7
$\begingroup$

The ISS orbits in the thermosphere and needs periodic re-boosts because of air-drag. At the other extreme, the slowest(?) fixed-wing aircraft are f1d planes made out of 2 grams of balsa wood, microfilm, and rubber bands.

How would an F1D plane, built for low-speed dense air, react to the tenuous but hypersonic wind outside the ISS? Would the plane be visibly buffeted and slowed down?

$\endgroup$

1 Answer 1

6
$\begingroup$

So, I just put both Objects in a numerical Propagator (HPOP):

(EGM2008 1x1, NRLMSISE 2000, No tides, No third bodies, No SRP, No radiation pressure, LEO, Cd=2.2, F10.7 = 150 (fixed))

ISS:

  • Mass 450 000 kg
  • Area 10 000 m²
  • Area/Mass Ratio 0.022 m²/kg

F1D:

  • Mass 0.002 kg
  • Area 0.5 m²,
  • Area/Mass Ratio 250 m²/kg

Result:

  • After 10 sec 22m range between both objects
  • After just 1 minute, both objects are 811 m apart
  • 3216 m after 2 minutes...

Answer:

YES! You can see the plane visibly buffeted and slowed down.

$\endgroup$
6
  • 4
    $\begingroup$ Given how hypersonic gases work at such low pressure suspect 'no' to the buffeted part of the question, this will be pure 'atoms hit and either stick or bounce' rather than having any sort of 'flow'. Maths behind en.wikipedia.org/wiki/K%C3%A1rm%C3%A1n_line is also relevant. $\endgroup$ Commented Jan 18, 2023 at 10:10
  • 4
    $\begingroup$ From what I remember low-density objects released on ISS EVAs don't experience that kind of acceleration in real life. This video shows an insulation blanket (trunnion cover) inadvertently released on STS-88 and it just kind of hangs there. youtu.be/IXqw6NpCwIg?t=76 $\endgroup$ Commented Jan 18, 2023 at 13:56
  • 3
    $\begingroup$ It seems the plane's wing area is closer to 0.1 m² than 0.5 m². In addition, it would matter which way around the plane is - due to non-aerodynamic low pressure environment, facing the flow would cause almost no drag. $\endgroup$
    – jpa
    Commented Jan 18, 2023 at 16:59
  • 1
    $\begingroup$ @Organic Marble: The f1d uses microfilm that is only 0.5um thick and shows soap-bubble colors. A consumer "space blanket" is 0.5mm thick (1000 times thicker), presumably the insulator is similar. The OP also overestimated area by ~5 fold. $\endgroup$ Commented Jan 18, 2023 at 19:32
  • 5
    $\begingroup$ I cannot comment on the computations, but this answer sounds very implausible to me. It would imply that if an astronaut on an EVA drops a small piece of cloth, it would immediately depart and be out of sight within seconds. It would also imply that there should be buffeting on any loose strap or piece of cloth. None of which I have every heard of (I wouldn't mind to be corrected about it). $\endgroup$ Commented Jan 18, 2023 at 20:10

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.