Author Topic: "Diesel" type rocket engine?  (Read 28391 times)

Offline mmeijeri

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Re: "Diesel" type rocket engine?
« Reply #20 on: 03/16/2010 04:11 pm »
A related question: have blended fuels ever been seriously considered for rocket applications? I'm thinking of adding something like hydrazine or ammonia with relatively low molecular weight combustion products to fuel with relatively heavy ones like silane? Could you optimise Isp that way?
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Offline FinalFrontier

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Re: "Diesel" type rocket engine?
« Reply #21 on: 03/16/2010 04:14 pm »
A related question: have blended fuels ever been seriously considered for rocket applications? I'm thinking of adding something like hydrazine or ammonia with relatively low molecular weight combustion products to fuel with relatively heavy ones like silane? Could you optimise Isp that way?
Perhaps. I am sure some research has been done on it. But its not just Isp IMO, at least, for the first stage. Its also: how much thrust can you generate with a given mixture of two, three, even four propellants as opposed to other mixtures? Whats the best one? I truly think though that a TAN using ethier rp1 or something else, or both, should be the future. Just Lox and Lh2, or Lox and rp1 is old tech. If a TAN design can be made that is better than mixtures of more than two propellants ought to be where the future is. But again, I am only talking first stage stuff.
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Offline mmeijeri

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Re: "Diesel" type rocket engine?
« Reply #22 on: 03/16/2010 04:17 pm »
Well, for off Earth applications thrust would be less important. What you say is certainly important, but there are scenarios where Isp is more important than thrust as well.
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Offline FinalFrontier

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Re: "Diesel" type rocket engine?
« Reply #23 on: 03/16/2010 04:27 pm »
Well, for off Earth applications thrust would be less important. What you say is certainly important, but there are scenarios where Isp is more important than thrust as well.
Exactly. Off earth is more about isp by far. VASIMIR is the ideal set up IMO. Perhaps by mixing in other gases besides argon you could boost output?
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Offline mmeijeri

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Re: "Diesel" type rocket engine?
« Reply #24 on: 03/16/2010 04:31 pm »
Planetary capture/descent/ascent would be somewhere in between, this would need far more thrust than VASIMR but Isp would still be important.
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Offline JasonAW3

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Re: "Diesel" type rocket engine?
« Reply #25 on: 03/16/2010 05:32 pm »
I can think of one potential application, far in the future: a lander engine capable of running on both LOX/methane and LOX/silane.

Not to derail this, but I've seen you mention silane a few times. Isn't it a problem that half of the combustion product (by weight) is silicon dioxide or silicon monoxide? Wouldn't you have massive efficiency losses because you're trying to expand a flow where half of the mass flow is in entrained solid particles? Not to mention your nozzle being sandblasted.

      Not to ruin a pretty good point, but Silane is a gas.  It pretty much matches the same molecular structure as Methane, but with silicon in place of Carbon.  Unlike Methane, though, Silane will automatically combust in the presence of Oxygen.  (Saves on the igniter costs)
      Unless ethane has a similar ISP to Methane, Silane would be a good choice for a fuel as its' ISP are very close to that of Methane.

     As to the "Diesel" concept, yes I meant an engine that can run on multiple fuel types, not strictly on "Diesel" fuel.  (I understand that diesel fuel ISP would likely be very low).
     I suspect that the simplest solution would be some sort of pressure fed enging that doesn not require any sort of pumps per se, but could use a Nitrogen or Helium bladder in the fuel and oxidizer tanks to provide the needed pressure for feed to the engine.

     I didn't know aboutthe RL-10's flexibility, but what I had in mind was a set of different motors, designed at different scales that could use a variety of fuels, depending upon the payload needs and cost factors of fuel and launch vehicle costs.
     What I am saying is that we develop engines and rockets that can use a variety of fuels dependant upon the mission and ayload requirements.  By being able to mass produce a series of different scaled rockets that would have a range of payload masses to orbit, depending upon the fuels and oxidizers used.  By using a standardized rocket format, with fuel flexibility, it was my thinking that costs could be lowered by shear volume of production of the hardware.  Obviously, there would be comprimizes of ISP depending upon combustion chamber configurations, exhaust nozzels, etc, but the overall cost savings should be substantile enough to compensate for this.
      As to the "Conversion Kits", what I had in mind was a series of injectors and igniters that could be, relatively, easily changed out to accomidate the different fuel types while using a standardized motor and stage design.

     Well, that's what I was thinking, for what it's worth.

Jason
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Offline JasonAW3

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Re: "Diesel" type rocket engine?
« Reply #26 on: 03/16/2010 05:36 pm »
I just wanted to add: I once looked at the possibility of using a liquid parafin wax/aluminum emulsion burning with liquid oxygen as a very high-impulse density propellant. Trouble with this is that again, you have to insulate both tanks very well, and tens of thousands of gallons of hot wax and aluminum are going to radiate a heck of a lot of heat and couple it to 60,000 gallons or so of liquid oxygen. Refrigeration and heating in very close proximity is really complicated!

Also pressure drop in pintel injector is ferocious, not to mention the pumping power needed for moving a thick, dense slurry. And the need for an auxiliary jet pump to keep the fuel emulsion stirred up so the aluminum doesn't settle out.

Way too complicated.

I even had the crazy idea for painting the resulting booster a garish color to look like a big crayon! (Inspiration for kids, and all...)  :)

On the other hand....if your looking for a new propellant why not use solid salami? Mythbusters proved it was possible to use salami as solid rocket fuel.....although there are drawbacks.....such as burnt salami smoke. :(

Pork as a rocket fuel?  Hmmmm...  Great way of getting rid of a few members of Congress....


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Offline strangequark

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Re: "Diesel" type rocket engine?
« Reply #27 on: 03/16/2010 06:43 pm »
Not to ruin a pretty good point, but Silane is a gas.  It pretty much matches the same molecular structure as Methane, but with silicon in place of Carbon.  Unlike Methane, though, Silane will automatically combust in the presence of Oxygen.  (Saves on the igniter costs)

Yes, and the sun rises in the east. I know that Silane is a gas (well, or liquid, in this application). My point, if you reread, is that when you burn silane with oxygen, you get silicon dioxide (better known as sand), and silicon monoxide (a glass). Thank you for the chemistry lesson, I am familiar with silane’s status as a methane analogue. Realize that methane produces carbon dioxide and carbon monoxide, which are substantially different from their silicon-based equivalents (specifically, they stay gases). The Isp values being quoted may not account for the severe losses incurred by having the exhaust be a two-phase flow of sandy steam. That would be why I asked Martin about it. Furthermore, the advantage that silane has over methane has nothing to do with “igniter costs”. There are plenty of easier hypergolic (the correct term for “automatically combusting”) combinations. Silane has appeal because it can be produced on the moon from readily available materials. The moon is carbon and nitrogen poor, which are the prime constituents to almost all traditional liquid fuels. Lastly, I know I’m being a little harsh, but understand that you just tried to explain basic chemistry to someone who is almost done with a Master’s degree in aerospace engineering (mind you, I’m an ignorant baby compared to many on this forum). A wise man once told me that if you want to appear foolish, try to tell an accountant how to add.

What I am saying is that we develop engines and rockets that can use a variety of fuels dependant upon the mission and ayload requirements.  By being able to mass produce a series of different scaled rockets that would have a range of payload masses to orbit, depending upon the fuels and oxidizers used.  By using a standardized rocket format, with fuel flexibility, it was my thinking that costs could be lowered by shear volume of production of the hardware.

To try to stay relevant, after my angry rant, the conversion process would not be as easy as you have indicated. Rocket engines balance a huge number of different elements to arrive at a design that works. You cannot readily pull out a given component and pop in another (Rockets are not legos). If you’re really interested in how these play together, there are some good books on the subject. Sutton’s “Rocket Propulsion Elements” is good as a first book.

Offline A_M_Swallow

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Re: "Diesel" type rocket engine?
« Reply #28 on: 03/16/2010 07:11 pm »
One thing to take into account when designing a new rocket engine, for the Moon, is the cost of the propellant.  On Earth the fuel costs less than 1% of the price of the LV, on the Moon the fuel will probably cost more than a reusable lander per landing.

Carbon and nitrogen on the Moon are estimated to cost more around $100,000 per kilogram, since they are not ISRU.  The cost of hydrogen is unknown but could be high.

Aluminium and iron will cost (cost of making ISRU machines + getting them to the Moon + operating cost +  repairs + materials from Earth) / mass refined

If the machines produce 10 times their mass before wearing out ISRU aluminium and iron are going to cost something like $10,000 to $40,000 per kilogram.

Offline JasonAW3

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Re: "Diesel" type rocket engine?
« Reply #29 on: 03/16/2010 08:36 pm »
Not to ruin a pretty good point, but Silane is a gas.  It pretty much matches the same molecular structure as Methane, but with silicon in place of Carbon.  Unlike Methane, though, Silane will automatically combust in the presence of Oxygen.  (Saves on the igniter costs)

Yes, and the sun rises in the east. I know that Silane is a gas (well, or liquid, in this application). My point, if you reread, is that when you burn silane with oxygen, you get silicon dioxide (better known as sand), and silicon monoxide (a glass). Thank you for the chemistry lesson, I am familiar with silane’s status as a methane analogue. Realize that methane produces carbon dioxide and carbon monoxide, which are substantially different from their silicon-based equivalents (specifically, they stay gases). The Isp values being quoted may not account for the severe losses incurred by having the exhaust be a two-phase flow of sandy steam. That would be why I asked Martin about it. Furthermore, the advantage that silane has over methane has nothing to do with “igniter costs”. There are plenty of easier hypergolic (the correct term for “automatically combusting”) combinations. Silane has appeal because it can be produced on the moon from readily available materials. The moon is carbon and nitrogen poor, which are the prime constituents to almost all traditional liquid fuels. Lastly, I know I’m being a little harsh, but understand that you just tried to explain basic chemistry to someone who is almost done with a Master’s degree in aerospace engineering (mind you, I’m an ignorant baby compared to many on this forum). A wise man once told me that if you want to appear foolish, try to tell an accountant how to add.

What I am saying is that we develop engines and rockets that can use a variety of fuels dependant upon the mission and ayload requirements.  By being able to mass produce a series of different scaled rockets that would have a range of payload masses to orbit, depending upon the fuels and oxidizers used.  By using a standardized rocket format, with fuel flexibility, it was my thinking that costs could be lowered by shear volume of production of the hardware.

To try to stay relevant, after my angry rant, the conversion process would not be as easy as you have indicated. Rocket engines balance a huge number of different elements to arrive at a design that works. You cannot readily pull out a given component and pop in another (Rockets are not legos). If you’re really interested in how these play together, there are some good books on the subject. Sutton’s “Rocket Propulsion Elements” is good as a first book.



Hmmm... Gee, so I should also look out for chunks of falling dry ice when a methane / LOX rocket launches as well?

     The Silicon Dioxide and Monoxide will remain a gas until it has a chance to cool down after leaving the exhaust.  Even then, it will be so spread out in a vacuum that it would not be able to clump up into sand.  The inner walls of the exhaust and combustion chamber will be too hot for it to do anything more than make a very temporary thin liquid coating of glass as it is revaporized into combustion gas.
     The only likely issue here would be a very small plug of glass forming over the injectors from the slight amount of risidual glass-gas remaining in the combustion chamber, which would be popped out as soon as the fuel and oxidizer were to be pressurized in the lines again.  As to the igniter, as thin as the glass coating would be, it would offer only marginal resistance before it too was blown away.

      As to the 'huge number of elements' I take it you're refereing to combustion chamber shapes, fuel  pressures, injector types, igniter types, fuel preheating, chamber and exhaust cooling, gymballing systems, gasket types, hose and piping types, monitoring sensors, valving systems, any variety of thermocouples, and so forth?
     Properly configured, it may be possible to swap out the needed components as a unit or series of units, while updating the needed control software with a thumbdrive to the appropriate avionics computer.
     Yes, I oversimplified the plumbing cabling and electronics issues, but I am trying to take the 'Off The Shelf' concept to it's logical conclusion.
     Maybe we SHOULD consider how we can make rocket motors that can be built like Legos.  Simple works.
     Yes, we'd need a variety of injectors, combustion chambers, etc.  But do we really NEED each engine to be built like an Italian Sports Car, or could we set up a system that produces Honda Car style rocket motors?  Yes, they SHOULD come in a variety of sizes, from small thrusters to big suckers maybe on the order of the old F-1 engine.  (Continuing the analogy, different horsepower motors for different jobs)  and maybe we should decide on a few different fuel / oxidizer mixes.  But do we REALLY need to have such a huge variety of engines that when you select one, it is almost custom built?

     Oh, to heck with it.  I figured lowering costs by standardizing motors and mass producing them was a good idea.  Obviously I was deeply mistaken.

Jason
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Offline 93143

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Re: "Diesel" type rocket engine?
« Reply #30 on: 03/16/2010 10:53 pm »
Jason, silicon dioxide condenses at 2230ºC at sea level.  If the pressure is higher, the boiling point goes up from there.

Now, you may not know this, but rocket exhaust cools as it transits the nozzle.  This is because the thermal energy that made it hot is being converted to bulk kinetic energy (that's what the nozzle is for, and it's why rockets work).

The question is, does the silicon dioxide condense and maybe even solidify (1650ºC) partway through the nozzle?  Because that kind of loss of expansion potential could harm Isp, not to mention possible nozzle damage from particulates.

I figured lowering costs by standardizing motors and mass producing them was a good idea.  Obviously I was deeply mistaken.

I don't know about that...  I believe the RL-10 has been fired on lots of different propellant combinations, not just LOX/LH2 and LOX/CH4.  And I don't think there was a turbomachinery swapout necessary to do it; it seems like a lot of effort to redesign the turbopumps just to run FLOX instead of LOX.  Also, it's been said that in true mass production the RL-10 could cost as little as $50,000 a pop.
« Last Edit: 03/16/2010 11:00 pm by 93143 »

Offline Jim

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Re: "Diesel" type rocket engine?
« Reply #31 on: 03/16/2010 11:00 pm »


      As to the 'huge number of elements' I take it you're refereing to combustion chamber shapes, fuel  pressures, injector types, igniter types, fuel preheating, chamber and exhaust cooling, gymballing systems, gasket types, hose and piping types, monitoring sensors, valving systems, any variety of thermocouples, and so forth?
     Properly configured, it may be possible to swap out the needed components as a unit or series of units, while updating the needed control software with a thumbdrive to the appropriate avionics computer.
     Yes, I oversimplified the plumbing cabling and electronics issues, but I am trying to take the 'Off The Shelf' concept to it's logical conclusion.
     Maybe we SHOULD consider how we can make rocket motors that can be built like Legos.  Simple works.
     Yes, we'd need a variety of injectors, combustion chambers, etc.  But do we really NEED each engine to be built like an Italian Sports Car, or could we set up a system that produces Honda Car style rocket motors?  Yes, they SHOULD come in a variety of sizes, from small thrusters to big suckers maybe on the order of the old F-1 engine.  (Continuing the analogy, different horsepower motors for different jobs)  and maybe we should decide on a few different fuel / oxidizer mixes.  But do we REALLY need to have such a huge variety of engines that when you select one, it is almost custom built?

     Oh, to heck with it.  I figured lowering costs by standardizing motors and mass producing them was a good idea.  Obviously I was deeply mistaken.


1.  Why?  Are jet engines and motor vehicle engines done this way?  No

2.  How many engines are needed per year?  Not enough even if was possible to make a swiss army knife engine. 

Offline mmeijeri

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Re: "Diesel" type rocket engine?
« Reply #32 on: 03/16/2010 11:03 pm »
I found an answer to some of the questions we've been discussing in this paper by the aforementioned Mr Hidding:

Spiking of Hydrocarbon Fuels with Silanes-based Combustion Enhancers

Production of liquid phase silicon oxides is indeed an issue with silanes. Blended propellants can indeed be useful for Isp, with proper blends being superior to either fuel in pure form. They are also useful for inducing hypergolicity and more generally improving combustion properties. Silanes are so reactive that they typically have somewhat better Isp than the corresponding alkanes, despite the higher molecular weight. This can be negated to a degree by two phase losses. Proper use of blends can solve this problem. Surprisingly, liquid phase silicon oxides are not all bad, they make for excellent film cooling and silanes have been added to hydrocarbon fuels precisely for that reason.

Most of the Isp numbers are purely theoretical, using thermodynamic databases, but the research described in this paper has been delving into quantum chemistry. Unsurprisingly the authors recommend further research into this fascinating subject. :)
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Offline JasonAW3

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Re: "Diesel" type rocket engine?
« Reply #33 on: 03/17/2010 12:50 am »

<Massive Kersnip>


1.  Why?  Are jet engines and motor vehicle engines done this way?  No

2.  How many engines are needed per year?  Not enough even if was possible to make a swiss army knife engine. 


1.  Actually, to a certain extent, some are.  Two different V-8 engines could share the same block and various other parts, but sufficent numbers of parts and computer programming differences for timing and control, make the two engines different beasts entirely.
     Between jet engines, There are a number of military aircraft that use the same engine between different types of craft, but are configured to the particular airframe that they are in. 
     In fact, as an example of craft commonality, the F-35 was designed with up to a 70% parts commonality with the F-22.  (At least originally.  This may have changed from the testing phase to the present).  Whether or not this was true of the F-35's engine to the F-22's, I don't really know, nor do I really want to, as this may be classified info.

2.  Right now, I have to agree with you.  And as Government run Human Space Flight space craft are about to go the way of the Dodo, and unless the HSF based corporations can step up to the plate, Human Space Flight itself for the US will go the way of the dinosaurs.
     The problem as I see it is the launch vehicle cost.
     If we had to throw away a 747 each time it was used, flight costs from New York to LA, then flying from coast to coast would cost about the same per kilogram as it does to get to Low Earth Orbit.
     The idea here is a low cost disposable system as an interim stage to development of a realistic low cost RLV system.
     I figured that we should look into ways of lowering the costs of the most expensive part of a rocket first, namely the engines, and then start working on the rest of the bird to find cheaper alternatives to accomplish the same mission for each part replaced.

     Maybe a clean slate approach would work better.  I don't know.  I'm just throwing ideas out here that seem reasonable, (With the exception of my infamous 3am ideas.  Sorry about those.  Lack of sleep can cause weird thoughts when you really know better) but may, for one reason or another, have a flaw I either didn't know about, or did not see at the time.   That's why I throw them out here for your feedback.

     If I put a bad idea out there, like anyone who is asking a question, I'd like to know what about the idea is bad.  and if it's a good idea, then I'd like to know that too, and maybe get a bit of credit for it as well.

     Sometimes, I'll put out what at first appears to be a bad idea, but in those cases, I may have insufficently explained the idea, (as with this one) and upon further explaination, it might not be a bad idea after all.  If something seems to need further explaination, ask!  I'll be happy to elaborate on my thoughts.  And if bad, I'll accept that, as long as someone would explain why it was a bad idea.

     In this case, a core motor that could run on a variety of pressurized, non-cryonic fuels through reconfiguration of appropriate feed systems, ignition systems, hydraulics and electronics, is not a good idea, as there isn't enough payloads going to orbit to justify the expense of developing the system.
     But in the same vein, we won't likely see an increase that would justify such expendatures UNTIL we have a cheaper launch capibility.  So, we're caught in a Catch 22 situation.

     Well, I guess I'll just keep on thinking.  maybe I'll come up with something useful...

Jason
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Offline Jim

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Re: "Diesel" type rocket engine?
« Reply #34 on: 03/17/2010 02:01 am »


1.  Actually, to a certain extent, some are.  Two different V-8 engines could share the same block and various other parts, but sufficent numbers of parts and computer programming differences for timing and control, make the two engines different beasts entirely.
     Between jet engines, There are a number of military aircraft that use the same engine between different types of craft, but are configured to the particular airframe that they are in. 
     In fact, as an example of craft commonality, the F-35 was designed with up to a 70% parts commonality with the F-22.  (At least originally.  This may have changed from the testing phase to the present).  Whether or not this was true of the F-35's engine to the F-22's, I don't really know, nor do I really want to, as this may be classified info.

2.  Right now, I have to agree with you.  And as Government run Human Space Flight space craft are about to go the way of the Dodo, and unless the HSF based corporations can step up to the plate, Human Space Flight itself for the US will go the way of the dinosaurs.
 
3,      The problem as I see it is the launch vehicle cost.
     If we had to throw away a 747 each time it was used, flight costs from New York to LA, then flying from coast to coast would cost about the same per kilogram as it does to get to Low Earth Orbit.
     The idea here is a low cost disposable system as an interim stage to development of a realistic low cost RLV system.
 
4.    I figured that we should look into ways of lowering the costs of the most expensive part of a rocket first, namely the engines, and then start working on the rest of the bird to find cheaper alternatives to accomplish the same mission for each part replaced.

5.      Maybe a clean slate approach would work better.  I don't know.  I'm just throwing ideas out here that seem reasonable, (With the exception of my infamous 3am ideas.  Sorry about those.  Lack of sleep can cause weird thoughts when you really know better) but may, for one reason or another, have a flaw I either didn't know about, or did not see at the time.   That's why I throw them out here for your feedback.



1.  And all those mods are done in the factory and are optimized.  They are not sacrificing performance for interchangeability.   Your jet engine example is not valid.  The engines use the same core and same fuel.  Accessories and structural adaptions are not the same as changing propellant in a rocket engine.  Rocket engines do the same thing as you mention, look at the RL10B-2 and RL10A-4-2.  The core is the same.

2.  No, Gov't run HSF is not the same as US HSF.  ULA, Spacex, SpaceDev and others are working HSF.

3.  RLV don't come into effect until flight rates of 30-50 per year.

4.  Reducing ISP isn't going to get your there.

5. Rocket science is rocket science, it isn't going to change (for chemical rockets).  The issue is labor.




Offline Rabidpanda

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Re: "Diesel" type rocket engine?
« Reply #35 on: 03/17/2010 02:04 am »

     If I put a bad idea out there, like anyone who is asking a question, I'd like to know what about the idea is bad.  and if it's a good idea, then I'd like to know that too, and maybe get a bit of credit for it as well.

     Sometimes, I'll put out what at first appears to be a bad idea, but in those cases, I may have insufficently explained the idea, (as with this one) and upon further explaination, it might not be a bad idea after all.  If something seems to need further explaination, ask!  I'll be happy to elaborate on my thoughts.  And if bad, I'll accept that, as long as someone would explain why it was a bad idea.

     In this case, a core motor that could run on a variety of pressurized, non-cryonic fuels through reconfiguration of appropriate feed systems, ignition systems, hydraulics and electronics, is not a good idea, as there isn't enough payloads going to orbit to justify the expense of developing the system.
     But in the same vein, we won't likely see an increase that would justify such expendatures UNTIL we have a cheaper launch capibility.  So, we're caught in a Catch 22 situation.

     Well, I guess I'll just keep on thinking.  maybe I'll come up with something useful...

Jason

Creativity is definetly a good thing and you seem to generate a lot of ideas, however, if I were you, I wouldn't immediately post new ideas onto this forum.  Refine it in your head, research it, crunch some numbers, and after all that if it still seems practical and viable THEN post it here.  That's my advice.

Offline JasonAW3

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Re: "Diesel" type rocket engine?
« Reply #36 on: 03/17/2010 03:38 am »


1.  Actually, to a certain extent, some are.  Two different V-8 engines could share the same block and various other parts, but sufficent numbers of parts and computer programming differences for timing and control, make the two engines different beasts entirely.
     Between jet engines, There are a number of military aircraft that use the same engine between different types of craft, but are configured to the particular airframe that they are in. 
     In fact, as an example of craft commonality, the F-35 was designed with up to a 70% parts commonality with the F-22.  (At least originally.  This may have changed from the testing phase to the present).  Whether or not this was true of the F-35's engine to the F-22's, I don't really know, nor do I really want to, as this may be classified info.

2.  Right now, I have to agree with you.  And as Government run Human Space Flight space craft are about to go the way of the Dodo, and unless the HSF based corporations can step up to the plate, Human Space Flight itself for the US will go the way of the dinosaurs.
 
3,      The problem as I see it is the launch vehicle cost.
     If we had to throw away a 747 each time it was used, flight costs from New York to LA, then flying from coast to coast would cost about the same per kilogram as it does to get to Low Earth Orbit.
     The idea here is a low cost disposable system as an interim stage to development of a realistic low cost RLV system.
 
4.    I figured that we should look into ways of lowering the costs of the most expensive part of a rocket first, namely the engines, and then start working on the rest of the bird to find cheaper alternatives to accomplish the same mission for each part replaced.

5.      Maybe a clean slate approach would work better.  I don't know.  I'm just throwing ideas out here that seem reasonable, (With the exception of my infamous 3am ideas.  Sorry about those.  Lack of sleep can cause weird thoughts when you really know better) but may, for one reason or another, have a flaw I either didn't know about, or did not see at the time.   That's why I throw them out here for your feedback.



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1.  And all those mods are done in the factory and are optimized.  They are not sacrificing performance for interchangeability.   Your jet engine example is not valid.  The engines use the same core and same fuel.  Accessories and structural adaptions are not the same as changing propellant in a rocket engine.  Rocket engines do the same thing as you mention, look at the RL10B-2 and RL10A-4-2.  The core is the same.


     So, essentially, there already IS a motor that set up in this fashion as stated.  Ok!  But a conversion kit isn't possible?  Isn't that kind of what they did to the RL-10 Core unit?  And based upon this technology couldn't we build bigger or smaller core units like this one?   If so, would there be an advantage to this?

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2.  No, Gov't run HSF is not the same as US HSF.  ULA, Spacex, SpaceDev and others are working HSF.


     Ok, I stand corrected.  So the pilots and scientists are contractors from these companies?  I didn't think this would happen until after shuttle retirement.  Or the Obama NASA Budget is approved.

     And, while I'm sure that there would be a heck of a bonus from the company, I'm not at all positive that any company pilots, maintenance crew, doctors, etc. are going to be willing to spend upwards of two to three years on an untried spacecraft going to Mars, nor even three or four days going to and coming from the moon.  Insurance companies would freak at the potentile costs if the mission is a catastrophic failure.
     As much as respect Elon Musk and company, I seriously doubt that they are going to put up that much equipment with that kind of value, let alone the people, without some sort of HUGE monitary compensation deposited in a bank, in advance incase the worst happens.
     Until this issue is addr4essed, we're going to be stuck in LEO for the forseeable future.

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3.  RLV don't come into effect until flight rates of 30-50 per year.


     Ok, I accept that. but until then, shouldn't we try to develope the cheapest, safest, disposable rockets we can in the meantime?

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4.  Reducing ISP isn't going to get your there.


     Ok, I'll take that as a given.  So could other motors be multioptimized like the RL-10?  If so, is there enough of an advantage to actively pursue?

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5. Rocket science is rocket science, it isn't going to change (for chemical rockets).  The issue is labor.


     Ok, you kind of lost me on this one.  By labor, are we talking about the crew needed to launch a rocket or what?  Or are we talking about the labor on the motors themselves?
     Obviously lowering labor costs should be a prime concern, but I'm not sure if that's what you're talking about here.  Could you elaborate?

Jason
My God!  It's full of universes!

Offline jimgagnon

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Re: "Diesel" type rocket engine?
« Reply #37 on: 03/17/2010 05:13 am »
Production of liquid phase silicon oxides is indeed an issue with silanes. Blended propellants can indeed be useful for Isp, with proper blends being superior to either fuel in pure form. They are also useful for inducing hypergolicity and more generally improving combustion properties. Silanes are so reactive that they typically have somewhat better Isp than the corresponding alkanes, despite the higher molecular weight. This can be negated to a degree by two phase losses. Proper use of blends can solve this problem. Surprisingly, liquid phase silicon oxides are not all bad, they make for excellent film cooling and silanes have been added to hydrocarbon fuels precisely for that reason.

Interesting, though Hidding doesn't address the nozzle caking issue. Also, he doesn't mention silane's toxicity: it's poisonous at 1% concentration in atmosphere.

The planetary ISRU guys like silane and diborane as they burn in a carbon dioxide atmosphere. Not sure if the Martian atmosphere is dense enough to support a silane jet, but Venus certainly is -- if you can solve that pesky caking issue.

Offline mmeijeri

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Re: "Diesel" type rocket engine?
« Reply #38 on: 03/17/2010 10:36 am »
Interesting, though Hidding doesn't address the nozzle caking issue. Also, he doesn't mention silane's toxicity: it's poisonous at 1% concentration in atmosphere.

Supposedly it's less toxic than MMH/NTO and of course most fuels are toxic to some degree. Higher silanes are supposed to be less toxic, or at least they remain liquid.

I've read it before but I don't really understand how silane could be toxic in air. It's hypergolic with oxygen after all. Wouldn't you worry more about it being a fire hazard?
« Last Edit: 03/17/2010 07:12 pm by mmeijeri »
Pro-tip: you don't have to be a jerk if someone doesn't agree with your theories

Offline mmeijeri

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Re: "Diesel" type rocket engine?
« Reply #39 on: 03/17/2010 12:22 pm »
According to the Linde Gas MATERIAL SAFETY DATA SHEET silane does not spontaneously combust in air if concentrations are below roughly 1%.
Pro-tip: you don't have to be a jerk if someone doesn't agree with your theories

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