OTOH, it may be super important that feedback not be lost by segregation. Both can work of course. Hope they succeed. 30 employees is more than SpaceX had when SpaceX had ten times the money. But he seems to have identified a good market when having less seed money… will they have enough?
But really, since they had two shuttles with life support for four but nine people and screwing with other ships navigation is what saved them… shouldn’t they all have just stayed with Serenity for a higher probability of survival?
In other words, good name. Like: Hummingboard.
I think he is wrong. When you do them as separate processes you lose feedback from the operational side into the research side and the vehicle ends up being more expensive overall. Their propulsion choice also seems overly complex to me.
As for going into the small sat business SpaceX also thought about targeting that as a first approach then changed their business model once they realized they simply did not have enough sustained commercial activity for it to be viable. Plus I think they are scaling up too fast and they will probably run out of cash before actually launching anything at all. Elon bet his own fortune in SpaceX and nearly went bankrupt in the process. I do not know who these people’s financials backers are.
Then there is the little matter that they are outsourcing one of the most critical parts to an outside contractor. I think this will lead to nowhere. But I wish they succeed.
Did not see a line in there about making his carbon composite rockets reusable. He mentioned man flight toward the end and touched on reusable craft/capsule for carrying the people, but not a word about making his launching rockets themselves reusable, unless I missed it.
With a rocket this small, I doubt there’s enough margin to allow for reusability. Let them develop their current design, gain experience, and let things evolve naturally. They have enough challenges getting this design built without adding reusability to the list right now.
I’ve always wondered why you couldn’t make the bottom of a bell nozzle louvered.
Louvered as in entending or controled flow seperation rings?
Extending makes for a compact system until deployed, but has complexity and weight.
Controled flow seperation is tricky to get right, and won’t deliver the same vacuum performance.
The Germans tried that during the V-2 program, but eventually abandoned it due to a problem I would have thought easily foreseeable. They were using 75% ethyl alcohol as fuel, which of course always resulted in cirrhosis of the louver.
Rand should ban you for that horrible pun. 😉
What I’m imagining is a vacuum nozzle on the pad at sea-level pressure, but with part of the bottom of the nozzle divided into slats, like louvers, that can be opened slightly so their section of the nozzle wall is vertical and open at the top, admitting in external air or just passing it along in flight, as if that section of the nozzle didn’t exist aerodynamically, other than perhaps some shock wave effects as the vehicle goes supersonic, but by then they’re mostly closing anyway.
Another way to think of it is that the vertical stringers or frame for a vacuum nozzle is in place on the pad, but the bottom wall of the nozzle is not. That’s added row by row to match the external pressure. The louver idea is just a way to simply achieve the affect, eliminating the back flow from low-altitude over expansion by sucking the air that’s traveling past the outside of the lower part of the nozzle and moving it directly to the inside. Some jet engine nozzles have used something similar, pulling extra outside air through a series of slats just prior to the nozzle exit, instead of using a complicated adjustable exit area.
This idea has already been patented though I would also like to see it be tried:
Well, at least I still have the corner on the high-volume, high-pressure propellant pump with no moving parts. 🙂 I should try to cobble something together for a test of the concept, but to do so I really need a small liquid fueled thruster – which I don’t have.
I do have a related question that I can’t answer. I came up with the idea of cooling a combustion chamber by making the wall out of rollers, then having a sheet of stainless steel foil thread around all the rollers and out into the surrounding cooling jacket, allowing for enormous heat fluxes while only warming the foil to a few hundred degrees (based on transient heat transfer code). The foil only has to move at 10 to 15 mph to accomplish this if the rollers are small (1/2″ or so). There are some complexities like sealing the edge of the foil, keeping it tracked (so it doesn’t drift), and tapered roller sections to complete the required geometry, but it looks potentially workable and dirt dirt cheap to make. SSME performance for the price of a car.
But while I was going over all sorts of geometric designs, it seemed the easiest way to make a throat was to lay the rollers sideways and have the the ones tapering toward the throat, and after, laying horizontally. The entire combustion chamber could be similar, with two tapered-roller sections on each side, along with a variety of clever injectors, from pintles to perforated foil (and underlying perforated rollers). A linear, slit-like throat is trivially adjustable, as is the exit area, because the design is 2-D.
Then it occurred to me that the skin friction in the throat could drive the foil around, and the foil could drive the rollers, which are all geared together, so I don’t even need a power source to spin the rollers, they’re powered by the thrust. And then I saw something that still bugs me. In a de Laval nozzle, the exhaust at the throat is exactly Mach 1 – relative to the throat, as the rocket itself is also moving at some given velocity. But in my design the surface skin of the throat could be moving at a hundred mph or more. Does that velocity add in, so that the Mach 1 shock wave is relative to the high-velocity surface and not the geometrically constant narrowest point, or does the shock wave have to be where the gas transitions from contraction to expansion? It’s one of those blank spots in my education. I suppose I could aim an air jet between two free-spinning rollers and get an answer, or I could figure that somebody here already knows.
Obviously this comment means I’m going with the latter.
From what I understand the concept seems workable. You should at least get a provisional patent to protect the concept.
A big portion of the cost of a rocket engine comes from the turbopumps and all the associated machinery. The cooling systems are a smaller component of the costs. So your engines could still be expensive. However, for rocket engines a major concern is weight. If your methods could reduce the weight a significant percentage that would be important.
Note once you get a least a provisional patent you could shop around for private and government funding to develop it. The nice thing about your idea is that rather than having to test it on a full fledge engine you could test the cooling properties simply by flowing heated gas or liquid through it. This should make it much cheaper to do a proof of concept test.
Bob Clark
That sounds like a good idea, and the pump is a much simpler concept than the engine (which was dreamed up as a simple way to make a thruster – just to test the pump), but I’d still want to run a couple pump experiments to make sure it’s not off in crazy land.
A pump with no moving parts, and a combustion chamber with hundreds of precision tolerance moving parts…
I would like to see how the pump is supposed to work.
I’m reluctant to talk about the pump openly. It’s one of those maddening things where I’m either crazy or everyone else is blind.
But, if you did aim rocket exhaust upward and sprayed a bunch of fire hoses at it, the water would get blasted high into the air, perhaps landing in a barrel on a high hill. If you ran a pipe from the barrel back down to the engine, the flow out the bottom would be the same as the flow coming out of the 60 psi fire hoses, but at an extremely high pressure head. Then you just eliminate the hill.
The thermodynamics look good and by default it acts like a staged combustion cycle, with I think roughly comparable efficiencies.
How would that interact with the TVC? (It isn’t mentioned in the article, but I assume they are using TVC; I also don’t know if there are any potential TVC interactions with the aerospike engine.) in general I was disappointed that there was no discussion of G&C, but since that’s my field, I would have that take wouldn’t I? 🙂
I like a lot of that, but I have to predict failure because they are trying to execute multiple significant technological innovations simultaneously; IMAO this is almost always a predictor of failure.
If composite pressurized bodies are a Big Win, do that first with conventional engines.
If small-scale aerospikes are a Bigger Win, do that first with conventional tanks.
Doing both at once means you have two points of failure, and if by chance you do succeed it isn’t necessarily much better than if you tried to do them serially.
The fact that this is an engineer-led company, and the complaints about production interfering with R&D, only reinforce my suspicion that they will run out of money before producing the wonderful perfect thing.
I agree completely. The technological aggressiveness reminds me a bit of some of the NASA SSTO projects. All the innovations have to pan out or they don’t have a working vehicle, and without a working vehicle they can’t test fly any of the innovations. But perhaps they also have some incremental testing plans in the works.
That is true about needing both advanced techs to pan out for it to work. Fortunately, for both the aerospikes and the composite tanks there is work involving actually developed and tested systems going back decades.
Also, about the composite tanks people are wary about them because of the experience with X-33 where they failed. Keep in mind though that was due to their unusual conformal shape. Cylindrical tanks made of composites are now well characterized.
Bob Clark
The X-33 had the most problems with the LH2 composite tank. AFAIK the build a LOX tank just fine.
I agree with your assertion. I heard it from Seymour Cray first though. You should never try more than one new tech at once.
[Tom http://www.spacenews.com/article/features/42177profile-thomas-markusic-founder-and-chief-executive-firefly-space-systems thinks] it’s super important to decouple what’s going on in R&D from production. I think that’s a mistake we made at SpaceX. You have the current generation and the next generation of vehicles stepping on each other’s toes in the same facility.
OTOH, it may be super important that feedback not be lost by segregation. Both can work of course. Hope they succeed. 30 employees is more than SpaceX had when SpaceX had ten times the money. But he seems to have identified a good market when having less seed money… will they have enough?
But really, since they had two shuttles with life support for four but nine people and screwing with other ships navigation is what saved them… shouldn’t they all have just stayed with Serenity for a higher probability of survival?
In other words, good name. Like: Hummingboard.
I think he is wrong. When you do them as separate processes you lose feedback from the operational side into the research side and the vehicle ends up being more expensive overall. Their propulsion choice also seems overly complex to me.
As for going into the small sat business SpaceX also thought about targeting that as a first approach then changed their business model once they realized they simply did not have enough sustained commercial activity for it to be viable. Plus I think they are scaling up too fast and they will probably run out of cash before actually launching anything at all. Elon bet his own fortune in SpaceX and nearly went bankrupt in the process. I do not know who these people’s financials backers are.
Then there is the little matter that they are outsourcing one of the most critical parts to an outside contractor. I think this will lead to nowhere. But I wish they succeed.
Did not see a line in there about making his carbon composite rockets reusable. He mentioned man flight toward the end and touched on reusable craft/capsule for carrying the people, but not a word about making his launching rockets themselves reusable, unless I missed it.
With a rocket this small, I doubt there’s enough margin to allow for reusability. Let them develop their current design, gain experience, and let things evolve naturally. They have enough challenges getting this design built without adding reusability to the list right now.
I’ve always wondered why you couldn’t make the bottom of a bell nozzle louvered.
Louvered as in entending or controled flow seperation rings?
Extending makes for a compact system until deployed, but has complexity and weight.
Controled flow seperation is tricky to get right, and won’t deliver the same vacuum performance.
The Germans tried that during the V-2 program, but eventually abandoned it due to a problem I would have thought easily foreseeable. They were using 75% ethyl alcohol as fuel, which of course always resulted in cirrhosis of the louver.
Rand should ban you for that horrible pun. 😉
What I’m imagining is a vacuum nozzle on the pad at sea-level pressure, but with part of the bottom of the nozzle divided into slats, like louvers, that can be opened slightly so their section of the nozzle wall is vertical and open at the top, admitting in external air or just passing it along in flight, as if that section of the nozzle didn’t exist aerodynamically, other than perhaps some shock wave effects as the vehicle goes supersonic, but by then they’re mostly closing anyway.
Another way to think of it is that the vertical stringers or frame for a vacuum nozzle is in place on the pad, but the bottom wall of the nozzle is not. That’s added row by row to match the external pressure. The louver idea is just a way to simply achieve the affect, eliminating the back flow from low-altitude over expansion by sucking the air that’s traveling past the outside of the lower part of the nozzle and moving it directly to the inside. Some jet engine nozzles have used something similar, pulling extra outside air through a series of slats just prior to the nozzle exit, instead of using a complicated adjustable exit area.
This idea has already been patented though I would also like to see it be tried:
Rocket motor thrust nozzle with means to direct atmospheric air into the interior of the nozzle.
US 3469787 A.
https://www.google.com/patents/US3469787
Bob Clark
Well, at least I still have the corner on the high-volume, high-pressure propellant pump with no moving parts. 🙂 I should try to cobble something together for a test of the concept, but to do so I really need a small liquid fueled thruster – which I don’t have.
I do have a related question that I can’t answer. I came up with the idea of cooling a combustion chamber by making the wall out of rollers, then having a sheet of stainless steel foil thread around all the rollers and out into the surrounding cooling jacket, allowing for enormous heat fluxes while only warming the foil to a few hundred degrees (based on transient heat transfer code). The foil only has to move at 10 to 15 mph to accomplish this if the rollers are small (1/2″ or so). There are some complexities like sealing the edge of the foil, keeping it tracked (so it doesn’t drift), and tapered roller sections to complete the required geometry, but it looks potentially workable and dirt dirt cheap to make. SSME performance for the price of a car.
But while I was going over all sorts of geometric designs, it seemed the easiest way to make a throat was to lay the rollers sideways and have the the ones tapering toward the throat, and after, laying horizontally. The entire combustion chamber could be similar, with two tapered-roller sections on each side, along with a variety of clever injectors, from pintles to perforated foil (and underlying perforated rollers). A linear, slit-like throat is trivially adjustable, as is the exit area, because the design is 2-D.
Then it occurred to me that the skin friction in the throat could drive the foil around, and the foil could drive the rollers, which are all geared together, so I don’t even need a power source to spin the rollers, they’re powered by the thrust. And then I saw something that still bugs me. In a de Laval nozzle, the exhaust at the throat is exactly Mach 1 – relative to the throat, as the rocket itself is also moving at some given velocity. But in my design the surface skin of the throat could be moving at a hundred mph or more. Does that velocity add in, so that the Mach 1 shock wave is relative to the high-velocity surface and not the geometrically constant narrowest point, or does the shock wave have to be where the gas transitions from contraction to expansion? It’s one of those blank spots in my education. I suppose I could aim an air jet between two free-spinning rollers and get an answer, or I could figure that somebody here already knows.
Obviously this comment means I’m going with the latter.
From what I understand the concept seems workable. You should at least get a provisional patent to protect the concept.
A big portion of the cost of a rocket engine comes from the turbopumps and all the associated machinery. The cooling systems are a smaller component of the costs. So your engines could still be expensive. However, for rocket engines a major concern is weight. If your methods could reduce the weight a significant percentage that would be important.
Note once you get a least a provisional patent you could shop around for private and government funding to develop it. The nice thing about your idea is that rather than having to test it on a full fledge engine you could test the cooling properties simply by flowing heated gas or liquid through it. This should make it much cheaper to do a proof of concept test.
Bob Clark
That sounds like a good idea, and the pump is a much simpler concept than the engine (which was dreamed up as a simple way to make a thruster – just to test the pump), but I’d still want to run a couple pump experiments to make sure it’s not off in crazy land.
A pump with no moving parts, and a combustion chamber with hundreds of precision tolerance moving parts…
I would like to see how the pump is supposed to work.
I’m reluctant to talk about the pump openly. It’s one of those maddening things where I’m either crazy or everyone else is blind.
But, if you did aim rocket exhaust upward and sprayed a bunch of fire hoses at it, the water would get blasted high into the air, perhaps landing in a barrel on a high hill. If you ran a pipe from the barrel back down to the engine, the flow out the bottom would be the same as the flow coming out of the 60 psi fire hoses, but at an extremely high pressure head. Then you just eliminate the hill.
The thermodynamics look good and by default it acts like a staged combustion cycle, with I think roughly comparable efficiencies.
How would that interact with the TVC? (It isn’t mentioned in the article, but I assume they are using TVC; I also don’t know if there are any potential TVC interactions with the aerospike engine.) in general I was disappointed that there was no discussion of G&C, but since that’s my field, I would have that take wouldn’t I? 🙂
I like a lot of that, but I have to predict failure because they are trying to execute multiple significant technological innovations simultaneously; IMAO this is almost always a predictor of failure.
If composite pressurized bodies are a Big Win, do that first with conventional engines.
If small-scale aerospikes are a Bigger Win, do that first with conventional tanks.
Doing both at once means you have two points of failure, and if by chance you do succeed it isn’t necessarily much better than if you tried to do them serially.
The fact that this is an engineer-led company, and the complaints about production interfering with R&D, only reinforce my suspicion that they will run out of money before producing the wonderful perfect thing.
I agree completely. The technological aggressiveness reminds me a bit of some of the NASA SSTO projects. All the innovations have to pan out or they don’t have a working vehicle, and without a working vehicle they can’t test fly any of the innovations. But perhaps they also have some incremental testing plans in the works.
That is true about needing both advanced techs to pan out for it to work. Fortunately, for both the aerospikes and the composite tanks there is work involving actually developed and tested systems going back decades.
Also, about the composite tanks people are wary about them because of the experience with X-33 where they failed. Keep in mind though that was due to their unusual conformal shape. Cylindrical tanks made of composites are now well characterized.
Bob Clark
The X-33 had the most problems with the LH2 composite tank. AFAIK the build a LOX tank just fine.
I agree with your assertion. I heard it from Seymour Cray first though. You should never try more than one new tech at once.