Discussion Developing my first satellite

[RisingFury]

-Small (1.3 m^3), of course

Assuming UCGO box dimensions, 1.3 m * 1.3 m * 1.3 m does not equal a volume of 1.3 m^3. It's just under 2.2 m^3

Admittedly it is harder to grasp using tutorials on the internet than it is to have a programming course shove the paradigms down your throat,

In my experience, finding a tutorial the suits you and learning programming from your comfortable armchair is much more effective than learning it at a university course. Courses are usually crush-courses, not tutorials.

 

[Pipcard]

Thank you, but enough about C++. That's for later. Let's talk about antennae and propellants for a small satellite.

 

[RisingFury]

Thank you, but enough about C++. That's for later. Let's talk about antennae and propellants for a small satellite.

Can't you at least open up some other websites, instead of just asking everyone to give you instructions on what to do? Do your damn research, man.

 

[Pipcard]

Can't you at least open up some other websites, instead of just asking everyone to give you instructions on what to do? Do your damn research, man.

The thrusters could be very simple, even as simple as compressed nitrogen.

How does he know that compressed nitrogen can be a good propellant for small satellites? Are there any other propellants that are good for the attitude control of small satellites (not big satellites only) and what are their parameters? What is recommended for a 2.2 m^3 satellite? A definitive list is hard to search for.

 

[garyw]

How does he know that compressed nitrogen can be a good propellant for small satellites?

It doesn't matter. All you need is to be able to squirt something out of the satellite so it moves in the opposite direction. Your reaction mass can be anything. Ideally you want something intert (nitrogen) or reactive such as the prop used in the RCS system of the shuttle and no I'm not telling you want it is - go do some research and find out.

You can even use water - it really doesn't matter - what DOES matter is how much thrust you get for a given expenditure of fuel.

Over to you.

 

[RisingFury]

How does he know that compressed nitrogen can be a good propellant for small satellites? Are there any other propellants that are good for small satellites (not big satellites only) and what are their parameters? A definitive list is hard to search for.

So find multiple sources, compare the pros and cons as they fit into your sat and make a decision.

Do you ask your mom to pick out the food you eat, because she knows best?

 

[Urwumpe]

also, there are many different kinds of thrusters that you can use for attitude control, and also there are forms of attitude control that don't use any thruster - for example using earths magnetic field works great for small satellites in low orbit.

 

[garyw]

for example using earths magnetic field works great for small satellites in low orbit.

I've not heard of that one only of Reaction wheels and gravity gradient booms

 

[Zatnikitelman]

There's also solar sails out on booms as well.

 

[Urwumpe]

I've not heard of that one only of Reaction wheels and gravity gradient booms

It was already used for at least two european scientific satellites, I just look through my university papers about the names of them.

http://www.raumfahrt.fh-aachen.de/c...highly inclined circular Low Earth Orbits.pdf

 

[RisingFury]

I've not heard of that one only of Reaction wheels and gravity gradient booms

It does work and you can use the Earth's magnetic field to help you propel the satellites as well, but it works best where the magnetic field density is high - over the magnetic poles, so it's only useful for orbits that are highly inclined and quite low.

 

[Pipcard]

Is it easy to simulate reaction wheels? Maybe they're the way to go.

(So I did some digging around and found the ISP of compressed nitrogen to be about 68 s.
The key words were "cold gas thruster". Now: the density of compressed nitrogen?)

 

[garyw]

Now: the density of compressed nitrogen?

how about a please or maybe a thank you for the help so far?

And what level of compression are we talking about?

 

[Pipcard]

how about a please or maybe a thank you for the help so far?

And what level of compression are we talking about?

Thank you all for the help. The compression level found in compressed nitrogen gas engines.

I don't think reaction wheels work like RCS, so they can't be properly simulated without me having to code (let's not get into that right now).

Cold gas systems:
There is a chart of engines with nitrogen propellant. What exactly is meant by "inlet pressure"? Is it the pressure that the nitrogen is stored at?

 

[Urwumpe]

Please learn about ideal gas law.

And the compression used there is variable. inlet pressure is the pressure at which it enters the engine assembly, past valves, tanks and regulators.

 

[garyw]

The compression level found in compressed nitrogen gas engines.

Which is varible depending on what you want to use.

I don't think reaction wheels work like RCS, so they can't be properly simulated without me having to code (let's not get into that right now).

Reaction wheels turn a satellite to a given attitude. Don't you want RCS to do that? If so, how can you say 'reaction wheels don't work like RCS'

Cold gas systems:
There is a chart of engines with nitrogen propellant. What exactly is meant by "inlet pressure"? Is it the pressure that the nitrogen is stored at?

Nope. It's the pressure required to transfer it from the tank to the thruster, inlet basically meaning 'letting it in' to the thruster.

 

[Pipcard]

Please learn about ideal gas law.

And the compression used there is variable.

Okay. Is there an average pressure?

So when they say "cold gas", do they mean that it's stored at temperatures near absolute zero?

 

[Urwumpe]

So when they say "cold gas", do they mean that it's stored at temperatures near absolute zero?

No, it means it is not heated by the thrusters by any means, may it be chemical, nuclear or electrical. It is simply blown through a convergent-divergent nozzle at high pressure.

There are standard formulas to describe the conditions in a combustion chamber, that also apply to cold gas thrusters, and for describing nozzle performance, but I won't tell you now. First of all, because I see that you are not ready set for such details, you are at square one still. second, I feel you are a bit impolite and should not get more than just hints how to learn the things yourself or how to understand the things you have already found, so you can learn them.

 

[Pipcard]

No, it means it is not heated by the thrusters by any means, may it be chemical, nuclear or electrical. It is simply blown through a convergent-divergent nozzle at high pressure.

There are standard formulas to describe the conditions in a combustion chamber, that also apply to cold gas thrusters, and for describing nozzle performance, but I won't tell you now. First of all, because I see that you are not ready set for such details, you are at square one still. second, I feel you are a bit impolite and should not get more than just hints how to learn the things yourself or how to understand the things you have already found, so you can learn them.

Okay, forget the thrusters. This satellite will have no attitude control system at all. I'm still at high school Chemistry (Physics is next year).

Also, you are calling me impolite?

Can't you at least open up some other websites, instead of just asking everyone to give you instructions on what to do? Do your damn research, man.

 

[Urwumpe]

Okay, forget the thrusters. This satellite will have no attitude control system at all. I'm still at high school Chemistry (Physics is next year).

If you wait until somebody teaches you everything you need to know for a task, you will NEVER get anything done. I can't do the thinking for you, nobody here can. I can point you to teaching material, but you would have to learn it.

And forget school. My teachers had been still busy teaching me BASIC, when I wrote a program on an Atari ST, that was capable of disassembling windows executables (OK, it was written in GFA Basic back then, because I still had no C compiler for the Atari ST).

Do you want to design your own cubesat and get it into Orbiter?
[ ] Yes
[ ] No
[ ] Maybe