Silicon Investor (SI) -- The First Internet Community

STOCKTALK

We've detected that you're using an ad content blocking browser plug-in or feature. Ads provide a critical source of revenue to the continued operation of Silicon Investor. We ask that you disable ad blocking while on Silicon Investor in the best interests of our community. If you are not using an ad blocker but are still receiving this message, make sure your browser's tracking protection is set to the 'standard' level.

Microcap & Penny Stocks : Globalstar Telecommunications Limited GSAT -- Ignore unavailable to you. Want to Upgrade?

To: CommSatMan who wrote (4008)	4/21/1999 8:56:00 PM
From: Mr. Adrenaline	Read Replies (2) \| Respond to of 29987

I really debated with myself as to whether or not I should respond, because I don't see a response contributing to the knowledge pool that SI readers are seeking. But, I couldn't help myself -- my experience includes lifetime fuel budgets that can be almost 10 times what you are quoting. 5 kg of fuel for a 10 year life will preclude the satellite from being larger than about 100 kg with a more likely figure of about 30 to 50 kg. That may well be your experience, but not too many satellite fit that category. 100 kg is usually the limit for "small" satellites, and 30 to 50 kg is definitely in the "micro" satellite class. To reach that conclusion, all I have to do is make an assumption about Isp. Typical chemical thrusters for orbit keeping are in the 150 to 250 second range for specific impulse -- let's use 200 seconds. Isp = MsDv/Mpg where Isp is the specific impulse Ms is the mass of the satellite I'm trying to find Dv is the delta-V Mp is the mass of the propellant -- 5 kg for ths case and g is gravity at 9.8 m/s^2, which I'll call 10 because I'm lazy.. If I assume the mass of the satellite is much larger than that of the propellant, then the change in the mass of the satellite doesn't change too much as propellant is consumed. That makes the math easy-peasy. You quoted a range of 15 to 75 m/s of delta-v per year, and I think that's a good figure. Let's low ball it, and call it 10 to keep the math easy. That makes 100 m/s for the mission. So now I'm left with 200 = Ms100/510 Solving for Ms yields 100 kg. That's a pretty small satellite. If I use a more reasonable number for delta-v, say 25 m/s, satellite mass drops to 40 kg. I hope you don't think I'm picking on you -- I'm not. But your quoting of 5 kg of propellant for entire mission is a concept so foreign to me that I marvel that it could be fact. By your posts I'm guessing that your expertise is in payloads...? Regards, Mr A