If you had to jump off of the space station with with your friends, and all you could bring with you were your spacesuits, parachutes for each of you, and you had a magic device that had enough oxygen
-
If you fall straight down so I guess that means straight down is still like 24000 mph or whatever the earth is rotating… but if you slow yourself down would you still burn up?
If you fell straight down from the height of the orbit of the ISS, by the time you reached the thicker parts of the atmosphere, you would be travelling at around 2 km/s. Unprotected, this is enough energy to raise your temperature by 500 °C, but not all of that energy would actually go into you so you would be a little bit cooler. But suffice it to say, if you have to get off the ISS without a capsule, you're cooked.
-
It seems difficult to have enough bottled oxygen to deorbit yourself, but maybe doable.
The MMU backpack units on the space shuttle had a total delta v of ~30 m/s. You need about three times that amount to deorbit from ISS. So imagine you need 3 MMUs give it take worth of expendable propellant oxygen, and you can do it. (The MMUs used nitrogen, but for this purpose oxygen is pretty much the same.)
After you deorbit, you will of course burn up on re-entry with no heat shield. But it might be conceivable to design a personal heat shield surfboard.
You could also avoid the whole burning up things by braking a lot more during the deorbit maneuver. But instead of 100 m/s, you need to slow down by more than 7000 m/s. That's quite a few more MMUs worth of gas. But if you do that, then you're essentially making a free fall jump from space, which has more or less already been demonstrated.
A freefall from space has not been demonstrated. The 40 km jumps done are well below the 100 km Karman line (accepted as the definition of space, but it's mostly an on-paper thing) and much lower than the 400-600 km orbit of the ISS. The thing about these jumps is they begin at ~0 km/h already in or just above where the atmosphere is significant. If you fall from significantly higher than this, you have a lot of altitude in freefall and the atmosphere is so thin that you won't slow down enough for it to matter, leading to a very high speed entry into the lower atmosphere.
Baumgartner's top speed was Mach 1.25. If you fell from the ISS, your speed when you got to where he began his fall would be around Mach 6-8.
-
Right but we have the oxygen. Which direction should we jump? If we jumped forward we wouldn’t run into it again but we could get further away faster if we jumped away I think
Orbits are all about speed, not height. To deorbit, you need to reduce your speed at the highest part of your orbit. This will lower the lowest part. You jump off the back. You would need to jump FAR harder than your legs are capable of though.
Unfortunately, the sheer speed will kill you, without shielding. As you hit the air, you are going so fast, the air can't get out of your way. You compress it ahead of you, that heats it up. It gets hot enough to melt most metals. The air will cook you, long before you get slow enough to use your parachute.
For comparison, terminal velocity (max speed you reach falling) is around 200km/h. Orbital velocity is 7km/s or around 25200km/h.
-
The weight of the device let’s say is 20 bananas and so that makes 2 fit astronauts and a stoner. Nobody knows why the stoner was on the space station to begin with.
20 bananas
Americans will truly use anything but the metric system
-
for you to survive the journey. If you could somehow spray the oxygen to get you close enough to Earth to use the parachute and land safely, how would you do it?
You're going much too fast to hit the earth, you'll miss it and continue in orbit. To deorbit, you'll need a lot of things to throw in the other direction, like the oxygen from your magic tank. You'd need about a full rocket full of oxygen (~170 tons) to slow down, probably more because the exit velocity would be slower than a rocket.
The other issue with this scheme is you'd slow down too slowly. You'll start getting slower and lower, but you'd start to get into the atmosphere, which because you're still going so fast would cause you to not have a great time. So your magic oxygen bottle will also need a massive tube off the end of it, maybe a couple meters in diameter.
But if you had your magic infinite air tank with a huge tube off it, theoretically you could get back down to earth safely with just it, a space suit, and a parachute.
-
Do rockets aim straight up as they try to leave earth, why don’t they burn up on exit too
By the time they're going fast enough, they're high enough they don't have much air to worry about. (And they do have an angle over too, not just straight up)
Missiles do go more or less go straight though the atmosphere horizontally. Most are slower than what we're taking about, but hypersonic missiles get close to rocket speeds. And they do need big heat shields to keep from melting immediately.
-
for you to survive the journey. If you could somehow spray the oxygen to get you close enough to Earth to use the parachute and land safely, how would you do it?
If you just stepped outside of ISS you'll still be in an orbit around earth ( something something first law of motion) it would take you decades to loose enough energy to deorbit and if you survived that long without eating drinking shitting then good luck surviving the reentry.
-
The only reason things burn up when they enter the atmosphere is because they're moving so fast that the friction from the air generates too much heat.
So yes, if you slow yourself down enough then you could just float down like a feather in the wind.
I have no idea how fast is too fast.
Minor nitpick, it's not friction, its compression. The air can't move out of your way fast enough, so you push it ahead of you, and as more air gets smooshed together, it gets hotter.
-
If you just stepped outside of ISS you'll still be in an orbit around earth ( something something first law of motion) it would take you decades to loose enough energy to deorbit and if you survived that long without eating drinking shitting then good luck surviving the reentry.
Is that correct? I know there's still a trace of atmosphere at the altitude the ISS orbits, and they need to occasionally make a burn to regain speed lost to friction.
-
Minor nitpick, it's not friction, its compression. The air can't move out of your way fast enough, so you push it ahead of you, and as more air gets smooshed together, it gets hotter.
Fair enough.
-
Is that correct? I know there's still a trace of atmosphere at the altitude the ISS orbits, and they need to occasionally make a burn to regain speed lost to friction.
At ISS altitude, it's probably not decades to decay, but a few years instead.
-
If you fall straight down so I guess that means straight down is still like 24000 mph or whatever the earth is rotating… but if you slow yourself down would you still burn up?
Orbiting is falling to earth, but going so fast sideways that you miss, forever.
-
System shared this topic onSystem shared this topic on
