What would happen if...? my son asked - I dunno!

[mental4astro (Alexander)]

Hi folks,

My son (9 years old) today asked me a question that I had no idea the answer to:

What would happen to a paper plane, if it was launched from the International Space Station into Earth's atmosphere?

Now, the dilemma for me is would its design and material structure see it burn up like meteor?

Would its design and material see is crumple up and slow down to a flutter?

It's not like the density of a paper plane would allow it to behave like a stone. It has a massive surface area by comparison too. Sure it is initially moving at some 20,000km/hr, but...

I honestly just don't know what would happen to the paper plane!

Any ideas?

[glend (Glen)]

Google provides a couple of examples of experiments conducted on this very topic. Just search on ' paper airplanes in space'. Can't provide links on the device I am on at the moment.

[jenchris (Jennifer)]

It would be tracked by the American Air Force and they would fire a missile at it.
Silly question really.

[mental4astro (Alexander)]

Thanks for the suggestion, Glen.

I found this very same question being answered in this link:

https://www.reddit.com/r/askscience/...per_aeroplane/

It is a curious situation. Be it launched from a geostationary situation (ie, from 0km/hr), or from the ISS, it would seem that due to its low mass, surface area, relative low density, and thinness of the atmosphere, etc, the plane would be slowly slowed down from its high velocity (if released from the ISS), and just flutter down, without burning up. Unlike, say, the Shuttle, which has a tremendous mass, bulk, and high density. I suspected something like this, but was not sure.

It should be noted that as the ISS is already travelling at a high speed, the paper plane would already be moving at that same speed, and with no atmosphere around it, it would not be crumpled. But, accelerate a paper plane from 0km/hr to 20,000km/hr in bugger all time, then yes, it would crumple, even if there was no atmosphere as the force it would be subjected to, the structure would not be strong enough to maintain the shape.

Some intrepid people did launch a paper plane from a high altitude helium balloon, some 90,000 feet, and it just 'flew' to Earth, undamaged. They even attached a camera to it to film its decent. Cool.

[DarkArts]

Hi Alex,

I'm going to go with burn up and disintegrate.

On leaving the ISS the paper will be travelling at around 7.6 - 7.9km/s. It will have to drop from ~400km to ~120km before there's sufficient air to deform and really decelerate it. Assuming it gets into a suitable trajectory for re-entry (and I'll leave the orbital mechanics alone), during the decent, the rarefied air at the reentry interface will be struck with such energy as to ionise molecules and generate enormous heat even for a piece of paper. G forces will (probably) be significant (regardless of low mass/density, and depending on trajectory) and the paper will crumple and disintegrate (ultimately like being blasted with a blow torch).

The Register has a project (called LOHAN) to release a "paper" plane from the edge of space using a helium balloon, but that's nowhere near the altitude of the ISS and not moving at anywhere like those speeds, so very much less energy will be dissipated.

Also see this: Why Didn't Baumgartner Burn Up on Re-entry?

[mental4astro (Alexander)]

Thanks darkarts. I can see both scenarios being correct, but which one ultimately is?

Need to make a phone call to the ISS and have one of 'em chuck a plane out the airlock! Anyone got their number?

[DarkArts]

Well, at geosynchronous orbit, velocity relative to earth is not 0, it's 3.07km/s. Similarly at ISS orbit (~400km) speed is very high, actually, counter-intuitively, higher.

There is a "feathered entry" technique for a suborbital vehicles that can dissipate more energy early in thinner air, but that is well, well below orbital speed. It's mostly about the kinetic energy of orbit being dissipated through friction.

Letting a paper plane "out the hatch" of the ISS isn't going to achieve anything, though, as the plane will stay in orbit close to the ISS (drifting slowly away with whatever differential velocity it was given).

Edit: A 10g sheet of paper will have ~288kJ of kinetic energy to dissipate during reentry from an initial orbital velocity of 7600m/s. Paper's specific heat is 1.336 J/g, so without cooling, temperature rise will be 216,000 deg C. I don't know what the radiative/convective cooling will be (heat radiated away to space as it 'glows' while heat is also transferred to very thin air) but since everything else during re-entry can't cool itself anywhere near fast enough to stop getting white hot, I'm going to go with the paper plane temperature rise being extreme.

[DJT (David)]

100 years on from General relativity.. E = MCsq?
iN the paper plane scenario, is it relevant?

[glend (Glen)]

Since there is no way to track a paper plane we'll never know what happens to it, and since a vast part of the earth is covered by water even if it makes it down it may never be found. Schodingers Cat comes to mind.

[el_draco (Rom)]

Originally Posted by mental4astro

Thanks darkarts. I can see both scenarios being correct, but which one ultimately is?

Need to make a phone call to the ISS and have one of 'em chuck a plane out the airlock! Anyone got their number?

Well, a bit of dust is light and small but it would burn up so i am with the charcoal scenario. Doubt it would "burn" as such because there is bugger all oxygen up there, but it would surly char away and disintegrate. A child who asks questions, well done!

[RobF (Rob)]

Its a shame you're not asking about the Mars scenario Alex. Would have been a lot easier for Mat Damon to pop a paper plane out of his non-existent removed windows for this experiment (ala "The Martian")
Top marks to your son though for coming up with such a decent conundrum!

[inline_online (Dan)]

Hi Alexander,

I've no idea what would happen to the plane but I want to comment on your son. I think it is wonderful that he has asked such a question to you. To me it shows imagination and willingness to learn and with those two things he will go far.

My youngest son, Lucas, is a bit like that. A few months ago he asked me "Dad, if we stretched the Earth out till it was the size of a piece of string, how long would the string be?"
I loved this question and it was a great oopportunity to show hm that maths is important and does actually have some uses. We made some assumptions (the string would be 1cm in diameter, the earth was spherical with 12,756 km diameter) and used very simple maths formulae to determine the answer. He was really engaged by it.

Your son may like the 'Wait, But Why' website if you haven't heard of it already. Lots of great hypothetical stuff on there to engage an inquisitive young (and older) mind.

Cheers,
Dan

[jenchris (Jennifer)]

Next question is using Avagadros number, estimate the number of molecules of oxygen in the atmosphere ...

[mental4astro (Alexander)]

Thanks Dan, for your comments. My son rattles off questions just about non-stop. I make every attempt to answer them without being condescending, and with as much technical input as I feel he can take. I love it, but his mum can't deal with the barrage of questions! Maybe its the answers she really can't deal with,

In reality, we don't need to retrieve the plane. All it needs is a transmitter, power supply and one or two sensors. The sensors could just be a thermometer - we really just want to know if it is burning up or not in the main instance. If it burns up, we have a result. If it doesn't, we can initially assume it has survived re-entry.

Other sensors could be an accellerometer and something to gauge the dimensional stability of the craft to determine if it is keeping its shape or crumpling. The accellerometer could be determined by monitoring the transmission through GPS, or something. None of these sensors as components are very big, and an appropriately designed and size of paper plane would not be difficult to build.

I happen to recall earlier this year about an Australian father and son team who have started a business of light weight rockets, and deploying sub-orbital and low orbit science payloads. Some of these were also something like 'paper planes' that had sensors on them, some type of 'nano-bots', that fluttered down. Reason I mention this is the 'paper plane' notion is really not that crazy and pointless.

If I only could remember the details of this father and son team. I think they are in South Australia. I wish I had paid more attention to the radio that day.

[mental4astro (Alexander)]

Found them!

Project Thunderstruck!

[bugeater (Marty)]

Ignoring the problem of how you de-orbit it, a lot of potential and kinetic energy needs to be dissipated in some way to allow it to come to earth. The only real way this will be done is via atmospheric drag/heat. So unless it can come down extremely slowly in a very large number of orbits so it can dissipate the heat through radiation faster than the drag creates it, I suspect it will heat up in the atmosphere and incinerate.

That's my guess anyway

[jenchris (Jennifer)]

Oxidation may be less likely than just incandescense and destabilisation of the celllulose. The effect of striking molecules at 17,000 mph is likely to be catastrophic to the plane and it would probably evaporate in a flash of plasma ionisation.

[blindman]

Very bright boy.
What would you tell him if he ask - who created the Earth?

[N1 (Mirko)]

I think if there was a surface area : weight ratio at which a feathered entry from orbital speeds would work (e.g. by using huge parachutes), I'm sure it would be a common technique already.

[andyc (Andy)]

Alex, your son's original question is perfect for XKCD "What If..."

And Randall Munroe's 'What if' book might be an excellent Christmas present for an inquisitive mind, exploring such ideas as a Diamond impact, the classic Hair Dryer experiment, and Interplanetary Cessnas (aka "Venus is a terrible place"). It was one of my favourite presents in years