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

[mental4astro]

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? :shrug: :question:


190539

[glend]

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]

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

[mental4astro]

Thanks for the suggestion, Glen.

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

https://www.reddit.com/r/askscience/comments/2l8waf/what_would_happen_if_you_threw_a_pa 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 (http://www.theregister.co.uk/science/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? (http://scienceblogs.com/builtonfacts/2012/10/16/why-didnt-baumgartner-burn-up-on-re-entry/)

[mental4astro]

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

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]

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

[glend]

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]

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]

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") :D
Top marks to your son though for coming up with such a decent conundrum!

[inline_online]

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:D) mind.

Cheers,
Dan

[jenchris]

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

[mental4astro]

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! :lol: Maybe its the answers she really can't deal with, :question: :lol:

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]

Found them!

Project Thunderstruck! (http://projectthunderstruck.org/)

[bugeater]

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 :D

[jenchris]

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]

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]

Alex, your son's original question is perfect for XKCD "What If..." (https://what-if.xkcd.com/)

And Randall Munroe's 'What if' book (http://whatif.xkcd.com/book/)might be an excellent Christmas present for an inquisitive mind, exploring such ideas as a Diamond (https://what-if.xkcd.com/20/) impact, the classic Hair Dryer (https://what-if.xkcd.com/35/)experiment, and Interplanetary Cessnas (https://what-if.xkcd.com/30/) (aka "Venus is a terrible place"). It was one of my favourite presents in years :)

[ChrisV]

This question brings back the horrors of my son doing the HSC over the past few weeks !!!!

He did physics and virtually the same question was in a past paper that he did for practice, except it was something heavier. And one object was released from a moving space station over the equator. And another dropped from one at the same height over the pole.

Ahhhhh. Chris

[Neutronstar]

Alex,

I wondered if you have shown your son Felix Baumgartner's Space Dive?
There is some video's of it on Youtube and a NatGeo documentary on Netflix - called "Space Dive".
While this is not as high up as the ISS it is close to the edge of the atmosphere.

I kind of imagine that he and his space suit made it that the paper plane would as well.

Tim

[pluto]

Apart from the difference in altitude, Felix wasn't travelling at orbital speed which for the ISS is about 27600km/h.
Even an orbit with it's apoapsis around that of the ISS and its periapsis within the atmosphere would still have a velocity of over 27000km/h and Felix only reached a top speed of ~1300km/h.

Good doco that one on Netflix though, very interesting :)

As for whether the paper plane would survive, I think it would burn - there's just too much energy to dissipate - but I don't have the knowledge to answer that using physics.
However if one was able to control the planes attitude then maybe there would be a way to slow it enough slowly enough by skimming, or bouncing, off the top of the atmosphere multiple times before actually re-entering. Then again probably not as there are good reasons why the Shuttle never did it that way.

[mental4astro]

I'll show him the space jump, for sure.

I've been thinking about the re-entry scenario some more. While my maths may be a little, well, wanting, logic is helpful...

Momentum is a function of mass and velocity, and a cousin of kinetic energy. Take the recent Russian (?I think it was?) satellite that was in a decaying orbit and eventually re-entered. It had a huge mass, and not a streamlined structure. High altitude drag was what was slowing it down. The burn up did not happen until it reach a certain altitude where the density of the atmosphere overwhelmed the heat dissipation that the very thinnest of the atmosphere would have been generating. But because of its momentum, this slowing of the orbit was very gradual, but drag would have eventually slowed it enough to for it to fall into the denser atmosphere, but not enough to slow it significantly enough, and it burnt up.

Now take a paper plane. While it is moving at the same rate of knots, its momentum is considerably less as its mass is tiny. And, as a function of its surface area, the drag it would experience at the same altitude of the thinnest of the atmosphere, the effect on the plane's momentum would be significantly greater than the above satellite. The result would be a much faster rate of deceleration than the satellite, yet it is still at the very highest and thinnest levels of the atmosphere. It would slow down faster. But it would also not be dropping down through to denser atmosphere either. Drag would also serve to slow down its vertical decent. It may well be that the plane just does't burn up.

It could well be that the initial drag may have a catastrophic affect on the structure of the plane, and there may be some ionization effects, but I somehow doubt that it would incinerate.

The proverbial 'dust' particles that burn up on re-entry have a couple of things going against them - Their mass to density to volume ratio is greater than a paper plane; They enter the atmosphere at a steeper angle than the plane would, even for those that are skimming the atmosphere (the plane is initially running parallel to the atmpsphere).

Now, all of this is all just hypothetical. Everything that is written here is!

What we really need is someone to hurl a plane out of the goddamn ISS airlock! :tasdevil:

Thank you for the discussion, girls and boys. I am enjoying the debate, :)

[sharptrack2]

One aspect that stands out in my mind is that there would be no shock wave in front of a paper airplane... assuming standard "dart" folding. Therefore, no matter what speed, the heat build up would be greater than can be dissipated and the plane would simple turn to ash as fast as it could enter the upper atmosphere. I don't think that there would be enough structural strength to withstand a "flaring" manoeuvre and the plane would always present a knife edge as it fell toward the earth.

I found a very interesting document on the FAA website, on re-entry design...

https://www.faa.gov/other_visit/aviation_industry/designees_delegations/designee_types/ame/media/Section%20III.4.1.7%20Returning%20f rom%20Space.pdf

[jenchris]

The structure of paper means it would be dismantled quite quickly by molecules that have a relative velocity of 17500 mph.
The resulting strands of cellulose would be heated by impactas they swapped v for heat. The temperature rises to white heat quite quickly and destruction to molecular level dissipates the remains

[mental4astro]

Thanks for that link, Kevin. Interesting read.

Combining the information of that FAA link, and the high velocity impact of the air on the material structure of the paper as mentioned by Jen, I know see that a paper plane would not survive re-entry if its initial velocity is the same as that of the ISS. There is just too much energy involved and the paper is too fragile.

Now, a 'geo-static' re-entry, that is, the plane's relative velocity to Earth is 0m/s, a simple lift and drop, that's another matter.

Thanks for the discussion. I'll now present this info my son :)

[N1]

That's got to depend on the distance from the surface. And to a certain degree (no pun intended), latitude. While perhaps not a great factor at astronomical speeds, the Earth's atmosphere does move at about 460m/s at the equator at ground level releative to a fixed point in the sky (fixed relative to background stars), even more at higher altitude. Obviously that's not the case for geosyncronous objects, but for them, altitude is just as cricitcal.

I'm suspecting any wisdom derived from high altitude balloon flights tells us very little in this regard. Baumgartner for instance was nowhere near space. His ascent relied on the very thing that makes the Earth's surface a "non-space" environment. Give an object enough time to be accelerated by Earth's gravity in a negligible atmosphere and see what happens when it does hit the air...

Edit - I just re read the original question. A geostationary/syncronous paper object falling from ISS altitude very well could survive I suppose.

[RobinClayton]

I love this debate so far.

My vote is for the paper plane to survive "intact". One problem is that the ISS is in orbit, so anything released from ISS would also be in orbit. However if it was thrown towards Earth, then it should eventually reach the outer atmosphere. Here I think it should be slowly drifting downwards and friction would not build up sufficiently to damage the paper. The shape of the plane may start to crumble, but not until much lower altitude.

If you are able to contact ISS, then you may want a controlled experiment with several planes of different shapes and thrown in several different directions. Do we know how much paper they have on board?

[pluto]

Knowing what direction to throw the plane from the ISS to de-orbit it is easy - throw it in a backwards direction to reduce its orbital energy and lower its periapsis (opposite to the direction of travel). You would have to throw the plane at a relative velocity of over 300km/h if you wanted it to re-enter on the current orbit, however a paper plane in an orbit similar to that of the ISS will de-orbit, due to atmospheric resistance, after a couple of weeks(?) anyway.

A few years ago a cosmonaut hit a 3 gram golf ball from the ISS in a direction opposite to the direction of travel. A super quick google hasn't found much detailed info but it would be interesting to see if there's any data on what happened (though I know it was too small to be tracked by radar).

I like the thinking in your latest post Alex, but I still think that there's too much heat to dissipate and, to my highly untrained mind, I don't think a paper plane is a very good radiator of heat. It's gonna burn!

[mental4astro]

IF such an experiment could be allowed on the ISS, the simplest payload would be a "sheet of paper" and the smallest 'Sputnik' beep-beep transmitter possible - the primary outcome we want to know is 'Will the plane survive re-entry'. We don't need to retrieve it, and a beep-beep transmitter will allow ground based amateur astronomers and radio hams to follow its progress. If the transmitter survives, the plane's survived. Simple.

Then other scenarios could be looked at such as initial orbital speed, materials, plane design; many things.

Not a flippant idea either. A lot of money goes into designing re-entry mechanisms. Why not look at an idea from left field?

:atom: :anaut: :einstein: :rover1:

[bugeater]

I'm not sure it would reach the atmosphere. Throwing it towards the earth would put the paper plane on a different orbit to the ISS, but it would still stay in orbit, at least over the medium to long term (most stuff in low earth orbit will come down eventually due to atmospheric drag). You would basically put it on an elliptical orbit. Indeed, strangely, I think it would spend part of its orbit above the ISS now.

A fun way to play with orbit mechanics and indeed build space rockets is to purchase the game Kerbal Space Program. It's great fun.

[N1]

I don't think throwing anything (as in: using your arms) from the ISS, regardless of direction, would provide that object with a trajectory sufficiently different from that of the space station itself to allow a scenario that was different to the fate of the ISS if left to drift. Even the fastest cricket bowl is mind crushingly slow compared to the 8km/s of the ISS. The object would deorbit and burn up. A little sooner or a little later, depending on direction.

Also the fact that it's a paper plane (as opposed to an unfolded sheet of paper) would appear to be counter productive when we want the piece of paper to spread its energy over as large an area as possible. The plane's streamlined shape might make it travel much faster into and through the critical area than it otherwise would.

[pluto]

I agree. As mentioned previously the paper plane, or anything else on an orbit similar to the ISS, would need to decelerate by over 300km/h to enter the atmosphere at the next periapsis.

[mental4astro]

Flight stability - One thing I don't think the plane will do is be gliding in a steady, nose-first direction, when released from the ISS. I think it will be tumbling, even if only slowly - air flow over the plane is what keeps it stable. So to my mind it will initially be behaving like a sheet of paper. I don't think it will achieve a nose-first steady flight position until air density becomes high enough, and then the plane's design needs to be such that it self-corrects. It is a good point you make, Mirko, ;)

Mind you, this could also be self defeating if it self-corrects too soon, :rolleyes:

[mental4astro]

Here's another curve ball: elevators on the wings?

As it enters the atmosphere, and drag takes effect, elevators on the wings would act to raise the nose and lift the craft. It's nose would then drop again, descend, and rise up again, doing a constant dip-and-dive action. This would also act to slow the plane.

Something more to ponder... :question:

[N1]

The wing nuts on here might be able to help, but I think it would depend on whether air density and air speed can be treated as being inversely proportional for the purposes of flying at these speeds, so that this familiar pattern could still occur. I also understand the speed would change periodically in this scenario and each lift and drop of the nose would depend on a certain air speed:air density ratio. Each lifting of the nose would require an increase in speed to occur first, and we'd have to ensure the preceeding deceleration from lifting the nose does not disrupt the paper craft by throwing it into some other position than what is required for the next cycle, or outright destruction. I'm also having trouble imagining how exactly it could even accelerate again once the atmosphere starts to slow it, but while it's still travelling at enormous speed. I'm thinking the plane's encounter with the atmosphere might not involve any acceleration at all, just a change in the rate of slowing - until the process is driven purely by aerodynamics.

[pluto]

This is what I was hinting at in my first post, but I think the plane would still burn up as it's unable to radiate the heat built up during each "dip" into the top of the atmosphere. From what I understand this is one of the reasons the Shuttle wasn't designed to re-enter this way, even though it would have resulted in a lower speed during descent into the thicker parts of the atmosphere.

[AstralTraveller]

Everyone talks about thing burning up in the atm but no one has mentioned that every day tonnes and tonnes of material falls to Earth from space. Dust-particle sized material can make it through the atm but something the size of a pea will burn up. So there is a size limit below which drag in the upper atm will slow the object soon enough to stop it burning up in the lower atm. However I doubt this will slow the paper plane enough - especially if it is loaded down with grams of sensors. Also, as Jen has noted, paper is more combustible than minerals.

A subsidiary question is, assuming the paper plane is on the night side of the globe, could the plane's demise be observed as a meteor?

[pluto]

The debris objects, both human-made and natural, that reach the surface after re-entering are what's left of a larger object that has partly, or mostly, burnt up. Nothing that I know of, except for the tiles on the Shuttle, X37B, and Buran, survive re-entry from orbital speeds or above without losing part of their mass through ablation.

[astronobob]

Just my 'Bobs' worth,

My 1st thoughts are I reckon it would survive in its entirety, sure, its not like it will hit the atmosphere at tremendous force, and it wouldn't be entering at a sharp angle, and not at the speed of a meteor.

The gradual 'almost horizontal' very low angle decent would see it gradually slow down due to a slow buildup of friction intensity over quite a long period of time - could be many hours, but definitely not instantly, Like a few seconds or few minutes even !
It would probably also transverse half the globe before it reached 50% of the atmospheric pressure, by then the greater gravity influences it and would fall/fly as fast/best as a paper plane can in the conditions and eventually return - 1 in 3 odds of it landing on soil to claim Guinness, Lol ?
I dont really know but there's my thoughts, , ,

Tho what about freezing, upper level moisture, through lower cloud ect, ??
If entering at a low angle, would it deflect off the atmosphere and land on mars and the rovers find it, Lol , yeah, i knew it, they left a note Lol