Author Topic: Next best propellant for abort engines after hydrazine et al  (Read 11026 times)

Offline adrianwyard

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I couldn't find the answer to this elsewhere so apologies it's common knowledge.

If hypergolics like hydrazine and nitrogen tetroxide were for some reason eliminated from a future vehicle, what would be the next best alternative propellant? Let's assume the task is abort engines, so mass, volume, and reliability/simplicity are still paramount.  Is anything close?

To my knowledge SNC is the only company proposing to use something other than hypergolics or solids for this purpose, with their propane/nitrous Orbitek engine. Anyone care to guess how that might perform compared to the others?

Offline Burninate

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It sounds like the question you're trying to ask might need some more constraints.

Hydrogen/LOX, kerosene/LOX, methane/LOX, and solids are all propellant options, but they are not really propellant options to directly replace hydrazine & NTO, they're not in the running for the much-vaunted 'green propellant'.  That's because LOX is mildly cryogenic and storing it long-term is a moderately complicated engineering problem we have not tackled in orbit yet, & the solutions are quite likely to only going to be worthwhile for large propellant volumes.  Hydrazine/NTO, hydrazine-based monopropellant, and inert nitrogen monopropellant, by contrast, are storeable at routine temperatures and pressures indefinitely, and permit extremely simple, lightweight, low-thrust engines.  These are engines that are small enough to spread out over the craft and use for RCS & in-space maneuvering fuel.

Only a few rockets still use hydrazine for any purpose other than tiny orbital thrusters - the Proton and some of the other Russian LVs.

So -
What type of ignition?
Monoprop or biprop?
How many vacuum restarts are permitted?
What type of Isp?
How thermally stable?

There are, as I understand it, a lot more fuels in the possibility space than there are oxidizers, so might as well start there.
« Last Edit: 03/14/2015 08:38 PM by Burninate »

Offline nadreck

Hydrogen peroxide/RP-1 it could easily be used for both RCS systems and larger engines. Alternately hydrogen peroxide and RP-1 for a high thrust engine and just hydrogen peroxide for RCS.

Drawbacks of H2O2 are instability at high temps and a freezing point near the same as water. Advantages are self ignition with RP-1 and many other fuels, and relatively high density.
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Offline adrianwyard

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Thanks, Burninate. I was thinking of limiting the question to just abort motors - where hydrazine is very much in use today (SpaceX Dragon, CST-100, Blue Origin).

Offline Damon Hill

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Offline Burninate

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Random notes on oxidizers from half an hour of googling:

So for conventional oxidizers, we have:
NTO, nitrogen tetroxide - problematically toxic, the standard in orbital maneuvering and also used in some liquid LVs
LOX, liquid oxygen - problematically cryogenic, the standard in liquid LVs
AP, ammonium perchlorate - mildly toxic, the standard in solid rockets
N2O, Nitrous oxide - pushed as bipropellant, as hybrid rocket oxidizer, and mixed into blended fuels as "NOFBX" liquid monopropellant, one of NASA's favorites to replace hydrazine/NTO
HTP - high test peroxide - Used frequently early in rocketry, but unless refrigerated, prone to runaway thermal autodecomposition

http://www.redalyc.org/articulo.oa?id=309429107002 puts forward:
ADN - Ammonium Dinitramide, fingered for replacing both the AP in solids and the hydrazine in liquid monopropellant, as part of an oxidizer-fuel blend
HNF - Hydrazinium Nitroformate, higher performance for solid rockets but needs research on stabilizing it

Next year NASA is launching the Green Propellant Infusion Mission, GPIM, using:
" a Hydroxyl Ammonium Nitrate (HAN) fuel/oxidizer blend, or AF-M315E."

http://www.spg-corp.com/nytrox-propellants.html & http://enu.kz/repository/2009/AIAA-2009-4966.pdf is trying to sell
Nytrox, nitrous oxide - LOX blends, pushed as self-pressurizing oxidizer for hybrid sounding rockets

http://adsabs.harvard.edu/full/2004ESASP.557E..23D pushes
AN, Ammonium Nitrate, as a cheaper, greener replacement or partial replacement for AP in solid rockets, and also as a solitary monopropellant.

http://www.diva-portal.org/smash/get/diva2:360054/FULLTEXT01.pdf works primarily towards stabilizing ADN, and notes six potential oxidizers, of which TNA / trinitramide seems to be their focus:
Quote
The dinitramide (1), trinitrogen dioxide (75), pentazole (77), oxopentazole (78), 1,3-dioxopentazole (79)
and the 1-nitro-2-oxo-3-aminotriazene (76) anions all hold considerable promise in all these respects. Finally, the neutral trinitramide molecule (25), the largest all-nitrogenoxygen compound known, was successfully synthesized and characterized
Trinitramide had been theorized long before being formulated.

Wikipedia's article on Monopropellants lists under new developments HAN, and an adaptation of ADN:
Quote
The EURENCO Bofors company produced LMP-103S as a 1-to-1 substitute for hydrazine by dissolving 65% ammonium dinitramide, NH4N(NO2)2, in 35% water solution of methanol and ammonia. LMP-103S has 6% higher specific impulse and 30% higher impulse density than hydrazine monopropellant. Additionally, hydrazine is highly toxic and carcinogenic, while LMP-103S is only moderately toxic. LMP-103S is UN Class 1.4S allowing for transport on commercial aircraft, and was demonstrated on the Prisma satellite in 2010. Special handling is not required. LMP-103S could replace hydrazine as the most commonly used monopropellant.[4]

It seems NOFBX had manifested a mission for 2013, but it may have been delayed or cancelled, while the HAN-fuel blend was the second green propellant to manifest an experimental mission (launch in 2016).

There's also testing of a water ice - nano-aluminum blend.

SO:
The commercially developed options for new liquid monoprop fuel blends seem to be LMP-103S (ADN/fuel), AF-M315E (HAN/fuel), and NOFBX (N2O/fuel).
« Last Edit: 03/14/2015 09:55 PM by Burninate »

Offline cdleonard

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As far as I know the Boeing CST-100 will actually use a LOX/alcohol engine. Is wikipedia wrong about this?
« Last Edit: 03/14/2015 09:51 PM by cdleonard »

Offline kevin-rf

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You also have the option of white fuming nitric acid. It is hypergolic and not nearly as toxic as other options. You would not want to spoil it on your new shoes, but it is considered safer....

There once was an nsf thread extolling it's virtues. Five minutes with the search engine should find it.
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Offline Port

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http://en.wikipedia.org/wiki/Green_Propellant_Infusion_Mission

this!
IL's are amazing substances and chemists are barely touching the surface of what's possible (I'm working in this area)
The framework they exhibit in liquid state (yes thats the weird thing about them) makes them ideal for kinetically stabilizing something that seriously want's to go ooompf (like that Hydroxyl-Group on the nitrogen, man that one is really unhappy).

Offline adrianwyard

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As far as I know the Boeing CST-100 will actually use a LOX/alcohol engine. Is wikipedia wrong about this?

I heard Boeing switched to hypergols for the RS-88 on CST-100, but after some googling the only sources I can find for that are here at NSF, so I'm really not sure. CCDev 1 Milestone B4 looks like it might have been related to this switch, but I can't find anything definitive.

I suppose using LOX - or any cryogen - in an abort system adds the problem of boil-off and/or some means to replenish it.

Offline cdleonard

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Also, aren't disposable solids sort of ideal for an abort engine? Cheap and high-thrust.

The reason Dragon 2 is using hypergols is because they want to use the same engines to land propulsively even after spending months in space. It can also share the fuel with the attitude control system.

I guess CST-100 is using a liquid-fueled abort system because it's reusable?

Offline adrianwyard

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I guess CST-100 is using a liquid-fueled abort system because it's reusable?

That can't be the reason: the service module is discarded each flight.

A liquid/pusher abort system has the advantage (over solids) of being available for orbital maneuvering and de-orbit. But then storability is key, so cryogens are a problem.
« Last Edit: 03/14/2015 11:49 PM by adrianwyard »

Offline dkovacic

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I would also vote for HTP/RP-1, because HTP can be used for multiple purposes for any HSF mission (source of water, oxygen, fuel cell, mono-prop RCS). ISP is approximately the same as for NTO/MMH combination.

Let me put this this way - imagine being stuck in spaceship without propulsion, with days or weeks before any rescue mission can reach you. Which of chemicals mentioned above would you want to have in the tanks?

Offline RanulfC

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I would also vote for HTP/RP-1, because HTP can be used for multiple purposes for any HSF mission (source of water, oxygen, fuel cell, mono-prop RCS). ISP is approximately the same as for NTO/MMH combination.

Let me put this this way - imagine being stuck in spaceship without propulsion, with days or weeks before any rescue mission can reach you. Which of chemicals mentioned above would you want to have in the tanks?

While I agree with the first part I need to point out that the second part probably doesn't even matter as unless the systems is PLUMBED for access you can't GET to propellant in the tanks for use anyway :) I'm not sure anyone would consider it "cost-effective" to plumb a system for access on the off chance you 'might' need it at some point however if you've been designing for such operations as propellant transfer the chances go up greatly :)

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Offline Patchouli

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I would also vote for HTP/RP-1, because HTP can be used for multiple purposes for any HSF mission (source of water, oxygen, fuel cell, mono-prop RCS). ISP is approximately the same as for NTO/MMH combination.

Let me put this this way - imagine being stuck in spaceship without propulsion, with days or weeks before any rescue mission can reach you. Which of chemicals mentioned above would you want to have in the tanks?
It would be a good choice since it is relatively storable and everything is liquid at normal temperatures and pressures.
The only bad part is contamination of the HTP though you have to keep NTO and MMH free of any contamination as well so it doesn't really introduce many new issues.
As for use in OMS long term storage would not be an issue Soyuz has HTP thrusters in it's decent module and has no problems staying six months at ISS.
 
Even though they seem to come up short for sub orbital spacecraft is N2O rubber hybrids might be another ideal propellant for abort systems that double as OMS.

The minimum 1.7KM/sec of delta V a sub orbital spacecraft like SS2 needs to reach 100km is a ridiculous overkill for an abort motor.

« Last Edit: 04/25/2015 05:26 AM by Patchouli »

Offline adrianwyard

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...
Even though they seem to come up short for sub orbital spacecraft is N2O rubber hybrids might be another ideal propellant for abort systems that double as OMS.

The minimum 1.7KM/sec of delta V a sub orbital spacecraft like SS2 needs to reach 100km is a ridiculous overkill for an abort motor.

I recall people were critical of Dream Chaser's use of HTPB/Nitrous for its abort engines (which were also used for OMS and de-orbit). A couple of the factors were: thrust and startup time (in the case of abort, spare delta V is of no use if you can't use it to get out of dodge quickly). I'm not sure how fair a criticism this was, but we do know that the thrust to weigh ratio of Dragon's abort solution was far higher than DC's.

The last we heard from SNC is that they'd switched to Propane/Nitrous. I'm not sure if that combination fairs any better in terms of high-thrust in short order.
« Last Edit: 04/26/2015 09:31 PM by adrianwyard »

Offline adrianwyard

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Minor addition: A little googling confirms that UDMH and N2O4 are not shock sensitive, so any replacement would ideally match that quality.

That info came from the following useful brief description of propellants: http://www.astronautix.com/props/index.htm

Offline dafeixue001

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I'm paying attention to nofbx, I think it's a promising propellant .I haven't got any information about it since 2013.
 

Offline Rei

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I would also vote for HTP/RP-1, because HTP can be used for multiple purposes for any HSF mission (source of water, oxygen, fuel cell, mono-prop RCS). ISP is approximately the same as for NTO/MMH combination.

Let me put this this way - imagine being stuck in spaceship without propulsion, with days or weeks before any rescue mission can reach you. Which of chemicals mentioned above would you want to have in the tanks?

I don't think you're going to be arbitrary tapping into tanks in space and building homemade catalyst beds for decomposition, even in an emergency.  Unless the tank had some sort of system specifically designed for recovery of oxygen and water. In which case, why did you spend the money and launch mass building such a system rather than a proper water recovery / O2 generating life support system that's useful all the time?

Plus, it's technically possible to make life-support-useful compounds out of almost any propellant combination - run them over a hot platinum catalyst and you'll generally get a steady feed of their exhaust products, which often contain at the very least H2O, which you're probably splitting anyway in an oxygen generator. That doesn't mean that it's justifiable to include a system to do so, unless it's serving some other purpose (for example, using propellant in a fuel cell for power generation)

Really, though, my main issue with HTP is that it's explosive if you do anything wrong. There've been too many HTP handling accidents for my comfort. ISP is pretty bad, too.
« Last Edit: 03/26/2017 01:00 PM by Rei »

Offline Rei

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Minor addition: A little googling confirms that UDMH and N2O4 are not shock sensitive, so any replacement would ideally match that quality.

That info came from the following useful brief description of propellants: http://www.astronautix.com/props/index.htm

One additional thing I like about MON (aka what most people mean when they talk about N2O4) is that it works well with hydrogen free and low-hydrogen fuels. These tend to burn very hot. However, if you burn for example cyanogen with MON instead of LOX it drops the flame temperature by something like 300 degrees, at a cost of only something like 10 sec ISP (while gaining the other benefits of MON - non-cryogenic, high density, self-pressurizing, hypergolic with many fuels, etc). The ISP drop is much lower than when you burn MON with hydrogen-rich fuels. As for temperature, the extra nitrogen in the oxidizer helps dilute the exhaust, yielding more moles of lower temperature gas rather than fewer moles of higher temperature gas. Also, unlike advanced oxidizers, it remains fairly simple to synthesize in ISRU environments. If you're making fertilizer or the basic industrial acids locally, you've got MON (N2 + 3 H2 -> 2 NH3 (Haber), 4 NH3 + 5 O2 -> 4 NO + 6 H2O (Ostwald stage 1), 2 NO + O2 -> 2 NO2 (Ostwald stage 2); NO2 dimerizes to N2O4)
« Last Edit: 03/26/2017 12:54 PM by Rei »

Offline Proponent

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I'm paying attention to nofbx, I think it's a promising propellant .I haven't got any information about it since 2013.

My guess would be that 2013 is when Firestar realized that NOFBX was not going to work.  In retrospect, it does seem too good to be true.

EDIT:  "wasn't not" -> "was not"
« Last Edit: 03/28/2017 11:06 PM by Proponent »

Offline brickmack

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A few people have mentioned AF-M315E, the GPIM propellant. This is a very promising option for satellite propulsion (high ISP, high density, more easily storable than most other fuels, cheap), but isn't close to relevant to OPs question. The most powerful thruster in serious development so far with that propellant produces a whopping 22 newtons of thrust, you can never achieve a TWR greater than 1 with engines of that size even if you used thousands of them. Maybe in a few decades someone will come up with something, but for now there is zero design history relevant to an abort motor, and not even any concepts I can find for how to make such a thing work
« Last Edit: 03/26/2017 10:04 PM by brickmack »

Offline savuporo

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Just go with LMP-103S. Space qualified, and has actual commercial wins
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Offline sevenperforce

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The water weight of HTP makes it very very thrusty when used to oxidize hydrocarbons (with which it is hypergolic), and its decomposition can be used to run a turbopump off a catalyst, so it seems like a pretty good solution all-around.

Offline Arch Admiral

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H2O2 has a safety record far worse that hydrazine or N2O4. It was strongly promoted by one Dr. Helmut Walter in Nazi Germany, and was widely copied around the world due to the unjustified reputation German engineering had in those days. The problem is that it blows up on contact with anything organic plus a lot of common metals. It has been dropped in torpedos, in submarine engines, and in military missiles. NASA dropped it after Mercury. The UK rocket program dropped in the 1950s. Probably the worst H2O2 disaster was RNS KURSK.

The only remaining user is Roscosmos, in the Soyuz & Progress thrusters and the R-7 booster turbopumps. They just don't have the money to replace it.

This whole "green propellant" movement is really a push for "nontoxic propellant" and is based on an exaggerated fear of the conventional fuels. In the space shuttle program there was one serious spill  that zorched a few tiles, and one leak that kept a crew shut up in the Orbiter for 90min after landing. Pretty good for 135 missions.

Offline brickmack

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This whole "green propellant" movement is really a push for "nontoxic propellant" and is based on an exaggerated fear of the conventional fuels. In the space shuttle program there was one serious spill  that zorched a few tiles, and one leak that kept a crew shut up in the Orbiter for 90min after landing. Pretty good for 135 missions.

Beyond the risk of an accident, working with such horrendously toxic propellants still just isn't cheap. The safety requirements significantly increase costs, I've seen cost figures in the low millions for fueling a typical spacecraft, almost all of which is related to safety accommodations rather than the material itself (though those WERE studies by companies involved in green propellants, so maybe a bit of exaggeration). If you can get rid of that, it would bring down the cost a lot

Its also more generally a push for new propellants, which just happen to be friendlier to work with. Theres been very little serious research into new spacecraft propellants in ages even though relevant fields have advanced so much in that time. Its not a coincidence that most of these "green" propellants also are denser, easier to store, and more efficient than the current norm

Offline savuporo

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..Beyond the risk of an accident, working with such horrendously toxic propellants still just isn't cheap.
And that's both operational cost which are more often quoted, but also development costs. Developing and qualifying hydrazine thusters isnt cheap.
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Offline sevenperforce

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H2O2 has a safety record far worse that hydrazine or N2O4. It was strongly promoted by one Dr. Helmut Walter in Nazi Germany, and was widely copied around the world due to the unjustified reputation German engineering had in those days. The problem is that it blows up on contact with anything organic plus a lot of common metals. It has been dropped in torpedos, in submarine engines, and in military missiles. NASA dropped it after Mercury. The UK rocket program dropped in the 1950s. Probably the worst H2O2 disaster was RNS KURSK.
Oh, yes, it's very nasty stuff if you make the mistake of treating it carelessly.

Offline speedevil

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The water weight of HTP makes it very very thrusty when used to oxidize hydrocarbons (with which it is hypergolic), and its decomposition can be used to run a turbopump off a catalyst, so it seems like a pretty good solution all-around.

I'm fairly sure that HTP isn't hypergolic - that is, self-igniting, with hydrocarbons in rocket use.

All of the research I found on this when looking at it about a decade ago all agreed that either an ignitor or catalyst pack was needed.
You can't just spray H2O2 and kerosene and have it ignite. (at least not other than as a possible accident)

Offline sevenperforce

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The water weight of HTP makes it very very thrusty when used to oxidize hydrocarbons (with which it is hypergolic), and its decomposition can be used to run a turbopump off a catalyst, so it seems like a pretty good solution all-around.

I'm fairly sure that HTP isn't hypergolic - that is, self-igniting, with hydrocarbons in rocket use.

All of the research I found on this when looking at it about a decade ago all agreed that either an ignitor or catalyst pack was needed.
You can't just spray H2O2 and kerosene and have it ignite. (at least not other than as a possible accident)
Well, yeah, cold HTP won't ignite on contact with RP-1, but a reusable catalyst will do the trick. It's a lot closer to hypergolic performance than to systems which require a separate ignitor.
« Last Edit: 04/05/2017 01:44 PM by sevenperforce »

Offline smfarmer11

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Well as far as simplicity goes, you can't really beat a solid fuel system. Solid rockets are extremely reliable , quick to start. Although I feel that's against the tide of this thread.

Offline brickmack

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Well as far as simplicity goes, you can't really beat a solid fuel system. Solid rockets are extremely reliable , quick to start. Although I feel that's against the tide of this thread.

Not reusable or testable, dead mass in a nominal flight, dangerous to work with on the ground, and tends to result in excessive acceleration.

Offline Jim

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Well as far as simplicity goes, you can't really beat a solid fuel system. Solid rockets are extremely reliable , quick to start. Although I feel that's against the tide of this thread.

Not reusable or testable, dead mass in a nominal flight, dangerous to work with on the ground, and tends to result in excessive acceleration.

Just like ejection seats.  So what is your point?

Offline Patchouli

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Well as far as simplicity goes, you can't really beat a solid fuel system. Solid rockets are extremely reliable , quick to start. Although I feel that's against the tide of this thread.

Not reusable or testable, dead mass in a nominal flight, dangerous to work with on the ground, and tends to result in excessive acceleration.

Solid abort motors do not necessarily have to be dead mass dead mass during a nominal flight
The Kliper space craft would,have fired it's abort motors in pairs to help with orbital insertion.
http://www.russianspaceweb.com/kliper_history.html
« Last Edit: 05/05/2017 03:29 AM by Patchouli »

Online Katana

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For abort engines only, solids are good enough since Apollo.

For multi purpose engines, just roll back to WRFNA+Amines,standard hypergolics in 1950s before more toxic NTO+MMH.
Somewhat low performance, but yet higher performance than AF-M315E monopropellant.

NOFBX is a mixture of liquefied N2O and hydrocarbon gas, more horribly spontaneously explosive than H2O2.
N2O itself is a spontaneously explosive monopropellant (the SpaceShip2 explosion in 2007).

Offline Dante80

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A few people have mentioned AF-M315E, the GPIM propellant. This is a very promising option for satellite propulsion (high ISP, high density, more easily storable than most other fuels, cheap), but isn't close to relevant to OPs question. The most powerful thruster in serious development so far with that propellant produces a whopping 22 newtons of thrust, you can never achieve a TWR greater than 1 with engines of that size even if you used thousands of them. Maybe in a few decades someone will come up with something, but for now there is zero design history relevant to an abort motor, and not even any concepts I can find for how to make such a thing work

Coming back to this, if the concept is tested and works as advertised, what would be the problem with scaling this up? If it is under consideration for military missiles, can't it not work in something like a SuperDraco class setting?

What I am asking is whether the problem is simply TRL for scaling (someone needs to pay and work on this) or a hard blocker in scaling all-together (like electric propulsion requiring ridiculous amounts of electricity to do serious thrust).
« Last Edit: 06/10/2017 06:53 PM by Dante80 »

Offline brickmack

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Coming back to this, if the concept is tested and works as advertised, what would be the problem with scaling this up?

...

The big problem I was thinking of those is that this is a catalytic monopropellant, you've got to get the entire propellant stream to contact the catalyst bed. Thrust scales roughly with propellant volume, but the volume of propellant that can be usefully burned scales with surface area. Thats a problem. Hypergolic bipropellants are easy by comparison, just contact the 2 chemicals together. I don't know how quickly this will stop scalability, but given we're talking roughly a 4000x scaling factor between the current "high thrust" GR-22 and SuperDraco, I'd be surprised if it'll scale *that* far.

Do you have any information on it being used in missiles? I couldn't find anything on the subject. I'd take a guess (given that the US military has long preferred solid fueled missiles for a variety of reasons) this is just for roll control thrusters or a final targetting upper stage, neither of which needs thrust hugely greater than whats already demonstrated

Online Katana

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Coming back to this, if the concept is tested and works as advertised, what would be the problem with scaling this up?

...

The big problem I was thinking of those is that this is a catalytic monopropellant, you've got to get the entire propellant stream to contact the catalyst bed. Thrust scales roughly with propellant volume, but the volume of propellant that can be usefully burned scales with surface area. Thats a problem. Hypergolic bipropellants are easy by comparison, just contact the 2 chemicals together. I don't know how quickly this will stop scalability, but given we're talking roughly a 4000x scaling factor between the current "high thrust" GR-22 and SuperDraco, I'd be surprised if it'll scale *that* far.

Do you have any information on it being used in missiles? I couldn't find anything on the subject. I'd take a guess (given that the US military has long preferred solid fueled missiles for a variety of reasons) this is just for roll control thrusters or a final targetting upper stage, neither of which needs thrust hugely greater than whats already demonstrated
https://www.rocket.com/files/aerojet/documents/Capabilities/PDFs/GPIM%20AF-M315E%20Propulsion%20System.pdf
AF-M315E offers higher performance than hydrazine, yields 12% higher Isp (257 vs. 235 sec)
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Isp only better than monoprop hydrazine (catalytic decompose), yet much inferior than biprops.

Offline Nilof

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The water weight of HTP makes it very very thrusty when used to oxidize hydrocarbons (with which it is hypergolic), and its decomposition can be used to run a turbopump off a catalyst, so it seems like a pretty good solution all-around.

I'm fairly sure that HTP isn't hypergolic - that is, self-igniting, with hydrocarbons in rocket use.

All of the research I found on this when looking at it about a decade ago all agreed that either an ignitor or catalyst pack was needed.
You can't just spray H2O2 and kerosene and have it ignite. (at least not other than as a possible accident)

Hot decomposed HTP is hypergolic with Kersosene though. Any fuel-oxidizer composition is hypergolic if you just make the temperature high enough.  ;)
For a variable Isp spacecraft running at constant power and constant acceleration, the mass ratio is linear in delta-v.   Δv = ve0(MR-1). Or equivalently: Δv = vef PMF. Also, this is energy-optimal for a fixed delta-v and mass ratio.

Offline John-H

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The water weight of HTP makes it very very thrusty when used to oxidize hydrocarbons (with which it is hypergolic), and its decomposition can be used to run a turbopump off a catalyst, so it seems like a pretty good solution all-around.

I'm fairly sure that HTP isn't hypergolic - that is, self-igniting, with hydrocarbons in rocket use.

All of the research I found on this when looking at it about a decade ago all agreed that either an ignitor or catalyst pack was needed.
You can't just spray H2O2 and kerosene and have it ignite. (at least not other than as a possible accident)

Hot decomposed HTP is hypergolic with Kersosene though. Any fuel-oxidizer composition is hypergolic if you just make the temperature high enough.  ;)

Once the engine is running, do you still need a catalyst. I can't picture HTP going into a fully burning hot engine and  putting the fire out.

John

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