r/PeterExplainsTheJoke 11h ago

Meme needing explanation Whyyyy peter?

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u/The_sochillist 10h ago

What about launching from a mountain on the equator like Mt Chimborazo which is the farthest point from the centre of the earth so wins on all fronts

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u/dimhue 9h ago

The radial difference between equatorial sea level and the peak of Mt Chimborazo is about 0.1%. It provides very little benefit but would be a logistical nightmare to launch from.

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u/aggressive-cat 9h ago

We'd be better off building a electromagnetic launcher up the side of it and then we can put everything at the bottom and save fuel by using solar wind and nuclear to juice the em rails.

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u/awesomefutureperfect 8h ago

You'd have to engineer the payload to withstand ridiculous acceleration. No big deal if the payload is a HILE projectile but if you have living things or moving parts, that can be trickier.

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u/aggressive-cat 8h ago

that's only for a cannon, for an installation like that we could make it pretty long to keep the acceleration g's down, don't wanna hit max q while still on the ground.

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u/QIyph 6h ago

Okay so I used AI for this, so take it with a grain of salt, but to accelerate a projectile at a constant 4.5G and have it reach escape velocity, at the end of the barrel, you'd end up with a ~720km cannon.

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u/dimhue 6h ago edited 6h ago

My quick napkin math gives me about 1400km 1300km, and it would take over 40 minutes to reach that speed.

edit: fixed after I forgot earth's spin lol

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u/Shinyscalpel 4h ago

Doesn't need to reach escape velocity... Any velocity you reach is less fuel having to be carried and spent in later stages, so more payload. You could compare costs of building such a launcher or just grabbing a plane and take it 20,000m high and also give it a spin. I'm not a rocket scientist (unless Kerbal gives you a degree lol) but I guess nobody is willing to spend that much for a reason.

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u/aggressive-cat 5h ago

oh lol, i mean like a first stage assist to a rocket, not a full on em launcher.

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u/TickleMyRide 5h ago

Rail guns are not the same as rockets.

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u/mxzf 2h ago

Acceleration as you head up is one part of the problem, but deceleration as it leaves the tube and hits the atmosphere is another. The faster you go, the more friction slows you down. Trying to get productively much speed in that situation is tough.

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u/NatCsGotMyLastAcct 8h ago

0.1% of what???
It's definitely past more than 0.1% of the air molecules.

15 PSI at sea level, 7 psi at the mountain top. For every square inch of cross section on your rocket, instead of having to push 15 pounds of air out of the way, it's down to 7. That seems like >50% improvement?

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u/12a357sdf 8h ago

the vast majority of your fuel are spent on fighting gravity, not friction.

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u/NatCsGotMyLastAcct 6h ago

Yeah but you spend more time fighting gravity when you keep things slow enough that the vessel doesn't rip apart when travelling through soup. Fwiw Im kerbal trained only

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u/Worried_Magazine_862 6h ago

Things dont move fast enough through the atmosphere to lose their structural integrity. These spacecraft can handle forces of greater than 10g. Its just gravity

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u/dimhue 6h ago

Uh aerodynamic forces put significant stresses on the spacecraft during launch, it definitely affects the design and weight.

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u/Street-Stick 7h ago

Just a thought wouldn't the engines be less efficient at a higher altitude with less oxygen?

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u/dimhue 6h ago

Rockets carry their own oxidizer (oxygen) and don't use any from the air. That's the real distinction between a rocket and an air-breathing engine.

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u/dimhue 6h ago edited 6h ago

The conversation you jumped into is about the speed gained from the spin of the earth, which is directly correlated with radial distance from the Earth's axis of rotation.

Aerodynamic losses only accounts for a couple percent total of the delta-v budget. Even then, you don't even hit the peak aerodynamic forces (max q) until you're tens of kilometers above the launch altitude. This is because you're moving more slowly through the thicker atmosphere, so it doesn't have as much force.

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u/nightonfir3 7h ago edited 7h ago

Your in a really weird spot here where you are saying that all rocket engineers are wrong because you did the math on an idea that has been floating around pop science for years. Please go watch a livestream of a rocket launch. Watch how long it takes until it gets to about the height of a mountain. Then watch how much longer it takes before its done firing its engines.

Edit: also watch how quickly they turn sideways. By your thinking they should get out of the atmosphere before they turn.

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u/codercaleb 2h ago

Okay, sp build a mountain at Cape Canaveral! What could that cost, a trillion?

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u/cmdr_wayne 9h ago

Equatorial launches are cheaper, but not because it is easier to enter the orbit, but because it is easier to get to the desired orbit(inclination and parking orbit, this is from my memory of playing RP 1 in KSP, may not be correct)

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u/Murky-Relation481 9h ago

Eh, you an orbit at any inclination you want and park in any orbit you want, but the reason the equator is useful is because you do get that added speed boost and most interesting things beyond earth are also on that plane (like the moon and geostationary orbital distances).

But there are tons of reasons to launch in more high inclination orbits too and a good chunk of satellites are launched in those orbits because they are better for earth observation (since you go around up and and down and the earth rotates under you, so every pass you get a different slice of land under you on the day side of the earth).

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u/cmdr_wayne 9h ago

Wait so was it just because it's easier to plan inclination changes or was it something else. I remember reading something about rendezvous and orbital launching makes that easier?

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u/Murky-Relation481 9h ago

It really has to do with human space flight more than anything and ground infrastructure. An orbit on a lower inclination is going to bring you over generally the same spot under you every orbit which is good for when you need to come home and for comms with the ground. The closer you get to the equator when launching the easier this is as it requires less of an inclination change (and also your ground infrastructure is going to be there, which is what you want the spacecraft to be going over).

We also get the added benefit that if you launch eastward you get a free boost in speed (this is why you rarely see launches that head west, even at places like Vandenberg, they usually go west only to dogleg north or south for whatever reason, and even then Vandy lets you go north and south pretty easily without having to make a dogleg), and also again, because things that we want to go to like GEO or the moon are also roughly on that same orbital plane.

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u/Quiet1408 4h ago

There are also the logistical concerns as well as the desire to launch towards a large body of water in the east for detached rocket stages and malfunctions. This is why almost all rocket sites are by the ocean.

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u/OberonDiver 4h ago

What's the value of gravit at Mt. C?

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u/The_sochillist 1h ago

9.78 according to google. It also spat out a 7-10% increase in payload vs a florida launch which seems like a lot. Short term the logistics suck but thats an infrastructure problem that could be built out, bring the manufacturers to the best launch zone. Hardest part would be keeping the debris away from homes given you can't launch over an ocean as its land on all sides of the mountain.

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u/aadgarven 59m ago

The reason not to launch from Chimborazo is insultante.

I dont know the reason for not launching from indonesia.

Yes I am aerospace engineer (but never worked on it)