Pic of the Shuttle reentry… from space!

By Phil Plait | February 22, 2010 1:45 pm

The Space Shuttle mission STS-130 ended last night with the Orbiter Endeavour safely landing in Florida at 10:20 p.m. Eastern time yesterday. I live-tweeted the event, and so I was too busy to pay much attention to the Twitter feed from Soichi Noguchi, an astronaut onboard the International Space Station. I wish I had, because then I could’ve retweeted a picture he took that is simply amazing:

soichi_shuttle_sturn

That’s Endeavour as it was over (I believe) the Caribbean Sea. At that point, it was still sloughing off the energy of orbit, dropping in velocity as it dropped through our atmosphere. To do that, it made two wide, curving, banking turns, called S-turns, that slow the Orbiter down. As it’s doing that, it’s ramming the Earth’s air at something like Mach 25, which violently compresses the gas and heats it up. This is what causes the Orbiter (as well as incoming meteors) to glow, not friction.

The more you know.

Anyway, the glow is bright enough to be seen in the Space Station, if it happens to be overhead at that time — and that doesn’t have to be the case; it depends on how long it takes after the Orbiter undocks from the ISS before it lands, for example. In this case, though, Soichi was on the ball, and snapped this shot of Endeavour while it was still glowing hotter than the surface of the Sun!

Like I said, amazing. As far as I know, that’s the first time this has been photographed from space. And we’ll only get four more chances… but after that, maybe it’ll be a Dragon capsule they’ll see.

CATEGORIZED UNDER: Cool stuff, NASA, Pretty pictures

Comments (34)

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  1. Charlie Young

    I’m just trying to figure out why the misconception of friction of air molecules causing the heat of re-entry has been perpetuated for so long. Has this fact been known since Mercury and before? All these years, I’ve been using an erroneous assumption. I never made the connection from physics that a gas heats up under compression.

  2. natasha

    thats really cool x

  3. GA

    That is a one hell of a once-in-a-lifetime shot!! Reminds me of the picture of Phoenix’s descent into Mars, taken by the Mars Reconnaissance Orbiter.

  4. Scott

    THAT’S the cause of global warming! Shuttle reentries adding heat to the atmosphere! :P

  5. Thanks for sharing Phil! With Charlie Young on his question, though…

    If friction — in the most basic sense, anyway — isn’t heating up the atmospheric gases around [insert descending high-speed object], then what is?

  6. I thought the glow also (mainly?) had to do with the energy transfer between the spacecraft and the atmosphere – basically the idea that the shuttle’s kinetic energy was being converted to heat as the craft slowed down. Maybe in some of his spare time (haha!) Phil should record a new BadAstronomer video on YouTube and give us all a lesson! ;)

  7. @1, probably because ram pressure is a lot less common-sense than friction.

    I remember it taking me a bit to get it. For most people’s purposes, “friction” is close enough. When you say “not friction, ram pressure” You’re exposing your science-brain and geeking out.

  8. SLC

    Relative to the ISS, here’s the latest comment from Prof. Bob Park.

    4. SPACE: A SPECTACULAR VIEW IS SAID TO BE AVAILABLE ON THE ISS.
    The so-called Tranquility Node has been successfully installed on the International Space Station. The 14-ton node will house Core life support systems, exercise equipment, robotic workstations and an unmatched view of Earth from a new viewing deck. Observations are made through the largest window ever sent into space. There are four more shuttle missions to the ISS planned for the next seven months before the shuttle fleet is retired. So far, unfortunately, there are no reports of anything new seen from the viewing deck. Earth, of course, is both complex and dynamic; there’s a lot to look at. Astronauts will therefore keep looking. If anything new is reported we will let you know at once. Whether this will attract additional paying space tourists is not clear.

  9. DrFlimmer

    Basically it’s a simple gas-law.

    pV=NkT. (1)

    (pressure*volume = number-of-particles*Boltzmann-constant*temperature)

    So, if you change the left-hand-side of the equation, the right-hand-side has to change as well. We can assume that N does not change by much (at least in a short enough time scale), so only the temperature can change.
    Here comes the shuttle crashing into the atmosphere with Mach25, which also justifies the assumption that N is constant (because the speed of sound (Mach1) is the velocity a change in the gas can be communicated to the other gas particles. If the disturbance is quicker than that (and in this case: a LOT bigger) then the particles have literally no time to go out of the way).
    First of all, what does happen when the shuttle enters the atmosphere? The volume is reduced and the pressure goes up. But this could still yield the same value, p*V could still be the same as before since one goes up and the other goes down. This would lead to an isothermal process, which means that the temperature stays constant.
    But this is not what happens here. Isothermal processes are relatively slow processes, since everything needs to adjust itself. But as I stated before, there is no time to adjust. The shuttle comes in with 25 times the speed of sound. There is no time.
    So, the process is not isothermal. In fact, it is what is called adiabatic. This means that the particles cannot transfer heat away to the surrounding medium and therefore change their temperature. But which way?
    For an adiabatic process the pressure and the volume are connected by this equation:

    p*(V^x)=const, (2)

    where x is called the adiabatic exponent and is defined by x=(f+2)/f, where f is the degree of freedom of the gas. In the case of an ideal gas (which we assume here) the degree of freedom is f=3, yielding x=5/3.
    Since Eq. (2) should always give the same constant result, the product is the same before the shuttle hits the atmosphere and when it has entered. Therefore we can rewrite Eq. (2) as

    p1* (V1)^x = p2* (V2)^x. (3)

    We can use the ideal gas-law Eq. (1) to substitute the pressure with

    p = NkT/V, (4)

    yielding

    N1*k*T1* (V1)^(x-1) = N2*k*T2* (V2)^(x-1). (5)

    Since N1=N2, this results in:

    T2 = T1* (V1/V2)^(x-1). (6)

    V2 < V1 means that the temperature goes up, just as we expected.
    And since Mach25 is a rather high speed, the gas beneath the shuttle becomes compressed quite a lot, and therefore the heat is rising a lot as well.

    Hopefully this mathematical explanation made this all a bit clearer. At least, it did for me ;)

  10. Dave Mosher: Charlie Young gives the answer in his post, namely, gas gets hotter when it is compressed. As Phil says, the atmosphere is “violently compressed” so that equals “really hot.”

  11. But the entire process can’t be adiabatic, for then as soon as the shuttle has passed and the gas got out of its way, it would bounce back to its original volume and the temperature would be back to what it was. Yet we are seeing a glorious, glowing tail. (Fortunately, since the picture would be rather boring otherwise.) So there must be all kinds of complicated heat transfer going on, including perhaps radiative heat transfer, since this gas is getting so awfully hot. Can anybody explain this part, in broad outline? (I expect the details to be horrendously complex.)

    PS. @natasha (#2), funny that you should say it’s cool when quite clearly, it is anything but.

  12. Calli Arcale

    As it’s doing that, it’s ramming the Earth’s air at something like Mach 25

    Minor correction: it’s going a lot slower by this point. Forgiving for a moment that “mach” is not entirely meaningful for the entire reentry (as it is a function of altitude as well as airspeed), orbital velocity for the Shuttle is about Mach 24. It loses a great deal of that velocity during the reentry process, of course, which is in fact the whole point of the reentry process. They bleed off a lot of speed in the S-turns. By the time the Columbia broke up over Texas, it had decelerated to about Mach 15. By the time a Shuttle aiming for KSC reaches the Caribbean, it has slowed down even more. The S-turns are pretty extreme — nose up 40 degrees, and banking up to 70 degrees.

  13. Rod Savard

    Fake. I can’t see any stars.

  14. @Rod: I don’t know if you’re serious or joking, so I’ll take you seriously: The picture is presumably taken from above. If there were stars in the picture, the photographer would have a David Bowman moment.

  15. Eric TF Bat

    So, Phil, give us the low-down on the “friction of re-entry” for the following objects:

    - a humanoid male, approximately six feet tall, with skintight blue suit and red cape;
    - a shuttle, the Galileo, registry number NCC-1701/7;
    - a blue box, spinning somewhat out of control, with a light on top and the label “POLICE BOX”.

    I’d love to know how much they’d typically heat up. You may need to guess at size and mass here and there, but if it helps I do know that all three have the ability to ignore gravity at will, so that may make it easier to fudge the figures…

  16. bluehigh

    Are you suggesting that friction is not the a priori cause of the gas compresion? It is hardly as though the shuttle is in a relative stationary position and limiting the volume for a specified density of molecules. Even though compressive effects generate photon radiation through kinetic energy transfer, the cause is friction.

    In fact the photon radiation occurs primarily from the formation of gas plasma by energy transfer from the shuttle surfaces (due to friction).

  17. Soichi Noguchi is always tweeting fantastic pictures from the ISS!

    Boomdeyada…

  18. markogts

    @ Failed protostar:

    energy (and moment) transfer can be accomplished through compression heating too: in front of the Shuttle there is a shock wave. It is in this shock wave that temperature increases abruptly. And so does pressure. But to have different pressures on two sides of the same area (the area of the shock wave) means somebody needs to apply some force, and – you guess it- this force is the braking force acting on the Shuttle. Multiply per time and you get the moment, multiply per distance and you get the energy. Af course, the air will not be the same after the Shuttle pass :-)

    @ Harald:

    adiabaticity is only taken in account in the thin layer of the shock wave. The difference between adiabatic and isotherm is mainly a matter of which time scale to choose. Take a one-hour time scale, and Shuttle reentry is isotherm, since both atmosphere and Shuttle will cool down in such a long time. Take the microsecond of the transit of the shockwave, and you have an adiabatic situation. Whatever comes in betweeen these two extremes will not be neither adiabatic nor isotherm. For example, we know that Shuttle tiles cool via radiative heat transfer. This implies non adiabaticity.

    @ bluehigh:

    Compression is due to the shockwaves.

  19. Pieter Kok

    I would still call that friction, because “friction” is not a single-mechanism force.

  20. DrFlimmer

    @ #14. Harald Hanche-Olsen

    I used a quite simplistic model, obviously. And I only wanted to show why the gas heats up due to compression and not friction.
    In fact, since the gas heats up it becomes a plasma, which changes everything and my simple model is not accurate any more. The plasma needs to cool, which means, the positive ions must recapture their lost electron(s). That needs a few moments of time, therefore you can see the glowing stream behind the shuttle. And that process is all but adiabatic ;)

    Btw: The production of plasma is the reason why we had the blackouts in communication with the Apollo capsules. Radio waves cannot penetrate a plasma (electrons can suck them up quite easily), so there was no communication possible with the space craft. It’s different with the shuttle. But I think this is due to the size and form of the shuttle and maybe that we have far more satellites up in the sky.

    @ #19. Pieter Kok

    Would you call the compression in a car engine also friction? Because it’s basically the same mechanism: Compression producing heat.
    There is of course some friction between the shuttle and the air, but the effect is minor.

  21. Jon Hanford

    #1. Charlie Young Says:
    February 22nd, 2010 at 1:53 pm

    I’m just trying to figure out why the misconception of friction of air molecules causing the heat of re-entry has been perpetuated for so long. Has this fact been known since Mercury and before? All these years, I’ve been using an erroneous assumption. I never made the connection from physics that a gas heats up under compression.

    Here’s a memorable example: http://www.phys.ncku.edu.tw/~astrolab/mirrors/apod_e/ap090302.html

  22. Jon Hanford

    Seems I’m stuck in moderator limbo. Try cut & pasting this address: (http:) //apod.nasa.gov/apod/ap090302.html

  23. Pieter Kok

    DrFlimmer, it all depends on what aspect you are interested in. In the case of the shuttle the dissipation mechanism is the ram pressure, which causes the shuttle to lose kinetic energy. I have no problem calling that friction. In the case of the engine, dissipation is not the main phenomenon you are interested in. Remember, friction is not a fundamental force.

  24. DrFlimmer

    @ Pieter Kok

    Obviously, it is all a matter of perspective, as usual ;) .
    I, for myself, have a specific idea what friction is (or should be): Something sliding over/through something else, normally a quite slow process. Ram pressure does not fit in my picture, but, again, that’s just me.

    Indeed, friction is not a fundamental force, and not very stringently defined. In fact, everything that dissipates heat or that causes loss of energy in a system is referred to as “friction”.
    In this sense you are right!

    So, yeah, maybe one could still call it friction what slows the shuttle. But if you can describe it more adequately, why not do it? And ram pressure describes what’s really going on, friction is a more general term, could be almost anything.

    Gee. You ARE right ;) . A shuttle is slowed down by friction, which is in this case ram pressure.
    :D

  25. Doug

    My friend the late Ron Parise was a Mission Specialist on a couple of shuttle missions. He had a picture at his house that someone sent him of a glowing shuttle reentry trail over Hawaii. He was aboard that mission, so he referred to the picture as: “Me, as a bolide.”

  26. Jim

    Any idea what the scale and view angle are in the photo? Presumably the shuttle is heading eastward. Was the ISS west or east of the shuttle?

  27. Very helpful words, DrFlimmer. And at #24.:

    “In fact, everything that dissipates heat or that causes loss of energy in a system is referred to as “friction”.”

    THAT is what I was getting at, and confused by in the post. I personally take the “big picture” look at things… whether that’s textbook-correct or not, I’ll leave to the physics pros.

    Perhaps some conditional wording would have cleared things up:

    “This is what causes the Orbiter (as well as incoming meteors) to glow, not friction — in a highly technical sense, anyway.”

  28. Jim

    What causes it to glow is the friction from all the arguments.

  29. Matt

    It would be the Gulf of Mexico, not the Caribbean Sea.

  30. Sfwan

    “Friction” is the production of phonon waves within 2 sliding surface. This is because: when 2 sliding surface were to continuously re-connecting and dis-connecting due to local electrostatic charge, it causes molecular vibration inside those 2 material, which is called “phonon”. –Phonon which had similar frequency to infrared radiation will create heat… (hence… the common dogma: ” friction cause heat”). (the production of phonon also ‘suck-up’ the energy of the sliding material, hence … the common dogma: “friction slow things down”)

    I agree @DrFlimmer: ” friction has minor effect in shuttle re-entry”. Thanks for mentioning it.

  31. A similar – even better perhaps – image was taken from the International Space Station on the very final Space Shuttle mission ever (STS-135, Atlantis) in July 2011.

    Click on my name here to see it or see ‘The fiery descent of Atlantis… seen from space!’ posted by the BA on the 22nd July 2011 at 6:00 AM.

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