Electric Solid Propellants

[sgt_flyer]

5 minutes ago, RainDreamer said:

Soo...basically C4? Just in a more productive form for space flight?

err C-4 explosion is triggered by both heat and shockwave at the same time - you basicaly need a detonator to trigger C-4 explosion .

this electric solid propellant simply start to combust when electric current pass through it - and the combustion stops when you stop applying current to the stuff (and if there's still fuel left, it can still reignite afterwards when you reapply current)  . at this point, it's just a matter of getting the resulting gases from the combustion through a nozzle

[PB666]

3 hours ago, sgt_flyer said:

safe handling, utter simplicity (no moving parts) for RCS control (granted, more suited for cheap small satellites) - as the propellant extinguish itself when the electric current is removed (and can reignite afterwards if you reapply current). - given the size of the ESP microthrusters, it could even be used on nanosatellites for which it would be utterly impractical to put even a liquid monopropellant RCS system.

You know there are already micro ion systems you can buy, right?

http://busek.com/index_htm_files/70008514E.pdf

ISP 2150. I think this one weighs 53 grams. If you carry 100 grams of fuel you can easily justify the added weight, power utilization 10w. You could have 6 of these on your spacecraft use then as directional thrusters. 300 grams + 200 grams of fuel. All you need is a 2 @ 0.1 meter solar panel and a reasonable battery.

[sgt_flyer]

@PB666 we should look at costs maybe ?  just a PPT unit (much less efficient than busek's rf ion thrusters) for cubesats cost nearly 20000$ - not counting the price of the solar arrays !. (basic cubesat kits can be found for 8000$)

http://www.clyde-space.com/cubesat_shop/propulsion/303_cubesat-pulse-plasma-thruster

http://www.pumpkininc.com/content/doc/forms/pricelist.pdf

 

[fredinno]

4 hours ago, sgt_flyer said:

@PB666 we should look at costs maybe ?  just a PPT unit (much less efficient than busek's rf ion thrusters) for cubesats cost nearly 20000$ - not counting the price of the solar arrays !. (basic cubesat kits can be found for 8000$)

http://www.clyde-space.com/cubesat_shop/propulsion/303_cubesat-pulse-plasma-thruster

http://www.pumpkininc.com/content/doc/forms/pricelist.pdf

 

No reason to suspect exotic solid engines will be much cheaper.

[fredinno]

11 hours ago, AngelLestat said:

I dont like this..  I did not read the paper, but I imaging that the amount of electricity you need to waste is considerable, also... solid propellant...  Those things are just relevant for rocket hobbyist today.
And if you want a solid booster, why make it throttleable?   

Because throttle reduces aerodynamic loads on the rocket, and reduces structural mass, and increases rocket efficiency.

11 hours ago, PB666 said:

I think I posted this in November.

Yes Magnesium and several other metals have advantages over nobel gases as ion drive propellants because, essentially, the are container-less.

ISPs I have seen quoted are in the range of 8000 to 35000 (Vexh = 80000 to 350000 m/s)

We have no effective EPGs to run these systems Solar is too bulky and too heavy per panel length, Nuclear is too heavy and needs to much cooling system mass.

Or let me put it this way, our most effective is solar. Mass grows in spacecraft 3 dimensionally but solar panels grow 2 dimensionally. As a spacecraft grows in radius (such as to accommodate humans) the needed radius of solar panels grows r^3/r^2 or r^1.5. The same is also pretty much true for cooling panels. Its not very long before the radius of the panel exceeds all kinds of things (such as structural limits on extensions, voltage stability for step up transformers and wires).

We have a nice long thread on the perils of ion-based electric powered thrusters. Good for transporting and staging fuel and supplies, not so good for transporting humans.

Higher ISP, very efficient on fuel, very inefficient on power (panel area or nuclear cooling area and mass)

Lower ISP better on acceleration but wastes fuel. Useful only for temporary bursts of speed.

Which is why IONs are most suited for space tugs.

8 hours ago, sgt_flyer said:

better choices ? err... with this kind of ISP and thrust ?? there's not a lot. especially if you have to account for your pressurising gas,solenoid valves, heaters and all the plumbing... (costly to make all that plumbing) limiting satellite costs and improving their reliability is not vain

here's the kind of isp you could get with the power avaible with currently avaible cubesat solar arrays on resistojets ... (50w to 70w...)

http://www.sstl.co.uk/Products/Subsystems/Propulsion-Systems/Low-Power-Resistojet#fragment-3 isp 99s with nitrogen with 50w, and 100mN thrust.

colloid microthrusters, like those on Lisa pathfinder, should be better, but i was not able to find much about their performances.

Militaries love solid propellant, and a throttle-able, restartable solid propellant is amazing for missiles, right next to invisible plume solids.

7 hours ago, RainDreamer said:

Soo...basically C4? Just in a more productive form for space flight?

What's that>

[sgt_flyer]

24 minutes ago, fredinno said:

Because throttle reduces aerodynamic loads on the rocket, and reduces structural mass, and increases rocket efficiency.

Which is why IONs are most suited for space tugs.

Militaries love solid propellant, and a throttle-able, restartable solid propellant is amazing for missiles, right next to invisible plume solids.

What's that>

DSSP have various contracts with nasa, darpa, army, airforce and navy - they plan to go from propellants, gas generators, electric primers, even variable yeld explosives derived from their rocket fuel.

http://dsspropulsion.com/space-defense/development-programs/

- found something on some of their planned engines :

http://dsspropulsion.com/wp-content/uploads/2015/01/DSSP-Cube-Quest-Poster.pdf 

(beware though, it seems the CDM-1 engine is just a classic SRB ;))

Edited March 14, 2016 by sgt_flyer

[shynung]

1 minute ago, sgt_flyer said:

their CDM-1 delta-V engine, would give 50m/s of delta-V to a 4kg 3U cubesat. isp 235s, maximum thrust 186N, (average 76) total weight (engine + fuel) 459g - and only needs 5W of power draw to operate the engine.

For a cubesat thruster, that's actually a respectable performance. Also, that engine lists AP/HTPB as propellant, so presumably what DSSP is developing is some sort of catalyst that works only when zapped. If this is achievable with other AP/HTPB solid rockets, then we can use it for almost anything.

[sgt_flyer]

48 minutes ago, shynung said:

For a cubesat thruster, that's actually a respectable performance. Also, that engine lists AP/HTPB as propellant, so presumably what DSSP is developing is some sort of catalyst that works only when zapped. If this is achievable with other AP/HTPB solid rockets, then we can use it for almost anything.

beware though - this one is a classic single burn srb only

[shynung]

@sgt_flyer

Wait, the AP/HTPB is single-burn? No restarts?

Dang.

Edited March 14, 2016 by shynung

[AngelLestat]

21 hours ago, sgt_flyer said:

better choices ? err... with this kind of ISP and thrust ?? there's not a lot. especially if you have to account for your pressurising gas,solenoid valves, heaters and all the plumbing... (costly to make all that plumbing) limiting satellite costs and improving their reliability is not vain

here's the kind of isp you could get with the power avaible with currently avaible cubesat solar arrays on resistojets ... (50w to 70w...)

http://www.sstl.co.uk/Products/Subsystems/Propulsion-Systems/Low-Power-Resistojet#fragment-3 isp 99s with nitrogen with 50w, and 100mN thrust.

colloid microthrusters, like those on Lisa pathfinder, should be better, but i was not able to find much about their performances.

Those 50W are for few grams of propellant with low isp (less than 100s), the thrust seems fine for that scale (0.1N)
This discard even rocket hobbyist uses and even put into question how good can be for microsats, because we already have many option in thrusting with better numbers:
http://www.tethers.com/HYDROS.html
http://www.busek.com/technologies__ppt.htm
Take a look to the other kind of thrusters too.
I know that solid thrusters can have a benefic in cost, but the product is not developed yet so we dont know nothing about its final cost, but I can agree that it will be cheaper for sure.
Many of the products on that page already include subsystems and stabilization. 

21 hours ago, shynung said:

This is also useful for upper stage kick motors, like Payload Assist Modules, since their throttling capabilities means being able to put the payload satellite into a more precise target orbit than a traditional solid PAM. Also, it's denser than a monopropellant, and doesn't have to carry stuff like plumbing or heaters, so more mass can be dedicated to propellant to offset the specific impulse, which can potentially impart more impulse than a comparable liquid upper stage.

But if you reduce your thrust for higher isp, it allows you extra deltav and extra precision.  I know.. it may be still had some niche.

[shynung]

2 hours ago, AngelLestat said:

But if you reduce your thrust for higher isp, it allows you extra deltav and extra precision.  I know.. it may be still had some niche.

And that extra I_sp demands extra mass for plumbing, power generation, and other subsystems. It's not without its drawbacks. Besides, kicker stages for satellites don't have to expend that much deltaV anyway.

There, that's one niche this propellant can serve in. Granted, not the only one serving it (there are competing propellants), but good enough for this task.

[fredinno]

36 minutes ago, shynung said:

And that extra I_sp demands extra mass for plumbing, power generation, and other subsystems. It's not without its drawbacks. Besides, kicker stages for satellites don't have to expend that much deltaV anyway.

There, that's one niche this propellant can serve in. Granted, not the only one serving it (there are competing propellants), but good enough for this task.

And 100% solid upper stages and military missiles could benefit from this. The former has greater efficiency and better orbital precision.

[shynung]

1 minute ago, fredinno said:

And 100% solid upper stages and military missiles could benefit from this. The former has greater efficiency and better orbital precision.

The missile would need a good battery, no? If the power's cut, it stops burning.

[fredinno]

4 minutes ago, shynung said:

The missile would need a good battery, no? If the power's cut, it stops burning.

Yes, but the advantages outweigh the disadvantages. Missiles today have ramjets, no reason why big batteries are out of the question, considering how much they are improving.

[shynung]

2 minutes ago, fredinno said:

Yes, but the advantages outweigh the disadvantages. Missiles today have ramjets, no reason why big batteries are out of the question, considering how much they are improving.

Ah, the cruise missiles. I was thinking AIM-120 air-to-air missiles. Those still use solids.

Edited March 14, 2016 by shynung

[wumpus]

12 hours ago, shynung said:

@sgt_flyer

Wait, the AP/HTPB is single-burn? No restarts?

Dang.

How did they pull that off?  Best guess is that it kept burning its own leads off, and they gave up trying and went to press with what they had.  Note, it still has uses for final insertion burn/final correction burn (interplanetary), but the initial excitement of a better RCS thruster goes out the window.

I also don't think (even with restarts) it would be all that great for satellite control (PVC thrusters are cheap ion jobs that will eventually get there and you need the solar power anyway) [I'd expect "real" sats to use proper xenon fuel, PVC is pretty inefficient.  If you are even thinking about xenon, solids aren't for you.]

[sgt_flyer]

3 minutes ago, wumpus said:

How did they pull that off?  Best guess is that it kept burning its own leads off, and they gave up trying and went to press with what they had.  Note, it still has uses for final insertion burn/final correction burn (interplanetary), but the initial excitement of a better RCS thruster goes out the window.

I also don't think (even with restarts) it would be all that great for satellite control (PVC thrusters are cheap ion jobs that will eventually get there and you need the solar power anyway) [I'd expect "real" sats to use proper xenon fuel, PVC is pretty inefficient.  If you are even thinking about xenon, solids aren't for you.]

the specific thruster we talked about here is from the brochure it doesn't use dssp's special electric solid fuel   the cmd1 use classic non extinguishible srb propellant  - it's just a cubesat sized srb motor, along with all the needed electronics to start it. (either for a 1 time manoeuver or a deorbit burn) - they currently only made small ESPs (meant to be used as arrays to allow for various thrust levels (you don't need to fire all the esps in the array at the same time). they currently devellop it for RCS control.

[PB666]

48 minutes ago, wumpus said:

How did they pull that off?  Best guess is that it kept burning its own leads off, and they gave up trying and went to press with what they had.  Note, it still has uses for final insertion burn/final correction burn (interplanetary), but the initial excitement of a better RCS thruster goes out the window.

I also don't think (even with restarts) it would be all that great for satellite control (PVC thrusters are cheap ion jobs that will eventually get there and you need the solar power anyway) [I'd expect "real" sats to use proper xenon fuel, PVC is pretty inefficient.  If you are even thinking about xenon, solids aren't for you.]

You could roll out and push the lead across the material, the only problem is the lead becomes part of the ISP, lowering it, meh, if that really matters.

[ChrisDayVACCO]

Is anybody going to the 13th Annual CubeSat Developer’s Workshop?  It is in San Luis Obispo at Cal Poly and there is a information on various types of CubeSat and Nano-Sat propulsion systems there.  There will be a couple hundred people there including students, government and private industry.  Here is a link with more information:

http://www.cubesat-propulsion.com/13th-annual-cubesat-developers-workshop/