No Stupid Questions

2278 readers

1 users here now

There is no such thing as a Stupid Question!

Don't be embarrassed of your curiosity; everyone has questions that they may feel uncomfortable asking certain people, so this place gives you a nice area not to be judged about asking it. Everyone here is willing to help.

ex. How do I change oil
ex. How to tie shoes
ex. Can you cry underwater?

Reminder that the rules for lemmy.ca still apply!

Thanks for reading all of this, even if you didn't read all of this, and your eye started somewhere else, have a watermelon slice 🍉.

founded 2 years ago

MODERATORS

[email protected]

Parachute maximum limits? ISS parachute to earth? (hackertalks.com)

submitted 1 month ago by [email protected] to c/[email protected]

5 comments fedilink hide all child comments

The astronauts on the ISS that are stuck and can't parachute back to Earth... but why not?

The highest jump I could find was 39km (Stratos jump)

Is it the height from the planet? The speed of the ISS? If we wanted to design ISS escape pods, what would be required?

you are viewing a single comment's thread
view the rest of the comments

[–] [email protected] 3 points 1 month ago

The others already gave the reasons, but let me put some numbers to those answers. When I jump out of a plane, I get about a minute of freefall. That's because terminal velocity for skydivers usually is ~115-135mph, or 200ft/s. That speed comes when you're flying on your belly, putting about as much drag as possible in the wind. If you're in other positions, like head down or feet down, you can get going much faster (record for head down is over 300mph).

At ~120mph, the jolt from pulling a parachute is pretty good. We use specially designed rigs to actually slow the parachute's opening, so the jolt isn't terrible. When the designs don't work, it can cause injury or even death. That head down record I mentioned earlier? If you pulled at that speed, you are almost guaranteed to suffer major injury. It's why we recommend that skydivers DO NOT learn to do so until they are pretty experienced. There are even more specialized rigs to fly in those positions that ensure accidental deployments of the parachute are next to impossible while at those speeds.

Now, to have a stable orbit in space, relative velocity is vastly larger than even in freefall. If I remember, it's closer to 20,000mph (I think the ISS crew experience a 'sunrise' every 75 minutes). In order to get anywhere close to the safe parachute-pulling speed of ~120mph, you'll need to slow down a lot. Unfortunately, doing so is going to create (transfer if we're being physics specific) a great deal of energy in the form of heat, which will far exceed what they can safely handle. Don't forget that 2003's shuttle accident was because of damage to the heat shield of the shuttle, compromising its ability to keep heat from the crew compartment.