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I have a humanoid individual who for various reasons finds themselves in low orbit 💫 with no ship or shuttle 🚀 or tech to take them down

The society they come from is about renaissance era level (but there are lost and hidden caches of far-future type knowledge - so I can get my individual to accidently find any of the required info).

What is the absolute minimum sort of facts that this person will need to know beforehand, to survive re-entry and the fall from low-orbit?

They have an oxygen supply and an advanced handwavium designed pressure-protection body-encasing substance. This substance can reflect heat, so I don't see any issues from re-entry itself(if re-entry is even an issue). This substance may possibly be suitable to propel small distances by directing the oxygen supply like retro-rockets. The substance can be altered in a short time to any basic shape the individual would require.

I will edit further if more clarification is needed.

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  • $\begingroup$ Is your individual flying in a stable orbit at the start of this fall, or in a steady place above the surface and starting to fall straight down? The former would be a lot more challenging. $\endgroup$ – Cyrus Jun 22 '16 at 12:15
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    $\begingroup$ Worldbuilding is not a child's picture-word reading primer. $\endgroup$ – JDługosz Jun 22 '16 at 12:17
  • $\begingroup$ I was thinking that they would already be on the move. But not straight down - I can make it any angle that would be necessary. @JDlugosz, I do realise that, would be too easy if it was. Boring. But easy. That's pretty much why I'm trying to only ask things I'm having trouble with. And then just the basics :) $\endgroup$ – EveryBitHelps Jun 22 '16 at 12:28
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    $\begingroup$ If anything, I'd say the single fact you need to know to survive is "The enemy's gate is down." $\endgroup$ – Cort Ammon - Reinstate Monica Jun 22 '16 at 16:01
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    $\begingroup$ The one thing you need to know is how NOT to end up in a situation where you're magically falling from orbit. $\endgroup$ – iAdjunct Jun 22 '16 at 21:13
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Deorbiting is actually pretty easy, and doesn't even need a magic space suit.

You could provide him with something like the MOOSE, or even just the materials and a set of plans to build one, and he could safely fall out of orbit no problem.

Similar to this, the IRVE-3, which was originally proposed to NASA by Arthur C Clark, passed it's initial tests back in 2012.

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  • $\begingroup$ I was thinking something similar to the IRVE-3! It's a fairly simple shape to form. And also easy to explain to someone with that level of knowledge! And if Arthur C Clarke proposed it...who am I to say no :) $\endgroup$ – EveryBitHelps Jun 22 '16 at 20:01
  • $\begingroup$ I hadn't seen the moose before. But that looks pretty good to. I assume it uses the same or similar cone shape as the IRVE-3 for re-entry? $\endgroup$ – EveryBitHelps Jun 22 '16 at 20:06
  • $\begingroup$ @EveryBitHelps If I'm remembering the story correctly, ACC wrote a story back in the 80s where a character does something like this, and he talked to someone at NASA to see if it was possible. The MOOSE is really similar, if simpler. Some preliminary testing was done, but not to the same extent as the IRVE-3. Both of them fall into the "in case of extreme emergency" where the alternative is certain death. The blunt cone/shuttlecock shape is really good for this because the shape makes sure the ablative surface is pointing the right way. $\endgroup$ – AndyD273 Jun 22 '16 at 20:15
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    $\begingroup$ Plus I like the idea of saying "so, I guess I'm going to fall out of space riding a moose"... $\endgroup$ – AndyD273 Jun 22 '16 at 20:17
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It depends on the suit's capabilities

The OP doesn't talk about how this renaissance individual got into orbit. If they are not orbiting then the problem is solved for them already; they just fall out of the sky. Surviving reentry depends completely on the design and capabilities of this suit. If this individual does nothing, they die. If the suit fails at any point before touchdown, they die.

This individual will need to know the following:

  • Their direction of travel (easily observable by looking down at the planet below)
  • How to fire the suit's maneuvering thrusters (how easy this is to do will depend on the user interface of the suit)
  • To fire the thrusters opposite the direction of travel. They don't need to know about orbital mechanics or aerobraking or anything else.

Assuming the suit is capable of surviving re-entry (which I'm very impressed by) and can keep the individual alive through the entire envelope and an automatically deployed parachute for final descent, this individual should survive.

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  • $\begingroup$ Nice. Thanks. So I pretty much just got to get my individual to read up on parachutes. Who said the 'suit', as you called it, was designed by renaissance level tech? The substance is probably made up of applied phlebotium. You could probably see my handwaving all the way from low-orbit! $\endgroup$ – EveryBitHelps Jun 22 '16 at 14:00
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    $\begingroup$ Just to point out that someone has already done this, from a good fraction of the way to low earth orbit (about a quarter of the way to be exact), with today's technology. I can't think of a reason why four times the height would make a substantial difference to the result. $\endgroup$ – DJClayworth Jun 22 '16 at 15:22
  • $\begingroup$ @DJClayworth There's a huge difference between just falling from LEO and deorbiting from LEO. Brave Felix was falling, not deorbiting. The tech required to kill off 7.8km/s for a human sized object is radically different than just keeping someone alive till the parachute opens. $\endgroup$ – Green Jun 22 '16 at 15:42
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    $\begingroup$ @EveryBitHelps I'd have the suit automatically open the chute. Parachutists require lots of training and experience before they are allowed to jump alone. It's incredibly easy to mentally lose it during a jump. This individual is highly unlikely to know how or when to deploy the chute. $\endgroup$ – Green Jun 22 '16 at 15:49
  • $\begingroup$ It's because of brave Felix that I know the idea of falling from low orbit is doable with today's tech. But I'm pretty certain he took a bit of time to research how to fall before actually falling. Nothing like killing yourselves while being livestreamed to millions of viewers! $\endgroup$ – EveryBitHelps Jun 22 '16 at 16:26
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Assuming a relatively small oxygen supply and a total effective suit density greater than water, the astronaut will need to be able to roughly figure his reentry duration so as not to fall into the middle of the ocean. Since his suit is denser than water he'll sink to the bottom, and although the suit might protect him from high pressure as well as vacuum (handwavium, remember?) it's going to take him a long time to walk to shore.

So he'll need his orbital speed and altitude, as well as the delta-v his reentry thrusters will produce. Using these he can calculate his nominal fall deceleration, his fall time, and the lateral distance this fall will cover. The actual distance will be less than this, since his aerodynamic braking will also reduce his lateral velocity, but it sets a limit to how far he has to look ahead before deciding to fire his thruster.

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