Electric Solid Propellants

[shynung]

https://en.wikipedia.org/wiki/Solid-fuel_rocket#Electric_Solid_Propellants

http://arc.aiaa.org/doi/abs/10.2514/6.2013-4168

So apparently this exists now. A solid rocket propellant that can be ignited, throttled, extinguished, and reignited at will by applying an electrical current. I am utterly speechless.

The paper is paywalled, though, so I can't provide much more information at the moment.

What do you think?

[Scotius]

Sounds incredible. Before WW II British Interplanetary Society came up with a lunar mission plan using hundreds of solid boosters of varying sizes to send crew to the Moon. With such fuel building a rocket capable of this feat would be much easier

[sgt_flyer]

Spinsat has been deployed from ISS in 2014 to test out this technology  (it was sent up inside CRS-4)

http://www.nasa.gov/mission_pages/station/research/experiments/1019.html

here's the website of the company who made those used on Spinsat  

http://dsspropulsion.com/technology/works/

here's a video

advantages : safe to handle (solid, and only continuous voltage can work, the propellant does not really react to sparks, heat & flames (unlike classic SRB fuel) and can't make more simple mechanically (ideal for very small sats, to give them RCS capabilities) - density should be correct. (although you need the additionnal dry weight of the casing/nozzle & electrodes) its storable for a long time, and no need to have a pressurizing gas.

i never found any infos on the ISP though.

one small problem if you use one set of those thrusters more than the others on the sat, once the set empty you partially lose your rcs capabilities before you exhausted all the fuel.

 

 

[cantab]

Neat, but I query what advantages it has over resistojets and arcjets for small-scale thrusters. Those are both proven technologies, and arcjets offer much better specific impulse than chemical thrusters.

[sgt_flyer]

39 minutes ago, cantab said:

Neat, but I query what advantages it has over resistojets and arcjets for small-scale thrusters. Those are both proven technologies, and arcjets offer much better specific impulse than chemical thrusters.

guess it needs much less electric power to run than resistojets / arcjets  (2kw of power for a 0.25N arcjet - the solar panels needed for that are really going to be expensive,between costs, size and dry mass - some cubesats solar arrays i've checked give out 56W...) besides, resistojets /arcjets still needs liquid reaction mass - so you still need a pressurising gas to feed your reaction mass to the engines, (and all solenoid valves etc) - ESP really have the potential to minimize devellopment and production costs on very small sats. 

 

 

Edited March 12, 2016 by sgt_flyer

[Scotius]

And even cheap, small launchers (if Isp is decent). Liquid fuel rockets with their expensive plumbing require serious investment, solids are simpler.

[sgt_flyer]

1 hour ago, Scotius said:

And even cheap, small launchers (if Isp is decent). Liquid fuel rockets with their expensive plumbing require serious investment, solids are simpler.

guess it'll also depend on the costs of the fuel itself, once it reaches high enough production to see economy of scale. but it might be interesting to use it for at least the upper stage of an all solid rocket  - with it's multiple firing capabilities and ability to stop it, along with the fact it's storable - simple, reliable & effective upper stage capable of high precision

[problemecium]

Is it squishy? Or does it melt at a temperature below its ignition temperature?
Because if so that could solve the asymmetrical RCS problem. If one thruster has significantly more fuel than another, perhaps a soft or molten glob could be redistributed among the two.

[jf0]

The paper claims Isp from 225 upto 260, but it also contains several editing errors and liberal use of the trademark 'TM' symbol, which to me gives it the appearance of nonsense (but thats just me....)

[sgt_flyer]

1 hour ago, parameciumkid said:

Is it squishy? Or does it melt at a temperature below its ignition temperature?
Because if so that could solve the asymmetrical RCS problem. If one thruster has significantly more fuel than another, perhaps a soft or molten glob could be redistributed among the two.

depends if it can keep it's properties once melted, or if it decomposes into it's constituants.

mmh, from a paper about those, seems that without active cooling, they expect duty cycles <20% - so guess heat management may be an issue

http://digitalcommons.usu.edu/cgi/viewcontent.cgi?article=1887&context=smallsat

 

[fredinno]

9 hours ago, shynung said:

https://en.wikipedia.org/wiki/Solid-fuel_rocket#Electric_Solid_Propellants

http://arc.aiaa.org/doi/abs/10.2514/6.2013-4168

So apparently this exists now. A solid rocket propellant that can be ignited, throttled, extinguished, and reignited at will by applying an electrical current. I am utterly speechless.

The paper is paywalled, though, so I can't provide much more information at the moment.

What do you think?

What's the cost? It could be useful for Orbital ATK's SRBs once it can get going.

3 hours ago, sgt_flyer said:

guess it'll also depend on the costs of the fuel itself, once it reaches high enough production to see economy of scale. but it might be interesting to use it for at least the upper stage of an all solid rocket  - with it's multiple firing capabilities and ability to stop it, along with the fact it's storable - simple, reliable & effective upper stage capable of high precision

Well, I expect economy of scale very soon, considering it is storable and much more controllable than old SRB designs. Imagine the flexibility of a ramjet-electric solid propellant missile! Imagine a missile intelligently turning off after being deployed from a plane, like a dud, only to turn back on when right underneath a enemy plane!

[shynung]

@fredinno

That, I don't know much, unfortunately. I do think using it as SRB propellant would be great, though. Especially the upper stages.

[YNM]

I think these things would rather be used for main propellant. Direction control could be done by some gyros... Also, if some parts ran out of propellant, you can just rotate so the working set faces the needed direction and off you go !

[sgt_flyer]

@YNM

gyros in real life aren't like in ksp  they don't give you unlimited rotation capability (once they are saturated you need to respin them creating countertorque in the spacecraft ) (also, they take space & dry mass too ;))

still, the figures they give still states low ISPs, between 220s and 260s. -  depending on the fuel density, (which might be a bit lower than classic SRBs), it's not necessary a good thing for longevity. (something really sought after in large commsats)for cubesats and smaller small satellites though, it could give them low cost propulsion capability where the alternatives where either pricy or even inexistent, giving a lot more interest in low cost smallsats.

though, there's adversaries coming up in hypergolic liquid propellants too.

LMP-103s and AF-M315E for storable monopropellants - those have better ISP than hydrazine, better density, and much lower toxicity (they don't need heavy protective gear for fueling, and can transport the stuff by plane - that low toxicity alone would already reduce satellite preparation costs by a lot - personnel safeties cost a lot of time and money). 

http://enu.kz/repository/2009/AIAA-2009-4878.pdf

https://www.rocket.com/files/aerojet/documents/Capabilities/PDFs/GPIM%20AF-M315E%20Propulsion%20System.pdf

Edited March 12, 2016 by sgt_flyer

[shynung]

@YNM

What you're looking for, if you want to gimbal it, would be a set of exhaust vanes, like this old V2.

They're less effective than a gimballed nozzle assembly, but much simpler.

[AngelLestat]

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?   

[PB666]

On 3/11/2016 at 1:46 AM, shynung said:

https://en.wikipedia.org/wiki/Solid-fuel_rocket#Electric_Solid_Propellants

http://arc.aiaa.org/doi/abs/10.2514/6.2013-4168

So apparently this exists now. A solid rocket propellant that can be ignited, throttled, extinguished, and reignited at will by applying an electrical current. I am utterly speechless.

The paper is paywalled, though, so I can't provide much more information at the moment.

What do you think?

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.

Edited March 13, 2016 by PB666

[sgt_flyer]

14 minutes 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.

 

@PB666 the paper linked by Shynung is about Digital Solid State Propulsion technology (the one used for Spinsat)  - they formulated a solid material that stays ignited only while applying constant electric power (ISPs cited between 220s and 280s. basically a safe controllable SRB fuel  - as it doesn't ignite under flames or sparks)

edit : here's spinsat aboard ISS, before it was released from iss.

given the size of the thing, i doubt power requirements are on the same order as those needed for vaporising metals

Edited March 13, 2016 by sgt_flyer

[PB666]

17 minutes ago, sgt_flyer said:

@PB666 the paper linked by Shynung is about Digital Solid State Propulsion technology (the one used for Spinsat)  - they formulated a solid material that stays ignited only while applying constant electric power (ISPs cited between 220s and 280s. basically a controllable SRB

 

 

Whats the point of it then?

 

[sgt_flyer]

12 minutes ago, PB666 said:

Whats the point of it then?

 

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.

Edited March 13, 2016 by sgt_flyer

[shynung]

39 minutes 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?   

sgt_flyer explained it better than me in the post above.

[AngelLestat]

1 hour ago, shynung said:

sgt_flyer explained it better than me in the post above.

those are were concerns of the past, it does not worth it today.
And I was agree with @cantab answer, there are better choices for small sats. 
but well, maybe there is still a niche that I am not seeing. 

Edited March 13, 2016 by AngelLestat

[sgt_flyer]

31 minutes ago, AngelLestat said:

those are were concerns of the past, it does not worth it today.
And I was agree with @cantab answer, there are better choices for small sats. 
but well, maybe there is still a niche that I am not seeing. 

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.

Edited March 13, 2016 by sgt_flyer

[shynung]

1 hour ago, AngelLestat said:

those are were concerns of the past, it does not worth it today.
And I was agree with @cantab answer, there are better choices for small sats. 
but well, maybe there is still a niche that I am not seeing. 

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.

Edited March 13, 2016 by shynung

[RainDreamer]

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