Skip to main content
50 votes
Accepted

Why do rocket nozzles flare?

The purpose of this nozzle is to achieve maximum acceleration of the flow to obtain the highest possible exit velocity. The shape of convergent / divergent (de Laval) nozzles is dictated by the ...
Organic Marble's user avatar
48 votes

Could a deadly fire start within a spacesuit?

Yes, because a deadly fire has started within a spacesuit. Fortunately no one was inhabiting it at the time (although a nearby person was injured) In 1980 a Shuttle EMU being tested erupted in flames ...
Organic Marble's user avatar
33 votes
Accepted

Are there any known atmospheres that would support traditional combustion engines?

The short answer is no -- an internal combustion engine needs to pull oxygen from the air to operate, and no solid bodies in the solar system have that kind of atmosphere. (You could, of course, carry ...
Russell Borogove's user avatar
25 votes

Why do rocket nozzles flare?

The gas at the narrowest part (the throat) of a convergent-divergent nozzle used in a rocket engine is ideally moving at the Mach 1, the speed of sound. This creates a choked flow condition. After the ...
David Hammen's user avatar
20 votes
Accepted

Platinum Colloid in Liquid Hydrogen fuel to increase fuel efficiency

Short answer: no, it won't increase the performance of the rocket. Platinum (or other catalysts) can be used in fuel cells, where the purpose is to get a chemical reaction at (relatively) lower ...
Andy's user avatar
  • 5,178
19 votes
Accepted

How exactly is the pressure inside the combustion chamber monitored?

The pressure sensors do need to be shielded somehow from the full fury of the combustion chamber. Here's a schematic showing the connection of the Space Shuttle Main Engine chamber pressure (Pc) ...
Organic Marble's user avatar
17 votes
Accepted

How do you confirm ignition in the combustion chamber of a rocket?

For the Space Shuttle Main Engine, four checks were done to set the "Ignition Confirmed" condition. The High Pressure Fuel Turbopump shaft speed was checked against a minimum limit. The Main ...
Organic Marble's user avatar
13 votes
Accepted

What are the advantages of Ox-rich staged combustion?

According to the super-detailed and very informative NASA-CR 165404 Fuel/Oxidizer-Rich High-Pressure Preburners, the primary advantages of hydrocarbon-fueled oxidizer-rich staged-combustion engines is ...
Organic Marble's user avatar
11 votes

Do any rocket engines besides the F1 need/require baffles?

In early versions of the Space Shuttle Main Engine (SSME), the main injector was baffled. The baffles were formed by extra-long liquid oxygen posts protruding from the injector face. Block IA ...
Organic Marble's user avatar
10 votes
Accepted

Can I make my own RP1?

I'm going to start off with a warning: if you want to get started with model rocketry, it is about a thousand times safer and easier to start with off-the-shelf solid rockets. Don't even consider ...
Russell Borogove's user avatar
10 votes

Detonation Liquid rocket engine

There are three types of aerospace detonation engines I heard of, one of which being an air-breather. The first one is a variant of the Shock-Induced Combustion Ramjet, or Shcramjet (and yes, I also ...
Eth's user avatar
  • 779
10 votes
Accepted

Does peroxide spontaneously decompose when introduced into hot combustion chambers?

HTP will sustain a combustion reaction without a catalyst once ignited, but it's not clear to me if the reaction proceeds quickly and smoothly enough to be a good idea for rocket combustion chambers. ...
Russell Borogove's user avatar
9 votes

Are there any known atmospheres that would support traditional combustion engines?

It seems unlikely in principle Standard combustion engines rely on burning fuel in an oxidiser taken from the atmosphere. On earth we have an atmosphere which is about one fifth oxygen which does a ...
matt_black's user avatar
9 votes

How much of the exhaust speed is due to combustion and how much is due to the injection?

$v_{\rm injection}$ of liquids, as a rule of thumb, doesn't get higher than 10 m/s (dictated by a general limitation of pressure losses). Given that exhaust velocity could be 2500 - 4500 m/s, you can ...
Arris's user avatar
  • 331
8 votes

Why do rocket nozzles flare?

The combustion of propellants is an exothermic process, it mainly provides heat. Initial velocity (think of the turbo pumps) and the changed specific gas constant of the combustion product are ...
Andreas's user avatar
  • 1,385
8 votes

What happens when LOX and H2 are injected into the combustion chamber of a rocket?

Mixing oxygen and hydrogen at ambient temperature doesn't do anything exciting -- it just yields a mix of the two gases. In the presence of sufficient heat, mixed oxygen and hydrogen will burn, ...
Russell Borogove's user avatar
8 votes
Accepted

Is there a distinct flame-front in a liquid-fuelled rocket combustion chamber?

Partial answer because based on a simulation doesn't address the secondary question about changes with throttling The paper CFD SIMULATION OF A LIQUID ROCKET PROPELLANT (LH2 /LOx) COMBUSTION CHAMBER ...
Organic Marble's user avatar
7 votes

How are rocket propellants ignited repeatedly without the ignition source melting

Restartable hydrogen-oxygen engines like the RL10 (used on the Delta and Atlas upper stages) and J-2 (used on Saturn) use spark ignition. On the J-2, the spark igniter is positioned above the fuel ...
Russell Borogove's user avatar
6 votes
Accepted

Cooling a hydrolox rocket with Water

It would work, but it would be far from optimal. Heat recovered from the nozzle would result in steam much colder than combustion chamber temperature (after all, we never allow the nozzle to reach ...
SF.'s user avatar
  • 55k
6 votes

Why do rocket nozzles flare?

You're missing one thing: the combustion chamber (hidden behind the piping at the top of the photo). Here's a cross-section of a rocket engine: Thrust is defined as: F = qVe +(Pe-Pa)Ae F = ...
Hobbes's user avatar
  • 128k
6 votes

How exactly is the pressure inside the combustion chamber monitored?

I assume you talk about average static pressure, not total pressure or high frequency acoustics. If this is untrue then please clarify the question. A boundary layer gets it's pressure from the main ...
Rikki-Tikki-Tavi's user avatar
6 votes

How do you confirm ignition in the combustion chamber of a rocket?

How do you confirm ignition in the combustion chamber of a rocket? Sometimes, you don't. Pressure sensors, flow sensors, and such are yet another device that can fail. Moreover, what if nothing can ...
David Hammen's user avatar
6 votes
Accepted

Conditions on Titan under which human breath can be set to fire

Wikipedia says of the composition of the lower atmosphere: Because methane condenses out of Titan's atmosphere at high altitudes, its abundance increases as one descends below the tropopause at an ...
Steve Linton's user avatar
  • 19.6k
6 votes
Accepted

How is pressure distributed in the combustion chamber of a rocket engine?

This paper CFD SIMULATION OF A LIQUID ROCKET PROPELLANT (LH2 /LOx) COMBUSTION CHAMBER claims that the chamber properties are essentially constant until the constriction starts towards the throat.
Organic Marble's user avatar
6 votes

Other than rockets, have internal combustion engines run in space?

With the clarification, then yes, "internal combustion engines" (ICE) as defined in the question have flown in space over 100 times. Each space shuttle orbiter had three of these ICE ...
Organic Marble's user avatar
6 votes
Accepted

How does a liquid rocket engine prevent the combustion from going back in?

In bi-propellant engines, normally by making sure that full mixing only occurs inside the chamber, using separate injectors for fuel and oxidizer. If doing early combustion to power turbines you only ...
GremlinWranger's user avatar
5 votes

Are there any known atmospheres that would support traditional combustion engines?

In our solar system? No. None of the other planets would support a standard ICE from earth. In other systems? We think we've found some other earth like planets which are in the habitable zone which ...
Evan Steinbrenner's user avatar
5 votes
Accepted

How are the combustion chamber length and diameter decided

You can referthis book Modern Engineering for Design of Liquid-Propellant Rocket Engines chapter 4. It depends the on the number of performance parameters such as $C_f, C^*$ and $I_{sp}$. From which ...
Vasanth C's user avatar
  • 1,161
5 votes
Accepted

What would happen if we ignited one of the gas giants?

Combustion requires a fuel (hydrogen), an ignition source (your enormous explosive), and an oxidizer. There's a very small amount of oxygen in the atmospheres of the gas giants, almost all of it ...
Russell Borogove's user avatar
5 votes
Accepted

I don't know where to start with the calculations - rocket engine

The reason you can't finish your calculations is that you are missing half of the engine. You are going to have to make some decisions about the nozzle in order to get exhaust velocity. I'll make some ...
Organic Marble's user avatar

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