Anonymous at Wed, 12 Feb 2025 08:08:21 UTC No. 16583454

A rocket burns it is fuel???

🗑️ Anonymous at Wed, 12 Feb 2025 08:11:45 UTC No. 16583455

>>16583448
>instantly
Wouldn't that technically be a bomb?

Anonymous at Wed, 12 Feb 2025 08:20:20 UTC No. 16583458

We still don't know how rockets work so this problem is unsolved

Anonymous at Wed, 12 Feb 2025 08:32:28 UTC No. 16583462

>>16583448
>it's fuel
ESL filter, back to your classes.

Anonymous at Wed, 12 Feb 2025 14:41:32 UTC No. 16583677

>>16583448
The answer obviously depends on the orientation of the rockets trajectory in relation to the gravitational gradient

Anonymous at Wed, 12 Feb 2025 15:29:59 UTC No. 16583695

>>16583448
The bomb, because smaller parts of the astronauts will reach a higher altitude after the explosion

Anonymous at Wed, 12 Feb 2025 15:34:46 UTC No. 16583697

>>16583448
if drag is a thing, then 2, if drag isn't a thing, then both equal

Anonymous at Wed, 12 Feb 2025 17:40:10 UTC No. 16583820

I think scenario one is more efficient because of this thought experiment, imagine that the thrust was so low that it burned 99% of its fuel just hovering up out of the gravity well incredibly slowly
and then it only has 1% fuel left

Anonymous at Wed, 12 Feb 2025 19:35:13 UTC No. 16583900

>>16583448
gravity is weaker at higher altitudes so the gradually burning rocket goes higher

Anonymous at Wed, 12 Feb 2025 19:37:04 UTC No. 16583902

>>16583900
lol you have no idea what you're talking about

Anonymous at Wed, 12 Feb 2025 19:41:29 UTC No. 16583906

>>16583902
so explain how I'm wrong you fucking faggot
or alternatively hang yourself

Anonymous at Wed, 12 Feb 2025 19:46:40 UTC No. 16583911

>>16583906
Gravity reaches very high. Even Pluto, which is 5.9 billion kilometers away from the Sun, can feel it. The reason why there "feels" like there's no gravity in space is because things are in orbit aka in freefall, but the force of gravity is basically the same

Anonymous at Wed, 12 Feb 2025 20:06:33 UTC No. 16583929

>>16583911
the force of gravity is proportional to the product of their masses and inversely proportional to the square of the distance between objects centers, is it not? so then the ideal burn rate should be proportional to gravity and inversely proportional to exhaust velocity, no?

Anonymous at Wed, 12 Feb 2025 20:15:32 UTC No. 16583933

>>16583929
in the surface of the earth, you are 6300km away from the center of the earth. therefore your r^2 is already extremely high and even if you ascend 100km you won't feel the difference.
this is why if you are in orbit and fire your rockets in the opposite direction of earth, you won't ascend at all.
it feels counterintuitive, but if you want to ascend when you are in orbit, you need to burn parallel to the earth, this way you aren't really fighting gravity but you are getting more kinetic energy which will transform into potential energy (aka you'll be higher)
ideal burn rate is inversely proportional to drag. without an atmosphere, it doesn't matter how much you burn, it just matters the speed you get. if you go too slow you'll fall to the planet and if you go too fast all that kinetic energy will transform to potential energy and you will reach escape velocity

Anonymous at Wed, 12 Feb 2025 20:20:07 UTC No. 16583947

>>16583933
that's not what OP's post implies
it's clearly a vertical acceleration from standstill on a non-rotating drag-free object that is not the earth
you must have autism

Anonymous at Wed, 12 Feb 2025 20:23:25 UTC No. 16583949

>>16583947
in that case refer to my previous post: >>16583697
the post you're replying to is simply explaining why >>16583900 is wrong. gravity isn't wealer at higher altitudes unless you're comparing the gravity on the surface of earth vs the gravity on alpha centauri

Anonymous at Wed, 12 Feb 2025 20:24:32 UTC No. 16583951

1 is impossibile and would destroy efficiency so 2

Anonymous at Wed, 12 Feb 2025 20:29:19 UTC No. 16583956

>>16583949
if it's enough to make the rocket go higher by the diameter of even a single electron then I am right

Anonymous at Wed, 12 Feb 2025 20:30:57 UTC No. 16583961

>>16583956
based "well, technically..." autism

Anonymous at Thu, 13 Feb 2025 11:38:55 UTC No. 16584615

>>16583448
Depends on a lot of stuff. If we're lifting off from ground, then burning straight up will make you go really high at first but then fall back down. Real orbits are just you falling down, but moving so fast sideways that you miss the planet by the time you reach "down". So you have to go up, then sideways. Once you're in a stable orbit, usually getting "high up" is done with a multi-burn maneuver like a "Hohmann transfer" or a "Bi-elliptic transfer". If we call the lowest point in the orbit the "periapse" and the highest point the "apoapse", then generally speaking periapse is the best place to burn to increase apoapse height and vice versa. So in these situations, an instantaneous burn at periapse is most efficient since it gets all your burn in at the most efficient time.

Anonymous at Thu, 13 Feb 2025 12:22:24 UTC No. 16584680

>>16583454
Yes, it's.

Anonymous at Thu, 13 Feb 2025 13:24:25 UTC No. 16584728

>>16583695
kek

Anonymous at Thu, 13 Feb 2025 16:48:10 UTC No. 16584875

>>16583949
>gravity isn't weaker at higher altitudes
Yes it is.

Anonymous at Thu, 13 Feb 2025 17:01:48 UTC No. 16584889

>>16583900
>gravity is weaker at higher altitudes so the gradually burning rocket goes higher
But the longer you are exposed to the gravity, the more accumulated force is applied on you. And when you just make one big burn, you get overall less exposed to gravity. But I guess once you are in orbit, you don't need to care about it. Not sure what is the most efficient way, maybe making one quick burn to the lowest possible orbit and then making minimum burns at perigee. So that would be scenario 2, it doesn't say there that you have to burn it constantly with the same rate.

Anonymous at Thu, 13 Feb 2025 18:48:00 UTC No. 16584975

>>16584889

Anonymous at Thu, 13 Feb 2025 19:41:05 UTC No. 16585035

>>16584975
why is vgrad=1.2v0?

Anonymous at Thu, 13 Feb 2025 20:09:05 UTC No. 16585051

>>16584975
I'm not sure where you got [math]v_{grad} = 1.2v_0[/math]. Maybe that makes sense for some suborbital dynamics reason. It doesn't seem to take into consideration the Oberth effect. If you're already in a stable orbit, you end up with

[math] E = KE + PE = \frac 1 2 mv^2 + mgh[/math]

Notice that the kinetic energy of the system is quadratically related to the speed. If at 1 meter per second you have 1 Joule of kinetic energy, then at 2 mps you have 4 joules of KE, at 10 mps you have 100 Joules KE, etc. Thus, [math]\delta v[/math]spent burning in the direction of travel when you're going fast is more effective at increasing the energy of the system than [math]\delta v [/math] spent when you're going slow. So you want to burn as much delta v as possible when you're at periapsis, where your speed is the highest. This is why people usually transfer to higher orbits using Hohmann or Bi-Elliptic transfers, where you do short powerful burns at periapsis to bring your apoapsis up, then at apoapsis to bring your periapsis up.

The potential energy is linearly related to height and generally speaking most of the kinetic energy you get burning at periapsis is converted into gravitational potential (i.e. height) when you're at apoapsis.

Learn orbital mechanics. Play Kerbel Space Program.

Anonymous at Thu, 13 Feb 2025 21:37:21 UTC No. 16585119

>>16583949
>gravity isn't weaker at higher altitudes
The absolute state of /sci/. Why do I keep coming here when it's gotten to this point? This place used to be a hub of disaffected geniuses who solved the riemann hypothesis in their basements but were too lazy to publish it. Now the entire user base is like this anon, who doesn't even have a middle school understanding of science, but posts with a confident facade of expertise. Every post is like this, so I don't even know why I'm triggered by this one in particular. I just can't take it anymore.

Anonymous at Thu, 13 Feb 2025 21:39:28 UTC No. 16585121

>>16585119
I already explained that's an approximation chud. you won't feel the difference in gravity in the surface of the earth vs in the iss

Anonymous at Thu, 13 Feb 2025 21:42:02 UTC No. 16585123

>>16585035
it's an approximation

Anonymous at Thu, 13 Feb 2025 22:37:59 UTC No. 16585206

>>16583454
>>16583462
that mistake is typically made by native speakers because its and it's sound the same, so probably not ESL

Anonymous at Fri, 14 Feb 2025 11:50:22 UTC No. 16585685

>>16583454
Rockets are more fuel then not.

Anonymous at Fri, 14 Feb 2025 12:19:45 UTC No. 16585696

>>16584975
>disprove
I would like to introduce you to the Hohmann transfer orbit.
Also known as rocket only go up cause air hard.
>evaluates 10 second flight
>drops the 10 seconds
>arbitrarily gives the gradual burn 98 m/s additional delta V

Anonymous at Sat, 15 Feb 2025 00:30:14 UTC No. 16586192

Depends on the atmosphere. With no atmosphere, then scenario 1.

Anonymous at Sat, 15 Feb 2025 00:31:18 UTC No. 16586194

>>16584615
The question only asks about how of an altitude you can reach. You don't want to orbit.

Anonymous at Sat, 15 Feb 2025 11:09:09 UTC No. 16586528

>>16583448
1 goes higher because no gravity losses.

Anonymous at Mon, 17 Feb 2025 11:31:21 UTC No. 16589106

>>16583448
depends on the atmosphere density
in scenario 1 rocket has higher thrust to weight ratio so loses less energy to gravity losses but because it reaches max velocity at the lowest altitude it has greater loses (than 2) to aerodynamic pressure

Anonymous at Mon, 17 Feb 2025 12:47:44 UTC No. 16589195

>>16583448
Scenario 2 as it's not in a gravitational field.
QED

Anonymous at Mon, 17 Feb 2025 12:49:17 UTC No. 16589196

>>16585685
Why call it a rocket if it's mostly fuel?

Anonymous at Mon, 17 Feb 2025 13:05:14 UTC No. 16589209

>almost 40 replies
>1 mention of the Oberth effect
this board is beyond saving

Anonymous at Mon, 17 Feb 2025 13:46:30 UTC No. 16589231

>>16583448
It can be parameterized in such a way that either case holds.

Anonymous at Mon, 17 Feb 2025 14:33:41 UTC No. 16589248

>>16583448
the first scenario is called an "explosion" and it leads to loss of the vehicle so nothing constituting a rocket gets any altitude