[amsat-bb] BY70-1

[Howie DeFelice]

Very interesting Phil, it seems to make sense that this calculation could be used in reverse to calculate the energy needed raise the perigee height of a GTO orbit. Assuming a flight to GTO was available to a 1U or 3U cubesat, if the perigee is not raised the satellite will not stay in orbit very long, if I understand it correctly. Given the limited size of the spacecraft and the prohibition on volatile propellants this poses a difficult challenge. It would be interesting to determine if enough thrust can be generated by electrical thrusters to accomplish this ?


- Howie AB2S

________________________________
From: AMSAT-BB <amsat-bb-bounces at amsat.org> on behalf of Phil Karn <karn at ka9q.net>
Sent: Friday, February 24, 2017 12:53 AM
To: amsat-bb at amsat.org
Subject: Re: [amsat-bb] BY70-1

Here's a first calculation of the power dissipation in BY70-1 during its
decay.

The highest will be for the period between the last two sets before
decay, which have epochs:

Fri Feb 17 17:37:01.530336 2017 UTC
Fri Feb 17 22:00:25.286112 2017 UTC

i.e., roughly 4.5 hours apart. The specific orbital energy at the first
epoch was -3.044e7 J/kg and -3.054e7 J/kg at the second.

The energy decreased by 100 kJ/kg during this time, so over 4.5 hours
that's an average of about 6.2 watts per kilogram. Multiply that by the
(unknown?) mass of the spacecraft to determine the actual drag power
dissipation in watts.

Depending on how much of that heat was conducted into the spacecraft, I
suppose it would have shown up as a temperature increase in telemetry
but not necessarily enough to cause the electronics to fail.

Decay was about 2.25 hours after the last eleset, and obviously the
power dissipation rose quite sharply toward the end of that interval...

Phil
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