Low weight gps

[FZeroWing]

Hello everyone,

I am currently participating in a competition called the N-Prize where a group must put into orbit (99.99 Km) around the Earth a satellite with a mass of between 9.99 and 19.99 grams, and to prove that it has completed at least 9 orbits all under the price of £999.99.

I would like to request assistance with attaining a GPS that weighs 19.99 grams or less, that can be tracked at a maximum altitude of 100Km or more if possible. I did search around and found this
https://www.northstarst.com/CAT/PDF_Upload/20GramStd.pdf
However it's much to expensive. I did look into a previous post about a GPS unit, and read about the Big Red Bee GPS I was wondering if that would be a viable solution to the problem.

Any assistance would be appreciated

Thank you

 

[mikec]

Any assistance would be appreciated

I think you want to use a simple radio beacon and not GPS. No commercial GPS will lock up in earth orbit due to COCOM limits.

The Beeline beacon would likely work fine for this application.

 

[FZeroWing]

hey mikec

thanks for the quick reply, I took a look at the beeline beacon as you suggested I was wondering if it's possible to fit it with a solar cell replacing the battery that the beacon has.

 

[mikec]

hey mikec

thanks for the quick reply, I took a look at the beeline beacon as you suggested I was wondering if it's possible to fit it with a solar cell replacing the battery that the beacon has.

If you had a solar cell with the right voltage and current output, though it would be safer to just stick with a battery to avoid having to worry about orientation and shadowing. I'm sure there would be ways to reduce the mass of the beacon as a custom job.

Do you really think you know how to build a rocket that can put 10 grams into earth orbit?

 

[MarkH]

If you had a solar cell with the right voltage and current output, though it would be safer to just stick with a battery to avoid having to worry about orientation and shadowing. I'm sure there would be ways to reduce the mass of the beacon as a custom job.

Do you really think you know how to build a rocket that can put 10 grams into earth orbit?

Rockoon?:eyeroll:

 

[Lentamental]

Rockoon?:eyeroll:

Now, now, lets not bring that up here... But it is a good question. Does your group have a page we can check out to see your exciting work?

 

[FZeroWing]

We are actually planning on a rockoon launch, mainly since we can keep within the budget range with it.

Unfortunately we don't have a website our main methods of communication is a google group and meeting in person. We plan on making a website soon though.
However I am willing to divulge any and all the information and design plans we are currently working with , if that is fine with you.

 

[mikec]

We are actually planning on a rockoon launch, mainly since we can keep within the budget range with it.

Some questions:

1) Are you making your own motors? If so, what kind?

2) Are you going to have any onboard guidance?

3) How do you plan to get an FAA waiver to fly this?

4) What kind of rocketry experience do you have?

 

[FZeroWing]

Some questions:

1) Are you making your own motors? If so, what kind?

2) Are you going to have any onboard guidance?

3) How do you plan to get an FAA waiver to fly this?

4) What kind of rocketry experience do you have?

1) Yes, we are planning on working with a hybrid motor

2) Currently contemplating on either using a system similar to the V2 rocket or use ArduIMU . However, we are probably going to end up using ArduIMU since it's basically got everything in it already.

3) We are in process of applying for an experimental launch permit, which we hopefully get. However even if we do not get the permit it would still be an achievement of building a rocket of this scale for us.

4) Built and flew many model rockets all a bit the largest motor I ever used was a D motor, also I am currently studying Aerospace Engineering at University.

I hope I have answered your questions properly.

 

[bobkrech]

Hello everyone,

I am currently participating in a competition called the N-Prize where a group must put into orbit (99.99 Km) around the Earth a satellite with a mass of between 9.99 and 19.99 grams, and to prove that it has completed at least 9 orbits all under the price of £999.99.

I would like to request assistance with attaining a GPS that weighs 19.99 grams or less, that can be tracked at a maximum altitude of 100Km or more if possible. I did search around and found this
https://www.northstarst.com/CAT/PDF_Upload/20GramStd.pdf
However it's much to expensive. I did look into a previous post about a GPS unit, and read about the Big Red Bee GPS I was wondering if that would be a viable solution to the problem.

Any assistance would be appreciated

Thank you

If you're worrying about the cost of GPS transmitter, you don't have enough money to play.

Bob

 

[rdbones]

If you're worrying about the cost of GPS transmitter, you don't have enough money to play.

Bob

Bob - Remember he said

I am currently participating in a competition called the N-Prize where a group must put into orbit (99.99 Km) around the Earth a satellite with a mass of between 9.99 and 19.99 grams, and to prove that it has completed at least 9 orbits all under the price of £999.99.

 

[mikec]

1) Yes, we are planning on working with a hybrid motor

Have you ever built a hybrid motor before? How many stages, mass ratio, etc?
Is this a university project? Which one?

 

[sylvie369]

If you're worrying about the cost of GPS transmitter, you don't have enough money to play.

Bob

Remember that they only get to work with £999.99 (something like $1500). It's possible that he means that the GPS would take too much of that limit, not that he doesn't have the money to pay for it.

I took a look at this challenge because it didn't look right, or more accurately, it didn't look possible, but yup, that's the contest: launch a rocket into orbit for about $1500, and keep the satellite's weight to between 10 and 20 grams (for reference, an Estes Alpha weighs 23 grams empty, and so would be too heavy to qualify as the satellite). Complete at least 9 orbits.

I don't see how you could possibly have the electronics in orbit to verify the orbits as required and yet keep the weight below 20 grams - it seems to me that you'd have to have just a passive reflective object and somehow track it from the ground. Maybe, just maybe a coin-cell powered radio transmitter could do it, but a standard CR 2032 cell weighs about 3 grams, so you wouldn't have much else to work with. I certainly can't see also having a GPS and antenna, plus power for that, added to the transmitter and its power supply.

 

[mikec]

Maybe, just maybe a coin-cell powered radio transmitter could do it, but a standard CR 2032 cell weighs about 3 grams...

Small lipos or supercaps could be lighter, but you're right, any active electronics don't leave you with much to work with. Note that by the rules if you jettison the transmitter from a larger object and call the transmitter the satellite, that's OK.

Maybe solar cells do make some sense, though you'll only be transmitting in daylight. Designing a single PCB with a CC1050 radio chip and a solar cell with some power conditioning would be a fun project, and I bet doable for under 20g.

Building the payload, which challenging, is probably at least 1000x easier than building the rocket.

 

[Adrian A]

At least they're honest about it:

From the site:

What is the N-Prize?

The N-Prize is a challenge to launch an impossibly small satellite into orbit on a ludicrously small budget, for a pitifully small cash prize.

Making a transmitter that could be heard with a handheld YAGI intermittently for 15 hours, from orbit, could be done for about 10-15 grams, with battery. It wouldn't include GPS, bit it could still prove the achievement of orbit by the timing of the signals and the Doppler shift.

Its recurring cost as an expendable part of the flight would be about $20. You'd have to enlist the free help of HAMs around the world to listen for it, but I could see that happening.

The rest of the rocket is the silly part.

 

[mikec]

The rest of the rocket is the silly part.

While I tend to agree, some people who have some degree of demonstrated track record (like SS2S) are talking about making attempts. I haven't done the math to see what the numbers look like for ground-launched solids, and there's no need to rehash the rockoon debate.

https://www.microlaunchers.com/7816/L3/sa09/sa09.html has a plan using a 3-stage liquid (LOX/propane) with a GLOW of 60 kg. Not sure if this is credible.

 

[bobkrech]

Bob - Remember he said

I know exactly what he said.

 

[Adrian A]

While I tend to agree, some people who have some degree of demonstrated track record (like SS2S) are talking about making attempts. I haven't done the math to see what the numbers look like for ground-launched solids, and there's no need to rehash the rockoon debate.

https://www.microlaunchers.com/7816/L3/sa09/sa09.html has a plan using a 3-stage liquid (LOX/propane) with a GLOW of 60 kg. Not sure if this is credible.

My greatest skepticism applies to the $1500 recurring cost. That's supposed to include the cost of everything that's not recovered.

To give an idea of the difficulty, consider an N5800 as a reference. It has the highest impulse/mass ratio of any commercial motor that I know of. If you were to take the motor by itself, raise it out of the atmosphere entirely, and magically guide it in one direction during the burn with a massless system, it could provide about 2 km/second of delta-V, if I did my math right. Orbital velocity is about 9.3 km/second. So you would need many stages, maybe 4 to 7, even with a rockoon launch and making you own custom motors that have a better mass impulse/kg than the N5800. Each stage should be about 4x the mass of the next stage for best efficiency, so you're talking about very small rockets at one end, and very large rockets for the initial booster. The propellant alone would probably run around $1500, and you would have to recover most of the stages in order to get under the cap.

A G80 is also a relatively efficient engine, at a smaller scale. It would provide 1.5 Km/second if you were to fire it by itself. It could be kind of an interesting exercise to see how many stages of commercial motors it would take to add up to 9.3 km/second.

I just whipped up a quick spreadsheet to get an idea of the feasibility, and started with an Apogee D10 pushing an extra 20 grams. Then used a G80 to push that plus an extra 30 grams. Then used a I350 to push that plus 120 grams. I've used up all my disposable stages and I've only gotten to 2.2 km/second out of the 9.3 needed. And that's assuming no drag or gravity losses. After this, you would need to start recovering the stages or else you'll run out of money. Someone can keep adding stages if they want, to see what it takes to get up to 9.3 km/sec. And then figure out what big stage will get that whole stack up out of the atmosphere. All for under $1500.

View attachment Rocket Equation staging calcs.xlsx

 

[bobkrech]

Beginner's Guide to Rockets is an excellent series of NASA tutorials on rockets. Guided Tours is a good starting point.

If you work your way through them, you will see that the N-Prize contest is a pipe dream thought up by some folks who encountered aliens......

MIB is a movie about the government agency with the real solution.....

Bob​

 

[Adrian A]

Beginner's Guide to Rockets is an excellent series of NASA tutorials on rockets. Guided Tours is a good starting point.

If you work your way through them, you will see that the N-Prize contest is a pipe dream thought up by some folks who encountered aliens......

MIB is a movie about the government agency with the real solution.....

Bob​

Thanks, Bob. There are some useful calculators in there, like this one:

https://exploration.grc.nasa.gov/education/rocket/atmosi.html

which makes it easy to compare, for example, the stagnation temperature for rockets I've flown to ones that I'm planning. Good stuff.

 

[edwinshap1]

i'll leave all the non GPS stuff out of this.

It seems that he lives in the UK, so I'm honestly not sure about the laws regarding GPS at high alt/velocity, but I know that in the US, it is possible to buy an unlocked one after an expensive application and an expensive payment to the GPS manufacturer. However, I don't know of a GPS unit weighing under 20 grams that can have that done to it.

 

[cjl]

As has already been mentioned by Adrian and Bob, this doesn't seem possible. Getting to orbit is much, much more difficult than getting to space, and above all else, requires an enormous delta v. Delta v is really only dependent on mass ratio and specific impulse, so somehow, you would need a very high Isp and good mass ratio in a tiny rocket. The only even slightly doable method I can think of involves 2 stages, custom built, using all liquid fuel, but that completely blows the budget out of the water. A hybrid (as stated above) is almost sure to not work, due to the poor mass fraction and mediocre Isp.

In addition to the high delta v required, getting to orbit requires some kind of active guidance. Since most of the acceleration occurs above the atmosphere, aerodynamic guidance is out, as is aerodynamic stability. Passive spin stabilization is also out, since the rocket must turn during ascent to accelerate tangentially to the earth's surface to attain orbit. An IMU and servo system capable of guiding the rocket alone would likely cost more than the allowable recurring cost for this entire system.

Basically, as far as I can tell, this is an impossible challenge.

(Also, you'll definitely need to get it higher than 99.99 km - at that altitude, atmospheric drag would cause the orbit to decay before it had completed the requisite 9 orbits).