Questions tagged [propulsion]

Systems for propelling a spacecraft from one place to another, such as rockets.

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Is thermal soakback from the engine a problem for rocket stages? Especially ones that complete several burns over several hours (e.g. S-IVB, Centaur)?

Thermal soakback is a phenomenon whereby a hot, operating engine transfers heat into the spacecraft, usually conduction through the engine mounts. I've only ever seen this problem discussed with RCS ...
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1k views

Potential improvement to BFR or New Glenn if equipped with aerospike exhaust on their engines?

Aerospikes basically tackle the issue of the variability in required expansion ratio for a rocket engine to be efficient at a given altitude. A recent example though mired in legal issues is a small ...
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155 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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479 views

What upgrades does the Merlin 1D need to increase its time between overhauls to 1000 hours?

This is a question I've been pondering for the last few weeks after I back-calculated the details of the Merlin 1D engine. Just as a thought exercise, I wanted to see what upgrades the Merlin 1D would ...
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126 views

Relationship between part dimensions and performance of ion electrospray thruster

I got the relationship between power, thrust and specific impulse for an ion electrospray thruster as follows: $$P/T= 1/2 \times g_o \times I_{\mathrm{sp}}$$ Where: $P$ = power required (in Watts), $...
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161 views

Purging process of a rocket engine

Does spacex purge Falcon 9 engines after landing ? If so, which gas is used for purging?
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153 views

What is the droplet size that is desirable for pintle injectors?

The pintle injectors tend to generate droplets after impingement of the fuel and the oxidiser stream and I understand that the droplets will be premixed. In such a case, even a larger premixed ...
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625 views

Pulse Rocket Engine

How feasible would a rocket engine that ignited fuel in fast, high pressure pulses be. This type of engine would be especially applicable for low thrust burns such as for the raising of a small ...
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80 views

Maximum speed of rocket propellant flow?

In reading this question (Limiting factors of liquid rocket engine thrust), it prompts me to ask if there is an upper limit in how fast the propellant/oxidizer can be pumped into a combustion chamber ...
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118 views

Could a laser ablation-based propulsion system really accelerate an object to 0.001 c?

Comments below this answer suggests that a laser ablation-based propulsion system, where the laser is separate from the object to be accelerated, could accelerate an object to about 1/1000 of the ...
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109 views

Electromagnetic engines in heavy radiation regions

What sorts of peculiarities might affect an electromagnetic rocket (VASIMR or Magneto-Inertial Fusion) crossing Jupiter's radiation belts? Could all of that energy fry a magnetic thrust chamber and ...
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98 views

Electron buildup in Hall effect thrusters?

I was thinking about the Hall Effect Thrusters and how they are able to produce thrust. There's something that I don't understand: when the hollow cathodes emit electrons to neutralize the flow at the ...
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47 views

Where are Falcon 9 1st stage GN2 tanks located?

Is nitrogen propellant for the two cold gas thrusters pods contained in the interstage? The view we have from the B5-B1050 recovery shows several small COPV(s) pic1 Here you can see where the cold gas ...
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50 views

Why might krypton have a lower utilization fraction than xenon for ion propulsion, and what can be done to improve it?

A comment below Why will Starlink satellites use krypton instead of xenon for electric propulsion? links to the 2011 preprint A Performance Comparison of Xenon and KryptonPropellant on an SPT-100 Hall ...
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47 views

Are there substances that can effectively mined from asteroids that can be used for ion thrusters?

The most popular ion thruster design seems to use Xenon. Unfortunately, due to it's low boiling point Xenon isn't easily available in space. Are there other materials from which ion thrusters could ...
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81 views

How do you calculate burns needed to land?

Assume I was landing a rocket and wanted to do calculations on how to correctly land. How do you determine at what time you fire the engine and at what power to successfully land on a predetermined ...
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85 views

How is supersonic rocket exhaust able to match sea-level pressures?

I understand that the diverging portion of a rocket nozzle speeds up the flow and also expands it, in order to best match ambient pressure outside. However, doesn't higher speed flow lower the ...
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175 views

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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67 views

Mars Sample Return Earth Return Orbiter — which propulsion system for what?

Many sources (eg this one) show the Mars Sample Return Earth Return Orbiter with both ion and chemical propulsion, and also state that it will be launched on an Ariane 6, but I can't find a clear ...
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36 views

Anyone know of a “N71” Hall Effect Thruster currently in production or development?

In a NASA Goddard Q&A transcript for an upcoming proposal, the NASA representative mentioned that the mission designers were considering the "N71" Hall Effect Thruster as an option for an upcoming ...
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48 views

Are there any staged combustion cycle rocket engines under 1000 kN? Is it easier to produce larger engines with this type of engine cycle?

I found that most engines developed with staged combustion cycles are inherently quite powerful. Are there any engines which was developed with the staged combustion cycle with a thrust under 1 MN. ...
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91 views

Could a Soyuz-MS deorbit after a failure of its deorbit engine?

The scenario: A Soyuz-MS spacecraft is on-orbit and ready for its deorbit burn. The crew then discover that there is a fault in the propulsion system and the deorbit engine can't fire. The craft is ...
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41 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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61 views

How to make a orbital launch tube work?

Normal rockets would not work in a pressurized tube, but could a stage be made for the diagonal launch tube to save fuel and weight? Can the bottom stage be nuclear powered? Unlike the piston launch ...
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73 views

Is it feasible to take liquid Helium in a Pressure Fed System?

Can liquid Helium be flowed through a heat exhanger to increase its temperature and pressure which will further pressurize fuel-oxidizer tanks.
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98 views

Is there a use case describing the need to perform xenon propellant offloading?

I can understand hydrazine offloading and the hazards associated, but I'm wondering if there is such a need for xenon offloading.
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102 views

Optimal Thruster Layout For Cubesat

I am working on a simulation of a Cubesat for rendezvous. Using the Clohessy-Wiltshire equations I calculate delta-v. Now that I know the thrust needed for operation, I would like to know how to ...
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144 views

thrusters, force torque, distribution matrix , orbit maneuver

I have a few questions about computing torques and forces. I use the same configuration as in the thesis titled An Attitude Control Sysytem Design Based on the Turksat-1b Geostationary Satellite. ...
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48 views

Attitude and orbit thrusters catalog

Typically, when trying to adjust simulation parameters (of orbit control, attitude control...) to real world values in order to validate algorithms with comparisons with past and current mission ...
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70 views

Switching off the magnetic coils in a Hall Effect Thruster

Talking about Hall Effect Thrusters (HET), we can say that the presence of a hollow cathode is relevant to reach a good operation of the thruster. We also can plot the potential-x (trajectory of ...
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70 views

Preliminary design of Propellant ducts

I'm trying to roughly estimate dimensions and masses of propellant and pressurant ducts for conventional upper- & transfer stages. My basic approach follows Barlow's formula for cylindrical ...
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265 views

What are non-rocket-based reaction mass drives called?

There's plenty of talk out there about a certain type of propulsion system, but I don't know the proper name for it. You gather up / buy / otherwise acquire some kind of non-rocket material, like ...
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66 views

How to send a 6-km mirror close to the Sun to propel a light sail?

I have written a paper about a crewed interstellar spacecraft that I propose. I suggest to use either a laser, a Fresnel lens or a mirror to propel the sail of the spacecraft with sunlight. I have ...
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53 views

Freezing problem of hydrocarbon fuels in a LOX cooled engine

I assume that in a LOX/RP-1 engine where RP-1 is used as a coolant, we need not consider the freezing issues. The reason for my assumption is that we need not bring the chamber and injectors to the ...
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26 views

Injectors Diameter and Numbers

how would you determine the diameter and the number of injectors if unlike doublets elements are used? The Data given is: Isp =286 s Chamber pressure= 25 bars Propellant pair: Fuel= Hydrazine and ...
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30 views

Do colloid thrusters generate thrust by using only droplets or pure ions as well? If they only use droplets, how are they the same as electrospray?

In all of the research literature I have read so far, I've seen colloid thrusters explained as devices that gain thrust by releasing only charged droplets from ionic liquids as the exhaust mass. ...
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50 views

How does a “hybrid orbital raising system” based on R-4D (N2O4/MMH) + SPT-100 (Hall effect) work exactly? (Intelsat 38 & 39)

Astronatix's Intelsat 39 lists the two engines SPT-100 Stechkin 1.35 kW Hall thruster. R-4D Marquardt N2O4/MMH rocket engine. 490 N. Question: Why is this combination on Intelsat 39 called "hybrid" ...
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53 views

How to calculate the force drop due to multiple thrusters firing?

When multiple thrusters are connected to one pressurized propellant tank and multiple thrusters are fired simultaneously, this will cause a pressure drop in the supplying pipes and as such a drop in ...
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135 views

Very Low Gravity Bicycle

There are a couple of existing questions about riding bicycles off of Earth. Designing a bicycle for Mars? Can you ride a bicycle on Deimos? Bicycles are lightweight and proved a reliable method ...
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35 views

Converting Discharge Voltage to Temperature? Hall Effect Thruster Calculation

Trying to follow a Hall Effect Thruster design process given in this video: Hall Effect Thruster Design Video In 25:59, there's a calculation in which the presenter takes discharge voltage and ...
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0answers
79 views

Externaly delivered non-nuclear pulse propulsion?

This question asks about the feasibility of an Orion-like pulse propulsion system using chemical explosives instead of nuclear explosives as pulse unit. Unfortunately, those simply lack the energy ...
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0answers
78 views

Transportation on the Mars I Air

Due to the thin atmosphere generating lift on Mars is difficult at a lower speed, Flying is hard until aircraft go supersonic and then it becomes difficult to control(Ref.). The landing would not be ...
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107 views

Simulation of Rocket chambers like in Hall Effect Thrusters

I started learning Solidworks in hopes of being able to run simulation to study rocket chambers. Currently, I am studying the flow of plasma and its interaction with the magnetic field, but ...
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54 views

Generating an electric field for a colloid thruster

I was wondering how the electric field in an electrospray thruster works to ionize particles and propel a micro spacecraft. I was thinking of possible circuits but I wasn't sure what it could look ...
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179 views

Charge to Mass ratio of Ion thruster

For an Ion thruster which emits single charged ions, the charge to mass ratio is find out by considering the charge( whether it is positive or negative) and the mass of that ion.when the ion thruster ...
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29 views

Ion Lifter Thrust Calculation Problem

I've recently started building an ion lifter. I tried calculating the thrust the lifter produces but I came to a value that is way to high for such a small lifter. I'm using a 40kV at 1800mA AC ...
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1answer
114 views

For a DAWN-like solar-electric deep space mission, would using propellant particles much heavier than xenon atoms be beneficial?

For deep space missions using ion propulsion that are power-limited, this answer explains that a large mass/charge ratio ($m/q$) species is desirable. The solar-electric propulsion system used by the ...
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51 views

Help on Rocket Injector Equation

Hello can someone explain me how can I get the value of (6340) because when I try to solve the given values on the book I get (6423.980075) when I round it off it is still not the right answer can ...
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142 views

Can an ion drive attached to an asteroid move it into another orbit if given enough power?

After watching one of the videos from Curious Droid on Youtube talking about asteroid deflection and strikes I had an idea. Ion thrusters provide bits of mass velocities at the needed Isp (5-6 km/s ...
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1answer
68 views

'Space Transit Habitat' source(s) of energy

What are the sources of energy for a Space Transit Habitat(manned) in terms of both propulsion( after passing over the Low Earth Orbit) and required electric facilities)through a 6-8 month voyage to ...