[ 3 / biz / cgl / ck / diy / fa / ic / jp / lit / sci / vr / vt ] [ index / top / reports ] [ become a patron ] [ status ]
2023-11: Warosu is now out of extended maintenance.

/sci/ - Science & Math

View post   
File: 97 KB, 1024x768, innovative-picture-of-a-space-rocket-pictures-wallpaper.jpg [View same] [iqdb] [saucenao] [google]
9727333 No.9727333 [Reply] [Original]

i come to you with a question I haven't found an answer to through googling.

just now I wondered how rockets propel themselves in space. i know about newton's third law and what it means in that context, but i don't understand the following: wouldn't the vacuum of space "suck out" the pressure of the oxidisation chambers in the thrusters, thereby negate any acceleration? how can anything that has been ignited "fire" when exposed to the vacuum?

i am not very knowledgeable about these things and would be grateful for an answer

>> No.9727364
File: 95 KB, 604x704, double brainlet.png [View same] [iqdb] [saucenao] [google]
9727364

>>9727333
>this thread again

Air isn't required since the two things that push against each other are rocket exhaust and rocket bottom.

>> No.9727385

>>9727364
that wasn't my question at all. i understand how the propulsion works, but seeing as there is an opening in the oxidation chamber, what prevents the vacuum of space from just sucking out the propellant energy? or does it not matter?

>> No.9727394

>>9727385
Solenoid valves.

>> No.9727406

In the divergent part of the nozzle the exhaust gases flow at high suersonic spees, so difference of pressure cannot "climb" inside the nozzle (check supersonic flow behavior), so the outside vaccum wouldn't be able to "suck energy" from the combustion chamber.

>> No.9727422

>>9727406
>>9727394

thanks man

>> No.9727450

>>9727333
>wouldn't the vacuum of space "suck out" the pressure of the oxidisation chambers in the thrusters, thereby negate any acceleration
Vacuum is just (for the purposes of propulsion equations) a lack of pressure. If your expanding gases in the combustion chamber reach, say, 1200 PSI of pressure, the different between 14.7 (earth atmosphere at sea level) and 0 PSI is pretty minor by comparison.
Note that if you took it to the other extreme, and imagine that you had an ambient atmosphere of 1200 PSI and were for whatever reason unable to generate more pressure than that in the combustion chamber, mass wouldn't eject and you would have no thrust, just an open bottle of gas. You NEED that difference in pressure to expel matter.

>> No.9728510

>>9727333
Minor note, vacuum doesn't suck, pressure pushes. There is no pull of vacuum on pressure; there is simply no resistance in vacuum to stop the pushing of pressure. When you put your hand to a nozzle of a vacuum cleaner, it isn't the vacuum that holds your hand to the nozzle but the air pressure in the room you are in that holds your hand to it.

>> No.9728784

The "sucking out" of the exhaust gases is what provides the thrust in the first place, since it is actually the gases pushing themselves out. In a vacuum there is nothing to resist the expansion of exhaust so rockets work even better than they do in air.

>> No.9728866

>>9727333
Don't listen to these brainlets. There's no equal and opposite force being applied to the rocket when a gas comes out of a rocket in a vacuum. The resistance that the gas creates when coming out of a rocket in the medium of air is what creates the lift, not the just the fact the gas is coming out of the rocket because that's retarded.