225 views

Do monopropellants have a characteristic length?

I was reading about calculating thrust chamber geometry, and a key tool seems to be the characteristic length, L*. The engine I'm modelling (hypothetically! please don't take down the question) uses ...
R. Hall's user avatar
  • 812
8 votes
0 answers
442 views

What are the negatives associated with Thrust-augmented Nozzles aka Afterburning Rocket Engines?

An interesting comment here introduced me to the concept of Thrust-augmented Nozzles aka Afterburning Rocket Engines. The pubs I've read on it so far introduce the concept as a way to provide good ...
Organic Marble's user avatar
3 votes
1 answer
139 views

Insights about launch vehicle engine configuration

When dealing with launch vehicles (specifically heavy lifters), there have been a number of different mindsets in terms of engines. The Saturn V used some absolutely massive engines, which was great ...
frank's user avatar
  • 131
6 votes
1 answer
412 views

Reference request: Rocketdyne Document R-3896-4 "F-1 Rocket Engine Illustrated Parts Breakdown"

Various sections of the Rocketdyne F-1 document R-3896 can be found scattered about the web, but I can't find R-3896-4. It's described as R-3896-4 F-1 Rocket Engine Illustrated Parts Breakdown This ...
Organic Marble's user avatar
4 votes
1 answer
217 views

Discrepancy in local Mach behavior between CEA and other sources

I'm exploring some designs using the NASA CEA (Chemical Equilibrium with Applications) code and I ran into a discrepancy between CEA predicted values for local Mach number at the exit plane and values ...
ecfedele's user avatar
  • 527
1 vote
1 answer
54 views

Would pressure oscillations at the inlet of a liquid engine turbo-pump subside at the outlet, or would they get amplified?

Would pressure oscillations at the inlet of a liquid engine turbo-pump subside at the outlet, or would they get amplified? What are the factors that decides the change in the amplitude of pressure ...
Jithin's user avatar
  • 61
4 votes
1 answer
659 views

How is a desired chamber pressure achieved in a liquid rocket engine

Before everyone responds that this has been asked before, I have read through every relevant post I could find here and believe my question has not been clearly covered. I also understand that "...
rockets_go_boom's user avatar
3 votes
1 answer
281 views

Where do the numbers 101,972 and 3,600 come from in terms of Thrust-Specific Fuel Consumption (TSFC or SFC)?

Online, on sites such as Wikipedia's for Specific Impulse and Thrust-specific fuel consumption, there are these units: 101,972/x g/(kN·s) and 3,600/x lb/(lbf·hr) Perhaps 3600 comes from the number of ...
Kurt Hikes's user avatar

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