# Questions tagged [rockets]

Questions regarding the boosters or thrusters used to propel man-made objects. For rockets firing opposite the primaries, see [retrorockets]. See wiki for other related tags.

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### What permission do I need to build a rocket that goes to space? [closed]

I wanted to build a rocket that goes to the karman line at 340000 feet which is technically space. I know the rules and what I need to get to launch the rocket such as faa clearance and more but I ...
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### Rocket propellant control

In a liquid propellant rocket, how is the quantity of propellant controlled? - for two purposes. One for achieving the required "ratio" of propellants, and 2nd, to control the thrust of the ...
25 views

### How could I find the pressure and/or the Isp at the exit of a rocket nozzle if I have data for the throat and comb. chamber?

I've been looking at this for some time and working with CEA which will only give me data points for the pressure, temperature, Isp, etc. for the Injection, Combustion Chamber End, and the Throat; but ...
21 views

### What would it take in terms of energy to lift a space X re-useable rocket to LEO, then take 10 kg of cargo to GEO Trans and GEO orbit?

I want to calculate the total energy from the fuel production all the way to the GEO orbit it takes to deliver 10 kg of payload? The idea is to obtain a total cradle to grave figure. It does not have ...
1k views

### How does a command sent to a rocket or rover look like?

I think the answer is quite clear. Let's say when Mission Control decides to let Perseverence move forward for 3 seconds with a speed of 10 (whatever..) What syntax would this command have? Im ...
164 views

### What does 'a nudge' mean in the context of rocketry?

The following paragraph is from a wired.com article: When I visited this past fall, SpinLaunch employees were still unpacking from the move. As we walked among giant sheets of steel, Yaney explained ...
3k views

### Why are Starship landings so difficult when SpaceX has landed so many boosters?

Per Wikipedia, SpaceX has landed boosters successfully 79 out of 90 times. Yet Starships seem to be reliably exploding upon landing. What is so different about the two that Starships are so much more ...
206 views

### Why is hydrogen better than helium as remass?

I just watched a very good YouTube video on why nuclear engines might be useful, and it also goes into why Hall Effect thrusters are super good at squeezing obscene ISP out of things. During the video,...
145 views

### Why are propellant tanks filled from the bottom?

It seems that the norm is to (fast-) fill fuel and oxidiser tanks from the bottom. For example, on this drawing of the Saturn S-IC stage you can see the LOX and RP-1 fill valves at the bottom of the ...
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### Clustering of liquid fueled rocket engines

Which rocket first used clustering of liquid fueled rocket engines on their first stage?
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### Apogee estimate starting from simplified one-dimensional numerical simulations

I asked a question on pen and paper apogee estimation and got an answer from @tom-spilker that called my attention: He said that he quickly estimated an inclined launch apogee from the results of a 1-...
96 views

### Why the max dynamic pressure might not happen at maximum drag instant?

I understand that is that when a rocket accelerates the drag force grows dramatically since the force is related to velocity squared. But, at the same time, the density is decreasing, so the force is ...
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### Pen and paper apogee estimation

I have calculated the apogee of a 2.5kN avg. thrust sounding rocket once ignoring drag and then assuming maximum constant (magnitude and direction) drag after burnout. Here are the figures I used in ...
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### Pressurant gas line design considerations

I am trying to understand the constraints on pressurant gas line sizes and lengths. For a static volume, the lines can be small in diameter because there is no significant flow velocity and therefore ...
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### Why does the RD-0110 Injector have a larger cone spray angle in the outer element rather than the inner element?

Wouldn't a large cone spray angle in the inner element (oxidizer) impinge with the outer element spray cone (fuel) and facilitate better atomization and mixing? Here are the RD-0110 Injector specs:
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### Rocket engine test bed structure

Rocket engine thrust will eventually "lift" a certain amount of weight, to a certain height. For Saturn V, they used 5# F1 engines, each of which produced a thrust sufficient to lift ...
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### Pendulum rocket fallacy - so why *do* skyrockets have sticks?

This question is inspired by two, linked questions. Skyrockets (of the pyrotechnic/firework kind) have guide sticks, which are (according to internet sources) to enhance stability: "The guide ...
5k views

### What is the “pendulum rocket fallacy” as it relates to analogizing a pencil balanced on a finger to maintaining attitude of a hovering rocket?

I've received comments that explain to me that the analogy between rocket attitude control during a hovering maneuver and the act of balancing pencil on the end of a finger is a helpful and good one; ...
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### Is streamline body shape essential for propagation in the vacuum of space?

Streamline body shape is essential for reducing friction during motion in fluids like liquid and gas, including our dense atmosphere. Is streamline body shape also essential for propagation in the ...
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### Why does SpaceX use Methane instead of Butane? [duplicate]

Genuinely, curious on why they use Methane as it's much harder to compress and liquefy whereas butane liquefies easily and is highly compressible.
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### Flying saucer shape rocket vs cylindrical shape rocket

Here's my hypothesis- Cylinder shaped large rocket is not suitable for vertical landing due to its high center of mass and bulky weight. However an equally weighing saucer shape rocket has more ...
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### Is it possible to launch a rocket with steam by using a fission reactor?

The idea is to use a fission reactor to turn water into steam pumping it outside the reaction chamber through heat pipes.
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### Static Fire Tests: How is the rocket prevented from flying?

In rockets like Starship, if 35 Raptors are firing at same time, then in a full-duration static fire test there would be enormous loads being exerted from 35 raptors, on the clamps holding the rocket. ...
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### Injector design

I want to design a coaxial swirl injector for a bipropellant liquid rocket engine. I've tried to search a lot but can't find many references for the same. Has anyone worked on a coaxial swirl injector ...
3k views

### What is this line, what is it called, what is the reason behind it?

I started following SpaceX recently. I used to read the updates but now I am diving deeper to learn new things. SpaceX is fascinating and I really like everything about it. But I have question, I don'...
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### Can someone explain the SN10 landing failure in layperson's terms?

The things I can't understand from what Elon tweeted are: "engine was low on thrust due (probably) to partial helium ingestion" There are only tanks for liquid oxygen and CH4 - where did ...
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### What will be the final Starship prototype?

So far, Spacex has made and destroyed/launched Starhopper,MK1-MK4, and SN1-SN10. They also have SN11 on the launchpad and BN1,BN2, and SN15-SN20 under construction. What will be the final Starship ...
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### Will i be able to see the SpaceX tonight launch from Ocala, Fl?

Im currently in Ocala, FL and SpaceX launches a rocket tonight (March 9th) from Cape Canaveral. Will I be able to see it given the proper conditions?
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### Why did the SpaceX Starship SN10 explode?

Much to everyone's relief. The SpaceX Starship SN10 successfully completed its flight and landed..... But, sometime later, It exploded! Why? And did it have anything to do with the fire near the ...
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### Earth Launch System with Water Propellant

Water based thrusters have been proposed (and possibly tested by now) for use in satellites and other in-space vehicles - see this NASA article. The idea is to perform electrolysis on the water to ...
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### Use of SRB for Saturn V [duplicate]

In 1967, a solid fuel rocket motor with 260 inch diameter and 89 inch throat dia, was tested, and it was found to generate 5.8 million pounds of thrust. This was much higher than the F1 engines used ...
147 views

### Why don't silo-launched Minuteman missiles incinerate themselves at launch?

Whilst cobbling together an answer for this question, I found myself thinking about the effects of hot rocket exhaust on a rocket launching from a confined space. I assumed it would be generally ...
207 views

### What happened to tripropellant rockets?

IIRC, tripropellant rockets can deliver superior performance compared to bipropellant rockets (at the cost of added complexity). Now, I know that there is the Li/H/F combo, but it isn't used because ...
406 views

### Solid state thrust vectoring

Usually thrust vectoring for the whole rocket is done by changing the orientation of individual engine(s) by hydraulic/electric actuators. So in this system the engine simply moves and with it the ...
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### How do I calculate thermochemical properties of mixed gases?

I'm working on a rocket project, and my design of engines is stalled. I need to be able to calculate the Cp, Cv, and R for mixtures of O2/CH4 (stoichiometric or fuel-rich mix) and CO2/H2O (result of ...
108 views

### How to select appropriate orbital rocket stage thrust?

I’ve been working on a preliminary design of a small-lift launch vehicle capable of sending a small satellite into LEO. Given the required $\Delta v$ (~9 km/s for LEO), the mass distribution, ...
146 views

### If a company/agency has already developed a kerolox/hydrolox rocket, is it wise for them to switch to an all-methalox rocket? (to lower costs)

Multiple rockets, such as the Atlas V or Saturn V, have used the combination of a kerosene/liquid oxygen (kerolox) lower stage for higher density and thrust within the atmosphere and a liquid hydrogen/...
96 views

### What happens to the debris of a rocket that exploded or crashed? Is there a dedicated effort to cleaning the debris?

Assuming that everything is not vaporized, one would think that all waste is collected and incinerated. Does SpaceX, NASA, etc have a dedicated team/effort to cleaning up this debris?
141 views

### Most open source spaceflight missions revealed unintentionally

As of 2021 there are few fully open source satellites (OSSI-1, UPSat, FossaSat-1, Oresat, some more?) and numerous student groups building and documenting rockets. These projects are intended to be ...
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### Rocket engine with lowest Isp to reach orbit

Which engine with the lowest possible specific impulse has reached orbit propelling a given rocket? There is a page at Wikipedia that compares orbital engines but some engines are missing Isp value ...
162 views

### What if we launched rockets from space using the slingshot method and centripetal force? Would that be possible?

Would we have to build a orbiting launch station that uses centripetal force to launch the rockets? Or a station that freely floats through space not in a planets orbit? Would something like this ...
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### What is the inlet and outlet pressure of Merlin LOX/RP-1 turbopump?

I got the inlet and outlet pressure of Saturn V engines turbopumps here, but I couldn't find the turbopump pressure of the Merlin engine of Falcon 9.
3k views

### Are there any hand-sized rocket engines?

Are there any rocket engines that are small and light enough to be held in one or both hands? Gas, liquid and hybrid designs are fine but solid motors are excluded (with the exception of solids that ...
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### How big is an orbit of “X by Y miles”?

While reading the NASA overview of Apollo 11, says: Apollo 11 launched from Cape Kennedy on July 16, 1969, carrying Commander Neil Armstrong, Command Module Pilot Michael Collins and Lunar Module ...
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### Rocket fuel cost to launch 1 kg to orbit

I have 2 questions about the cost of liquid rocket fuel to launch (anything) to LEO orbit. Let's assume we use fuels used in commercial spaceflight today (probably LOX+LH2 or LOX+RP-1 etc.). What is ...
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### What are the implications of North Korean black and white patterns on missiles?

Black and white patterns on rockets were originally intended as roll patterns. They helped as a visual back-up for acceleration sensors measuring the roll, as discussed in this previous question What ...
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### Calculating Pressure Inside Combustion Chamber

I am trying to calculate the pressure inside a combustion chamber of a rocket candy. My "engine" is made out of PVC with an internal diameter of 1/2 in. Are there ways for me to calculate ...
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### Pressure levels inside rocket liquid oxygen tanks?

What is the pressure levels inside rocket liquid oxygen tanks, at launch time? The question is for the minimum and maximum (known) levels of pressure inside such tanks. I am asking for any rocket ...