Personal Satellites?
teganburns
Posts: 134
I have pondered the idea of a personal satellite and i feel like I'm not the only one on the forum who has also.
Have done a little research in the past and it doesn't seem like there would be too much of a legal problem (as long as it won't re-enter the atmosphere)
I'm not really clear on how far or difficult it would to get 1,200 miles up. (Could use a weather balloon or two to get you part way?)
and then keeping the orbit up as so not to burn up in the atmosphere.
maybe start a mini space station lol :P
Have done a little research in the past and it doesn't seem like there would be too much of a legal problem (as long as it won't re-enter the atmosphere)
I'm not really clear on how far or difficult it would to get 1,200 miles up. (Could use a weather balloon or two to get you part way?)
and then keeping the orbit up as so not to burn up in the atmosphere.
maybe start a mini space station lol :P
Comments
I am not sure about getting there, and I tend to lean towards the idea that what goes up must come down.
About the lowest Earth orbit is 150Km before you get into trouble with the atmosphere.
If you want a geostationary orbit you want to be at 35768Km.
Let's see what energy we require to get a 1Kg satellite up to 150Km.
E = mgh = 1 * 9.81 * 150000 = 1471500 joules.
That's about the energy you get from burning 0.01 US gallons of gasoline. Seems quite doable.
But as Loopy says what goes up must come down, unless you have the required orbital speed. Which is about 7900 meters per second or about 28000 km/second or 17600 miles per hour !
http://www.stuegli.com/phyzx/calculators/calc-orbitvel.htm
What energy do we need to get that speed?
Kinetic energy = (m * v * v) / 2 or about 31205000 joules.
Hey that's only 0.23 gallons of gas. Quite doable! Why is NASA and co building such huge rockets.
Can anyone spot the flaw in the argument so far?
I like the idea of a formation of tiny microsatellites all working together. Maybe as a space telescope or something. Entirely doable [edit - oops, I mean completely impossible] with propeller type technology - indeed such microsatellites would need to be very low powered and yet have enough smarts to collect data and relay it. Take it to another level and have a little fuel tanker that shuttles between the microsatellites to refuel their attitude thrusters.
So don't go adding to the mess unless you are going to clean up after yourself.
Don't forget. It's no use basing your satellite on a Propeller as everyone knows propellers don't work in space.
http://en.wikipedia.org/wiki/KickSat
For 300 odd dollars you could have been in the club of amateur satellite launchers:
http://www.kickstarter.com/projects/zacinaction/kicksat-your-personal-spacecraft-in-space
So long as you know how to use "The Force" to lift things, you're spot on.
I'm going to email a few major companies and who ever else i can find to see if i can get an price tag on doing this myself.
Gasoline can't move you on its own. You need to put it into a a machine which uses it as fuel to lift the payload. Since that machine will have mass it will require fuel to lift it into orbit as well. Most of that fuel will also need to achieve high velocity, so it will need fuel to lift it off the ground. Some of that fuel will also need additional fuel to lift it off the ground. So things quickly get out of hand.
The above also neglects the efficiency of a rocket which decreases as its velocity increases. So you'll use more fuel at the end of your boost phase per unit of weight.
http://lawreview.richmond.edu/exploring-the-commercial-space-launch-act/
In particular section IV, which describes the US regulatory environment. I'm pretty sure I've seen elsewhere that if you are a US citizen this applies to you even if you conduct your launch from another country or international waters. Much of the verbiage has to do with liability, which can fall back to your country even if you're not operating from within your own borders.
Oh and I dont know the specific gravity of petrol is but anyway
I gallon = 10lbs = 4.54kg (for water)
0.23 gallons = .23 x 4.54 = 1.045kg
So if the satellite was ONLY fuel - no motor - no body - no control systems....
I guess we need something with a higher calorific value than petrol.
(are my sums right???)
Dave
I believe it is the other way around.
http://en.wikipedia.org/wiki/Space_gun
http://www.space.com/20805-space-debris-european-conference.html
The effect I'm thinking about is that as a rocket's velocity approaches the exhaust velocity from the nozzle it becomes hard for the rocket to accelerate. Once it is traveling faster than the exhaust velocity fuel consumption increases dramatically. This is a problem for rockets that use chemical energy because they are constrained by how hot they can get the gases, which limits exhaust velocity.
For example the use of nuclear energy allows much higher temperatures than chemical energy. So a fusion or fission rocket can accelerate to higher velocities before this effect kicks in. Ion engines accelerate particles to such high velocities that they're efficient to extremely high velocities.
Given that we are launching from the ground we have air resistance to overcome. That will go up with the square of our speed. So as we accelerate we lose more energy into heat and our efficiency drops.
That is until the air thins into a vacuum as we reach into space.
Heck, this is complicated stuff...
Indeed, Wikipedia has a good article on Specific Impulse http://en.wikipedia.org/wiki/Specific_impulse and this diagram shows the relation between Mach number and propulsion performance:
Not being a rocket scientist I could be murdering this concept. But it isn't that the engine's efficiency changes, but the amount of propellant required to increase velocity changes as velocity increases. If you view efficiency as the amount of propellant consumed per unit of velocity increase, then efficiency does drop as velocity increases.
Maybe this is related (or maybe not (or maybe I'm just out of my mind.)), but I seem to recall looking at film of the Space Shuttle rising at high altitude and seeing that its exhaust gases were actually ascending at high velocity with respect to earth. The relative motions of the Shuttle and its exhaust gases were in opposite directions, of course, but the velocity of the exhaust gases with respect to earth was a different matter.
Yes, that is exactly the problem. An ideal rocket accelerates its reaction mass to a velocity greater than its own, this results in the gases being at rest or traveling backwards with respect to Earth. The fact that the reaction mass is traveling forward and upward means the rocket's efficiency is low.
The thing about the rocket approcahing the velocity of its exhaust and therfore becoming less efficient is not correct. If the mass of the rocket did not change due to fuel being burned it would continue accelerating at a constant rate for a constant power setting. The reality is that the mass decreases so a constant power setting yields increased acceleration - or a constant acceleration with decreasing power ie., increased effieciency.
Gaining efficiency due to loss of mass is true. However, a rocket still has a large amount of propellant during the phase in which it is traveling faster than its exhaust. Here's a quote from the Energy Efficiency section from the linked Wikipedia article:
Update: It's the kinetic energy of the reaction mass relative to Earth and not the rocket that's important. That's energy that would have been available to accelerate the rocket to orbital velocity with respect to the Earth. That's why higher reaction mass velocities are desirable as the rocket travels faster.
The exponentially increasing fuel requirements as mach number increases occurs during the early boost phase, not when the craft is actually going fast than its exhaust velocity. The problem is lifting the fuel you'll use later in the flight which is dead weight earlier in the flight. If you fired the rocket out of a gun faster than its exhaust velocity you wouldn't see that cost later in the flight because you skipped the early part of the flight.
Also, any rocket engine is going to be more efficient in space than in atmosphere. The atmospheric pressure reduces the amount which the exhaust gasses can expand. Until sufficient altitude is reached, not all of the nozzle is being utilized by the expanding gasses so maximum thrust is not realized until the nozzle design altitude is reached. Additionally, the atmosphere slows down the exhaust as it has to push though it, which reduces efficiency.
Also, the reason nuclear thermal or laser heat exchanger engines are good isn't because of operating temperature. (chemical engines mostly run hotter) They're good because they can use pure hydrogen as reaction mass. For a given exhaust temperature, a pure hydrogen exhaust at least doubles the specific impulse versus a pure water exhaust. (don't quote me on this, I haven't run the math, the gist is right anyway)
Lawson
http://humanoidolabs.blogspot.tw/2012/12/temporary-satellite-tsat.html