Formula to calculate air loss?

Thread view:

Enable EMail Alerts

Start New Thread

Thread rating:

JamesStep - 24 Sep 2003 01:59 GMT

Is there a formula or rule-of-thumb for making a rough
estimate of the rate of air loss in a space craft for a
given size air leak?

- James
++++++++++++++++++++++++++++++++++++++++++++++++
Remove "NOSPAM" from my address when sending me e-mail.
++++++++++++++++++++++++++++++++++++++++++++++++
-

Reply to this Message

Henry Spencer - 25 Sep 2003 22:40 GMT

>Is there a formula or rule-of-thumb for making a rough
>estimate of the rate of air loss in a space craft for a
>given size air leak?

Hmm, a crude first approximation would be to assume that the air is moving
through the hole at the speed of sound ("choked flow"), with its density
and temperature unchanged. So if it's normal air at room temperature
(speed of sound about 350m/s), you lose about 35 liters per second through
a 1cm^2 hole.

Signature

MOST launched 1015 EDT 30 June, separated 1046, | Henry Spencer
first ground-station pass 1651, all nominal! | henry@spsystems.net

Reply to this Message

Bill Bogen - 26 Sep 2003 19:16 GMT

> >Is there a formula or rule-of-thumb for making a rough
> >estimate of the rate of air loss in a space craft for a
[quoted text clipped - 5 lines]
> (speed of sound about 350m/s), you lose about 35 liters per second through
> a 1cm^2 hole.

Yep. The flow, Q (in liters/sec) ~ 9.1 * sqrt(Pressure (in psi)).
So if the space craft has an air pressure of 7 psi (about 1/2
atmosphere), you'd lose about 24 liters per second.

Reply to this Message

Space Forum / Space Flight / September 2003

Formula to calculate air loss?