Falcon-9 is a 2-stage system with staging at about 10,000 fps. They want to recover and re-use the first stage. The second stage is an acknowledged throwaway. Their price is enough to cover operations without recovering the first stage.
I have my doubts about reusability with a 10% inert mass fraction on that first stage, but they might be able to salvage the engines a lot of the time. My guess is the tankage gets bent the majority of the time, even if the chute system is perfect. Lightweight is just fragile, no two ways around that.
TPS is an issue needing some better solutions than we have seen. One is lower wing loading / ballistic coefficient, which puts more deceleration higher up in thinner air. From what I hear, peak temperatures are lower, although total integrated heat transferred is in fact higher. It's the peak temperatures that are driving the materials problems. From what I see posted, Skylon is moving toward lower wing loadings.
The solution to the shuttle tile problem is flexible blankets of woven fiber material, or else a ceramic composite material. The blanket might simplify to nothing more than a ceramic fabric covering over a tube frame structure (like the old Piper Cub), if the lower wing loading lowers peak temperatures enough. I would kind of guess that fuselage and surface panels could be done this way, while leading edges and nose caps might require much tougher refractories, or even ablatives like carbon-carbon composite.
You might even get by with some alloy metal surfaces that are cooled with one-way sacrificial water blown into the wake as escaping steam. This was apparently one of the TPS schemes that was supposed to have been tested on the old cancelled X-20 long ago. Never was tested. Should be. Might be good.
The Next Generation of Human Spaceflight
-
GW Johnson
- Posts: 85
- Joined: Sat Sep 11, 2010 9:14 pm
- Location: McGregor, TX USA
- Contact:
-
GIThruster
- Posts: 4686
- Joined: Tue May 25, 2010 8:17 pm
It's as light as it is because it's carbon fiber. It may break but it's not going to bend.GW Johnson wrote:Falcon-9 is a 2-stage system with staging at about 10,000 fps. They want to recover and re-use the first stage. The second stage is an acknowledged throwaway. Their price is enough to cover operations without recovering the first stage.
I have my doubts about reusability with a 10% inert mass fraction on that first stage, but they might be able to salvage the engines a lot of the time. My guess is the tankage gets bent the majority of the time, even if the chute system is perfect. Lightweight is just fragile, no two ways around that.
Both stages are intended to be recovered and reused:
Although the stages are expendable for the initial launches, by flight six the first stage is intended to be recovered.[9] Although reusability of the second stage is more difficult, SpaceX has intended both stages of the Falcon 9 to be reusable.[11] Musk stated:
"By flight six we think it’s highly likely we’ll recover the first stage, and when we get it back we’ll see what survived through re-entry, and what got fried, and carry on with the process. ... That's just to make the first stage reusable, it'll be even harder with the second stage – which has got to have a full heatshield, it'll have to have deorbit propulsion and communication."[9]
Both stages are covered with a layer of ablative cork, have parachutes to land them gently in the sea and have been marinised by using salt water resistant materials, anodizing and paying attention to the issue of galvanic corrosion.[11]
While many commentators are skeptical of the viability of reusability, Musk has stated that reusability is one of the most important goals, and that if the vehicle does not become reusable, "I will consider us to have failed.”[12]
from: http://en.wikipedia.org/wiki/Falcon_9
"Courage is not just a virtue, but the form of every virtue at the testing point." C. S. Lewis
-
GW Johnson
- Posts: 85
- Joined: Sat Sep 11, 2010 9:14 pm
- Location: McGregor, TX USA
- Contact:
Interesting. I still think reentries closer downrange from only Mach 10 will be a lot more survivable than full de-orbits. But I guess it could be done. Won't be easy. Composites are very vulnerable to impact-induced hidden damage, by the way. Also very vulnerable to heat, far more so even than aluminum.
GW Johnson
McGregor, Texas
McGregor, Texas
-
GIThruster
- Posts: 4686
- Joined: Tue May 25, 2010 8:17 pm
Yes, it will be very instructive to see whether he can indeed reuse even the lower stage. I've thought for a long time that wet filament wound composites would be perfect for durable deep space craft. I think we'll find out the first time Musk deorbits a second stage just how durable the stuff is.
"Courage is not just a virtue, but the form of every virtue at the testing point." C. S. Lewis
Interesting tidbits about hypersonic aerodynamics: Re-Entry Aerodynamics
-
GW Johnson
- Posts: 85
- Joined: Sat Sep 11, 2010 9:14 pm
- Location: McGregor, TX USA
- Contact:
Are the Falcon 9 tanks full composite or are they hybrid metal plus composite? It's been a while since I looked on their site. For some reason, I thought aluminum was involved. I am pretty sure the skirts between the stages are composite.
Either way, the structure has to survive aeroheating, chute opening loads, water impact (which is about like hitting concrete at speeds over about 40 mph, as any water skier knows), and saltwater immersion. That's a tall order.
My own "take" on first stage reusability is a little different. I tend to favor stowed wings for flyback to a land landing. Perfect for strapons and members of a cluster. Big model airplane problem.
I also do tend to favor the higher inert weights that have traditionally conferred survivability and long service life in flying vehicles. For example, the most reusable rocket vehicle in history was the X-15, at 40% inert weight fraction.
Either way, the structure has to survive aeroheating, chute opening loads, water impact (which is about like hitting concrete at speeds over about 40 mph, as any water skier knows), and saltwater immersion. That's a tall order.
My own "take" on first stage reusability is a little different. I tend to favor stowed wings for flyback to a land landing. Perfect for strapons and members of a cluster. Big model airplane problem.
I also do tend to favor the higher inert weights that have traditionally conferred survivability and long service life in flying vehicles. For example, the most reusable rocket vehicle in history was the X-15, at 40% inert weight fraction.
GW Johnson
McGregor, Texas
McGregor, Texas
NASA Ames’ Worden reveals DARPA-funded ‘Hundred Year Starship’ program
http://www.kurzweilai.net/nasa-ames-wor ... um=twitter
“The microwave thermal thruster using beamed propulsion is an excellent idea,” said Dr. Narayanan M. Komerath, a professor at Georgia Tech College of Engineering and a NASA Institute of Advanced Concepts Fellow. “[Kevin Parker] picks the 140 GHz window, which apparently offers strong advantages in absorption by the materials that he uses in the propulsion system.”
http://www.kurzweilai.net/nasa-ames-wor ... um=twitter
-
GIThruster
- Posts: 4686
- Joined: Tue May 25, 2010 8:17 pm
Same double-talk we've been seeing for years.
"The idea is if you can beam power to the spaceship, so you don’t have to carry all the fuel; and then you use that energy from a laser or microwave power to heat a propellant; it gets you a pretty big factor of improvement."
No. It doesn't get you any improvement. You use the energy beamed from Earth to energize the propellant, but you don't have substantial gains over using a propellant that oxidizes and provides it's own exothermal energy. You might not need a heavy turbo-pump, but you need to collect the energy instead, and now you're tied to those trajectories possible with your microwave beaming stations on earth, and you have not less, but far more infrastructure which is where all the real expense is--not in the cost of propellant!
It just kills me that stupid ideas like this get funding while legitimate answers to our transportation needs do not. It all has to do with position inside NASA.
Worden should have remained fired.
"The idea is if you can beam power to the spaceship, so you don’t have to carry all the fuel; and then you use that energy from a laser or microwave power to heat a propellant; it gets you a pretty big factor of improvement."
No. It doesn't get you any improvement. You use the energy beamed from Earth to energize the propellant, but you don't have substantial gains over using a propellant that oxidizes and provides it's own exothermal energy. You might not need a heavy turbo-pump, but you need to collect the energy instead, and now you're tied to those trajectories possible with your microwave beaming stations on earth, and you have not less, but far more infrastructure which is where all the real expense is--not in the cost of propellant!
It just kills me that stupid ideas like this get funding while legitimate answers to our transportation needs do not. It all has to do with position inside NASA.
Worden should have remained fired.
"Courage is not just a virtue, but the form of every virtue at the testing point." C. S. Lewis
You remind me of Jeffery Bell. He would come out with a critique of what Nasa was doing, and in just a few sentences utterly destroy their idea(s).GIThruster wrote:Same double-talk we've been seeing for years.
"The idea is if you can beam power to the spaceship, so you don’t have to carry all the fuel; and then you use that energy from a laser or microwave power to heat a propellant; it gets you a pretty big factor of improvement."
No. It doesn't get you any improvement. You use the energy beamed from Earth to energize the propellant, but you don't have substantial gains over using a propellant that oxidizes and provides it's own exothermal energy. You might not need a heavy turbo-pump, but you need to collect the energy instead, and now you're tied to those trajectories possible with your microwave beaming stations on earth, and you have not less, but far more infrastructure which is where all the real expense is--not in the cost of propellant!
It just kills me that stupid ideas like this get funding while legitimate answers to our transportation needs do not. It all has to do with position inside NASA.
Worden should have remained fired.
I was going to ask your opinion of the Flowmetrics pistonless Turbo Pump replacement, but Flowmetrics appears to have killed all references to it. I suppose that means they discovered why it wasn't practical.
This is where it used to be.
http://www.flometrics.com/rockets/rocke ... etpump.htm
Are you familiar with it and do you have any commentary regarding it?
-
GW Johnson
- Posts: 85
- Joined: Sat Sep 11, 2010 9:14 pm
- Location: McGregor, TX USA
- Contact:
Beamed propulsion: It really is hard to beat plain old rocketry, isn't it?
Pumps for liquid propellants: link didn't work. Turbopumps are a pretty mature technology. Xcor Aerospace has a positive displacement pump driven by a waste heat engine for their still-small engines. New rearrangement of some very old technologies, but it seems to work fine for them. I've seen it. Very simple, very robust.
Other types of rockets: High pressure tankage that also serves as primary airframe structure is a very good fit with either solid rockets or hybrid rockets, or even simple pressure-fed liquids. Not as structurally efficient, to be sure, but a very tough design approach that is very consistent with long service life and easy reusability.
These issues are not very easily crammed into a single formula or two, but they are of crucial importance if one is trying to design for LEO access at lower cost per payload pound.
The other big issue is what are the true cost drivers. One-shot hardware is expensive, yes, but one of the real cost increasers is a very labor-intensive vehicle checkout and launch crew approach. The battlefield guys "solved" this with their missiles, which are systems a relatively small crew of not-intensively-trained soldiers can launch. They simplified it. A lot.
Another giant gorilla in the tent is a huge logistical "tail" to produce complicated articles, the kind of things needed to push a design "to the edge". You solve that one by backing off a tad on performance demands. That allows the simplification needed to minimize the manufacturing logistical "tail". It is folly to think a launcher will be low cost, if it does not have operational characteristics that, at least sort-of, resemble those of the launch and recovery and re-launch of a Piper Cub.
Compared to these gorillas, propellant costs are almost trivial. Kerosene is cheap, so is LOX. Even the hydrazines are not very expensive. Hydrogen itself is not that bad. And don't forget about ammonia: the X-15's "big engine" used that with LOX and did very well. One of the new rising stars is liquid methane.
Myself, I suspect the only things that might get added to this mix are some turbine or ramjet assist in the lower speed and altitude ranges on steep ascent trajectories (M0-6-ish, and SL-60kft-ish). Stages done as clusters of smaller modules allow far easier recovery of units for reuse. Here is where stowed wings and some sort of landing gear help on 1st stage items. They come back close to launch site anyway: might as well fly the "model airplanes" home and just land them on a runway.
I'm a little skeptical about "spaceplanes" ever carrying large payloads without some sort of nuclear engines. It's the "big airplane" structural problems that limit this approach. Smaller payloads: fine, it'll work. Think low ballistic coefficients at very shallow entry angles, and you can ease the heat shield problem some. A Piper Cub-style tubular frame covered with fire curtain cloth might just possibly be a viable outer skin for your airframe. No one yet knows for sure.
If you build a two stage spaceplane system (like the original shuttle proposals), then understand that at staging, it is speed, then path angle upward, then altitude, in that order, that you try to squeeze out of your design. With turbine as the (or one of the) powerplants in the first stage, you are limited to about 3.4 Mach for staging, and perhaps 70-100 kft. Add liquid injection cooling for the blading, and you might get Mach 3.8-ish out of it.
Plain subsonic combustion ramjet is good to right at Mach 6, but needs a booster between M0 and about M1.5, or it's just more dead weight at launch. Integral booster technologies for ramjet have existed since about 1970. Everything else it needs dates back from there to WW2. (Turbine has also been ready for this job since the 60's.)
Steep trajectories: you will be burning a blend of rocket and ramjet thrust to get vertical acceleration. And I don't mean combined-cycle exotic stuff. Parallel-burn is ready now, and has been for decades. I'd do it as strap-on pods, and stage-off the airbreathers as they run out of air 60-100 kft, then stage-off the first stage rocket core just about where we do now: near 10,000 fps, outside the sensible air.
The second stage is then just the same rocket stuff we already do, just the long-skirt vacuum nozzles, or a long aerospike.
Spaceplanes: thinking HTO/HL here. First stage is a hypersonic airbreather, maybe assisted by rockets. Second stage is a simple rocket plane. Gotta be clever, but my figures are showing that it will work at inert weights consistent with aircraft-like operational characteristics. Payload fraction to launch weight is always very low: well under 1%.
Big-airplane structural problem: part strengths scale as area (dimension squared, all else equal). Loads on parts scale as volume (due to weights), which is dimension cubed, all else being equal. That says part strength/weight ratios scale inversely with dimension, all else being equal. Twice as big is half as strong. relative to weight. That's why B-17 crews often walked away from belly landings while B-29 crews most often did not. Same inert weight fractions, B-29 1.4 times as large. Same basic aluminum structures. 70% as strong for the weight, which is vulnerable.
Just stuff to think about.
Pumps for liquid propellants: link didn't work. Turbopumps are a pretty mature technology. Xcor Aerospace has a positive displacement pump driven by a waste heat engine for their still-small engines. New rearrangement of some very old technologies, but it seems to work fine for them. I've seen it. Very simple, very robust.
Other types of rockets: High pressure tankage that also serves as primary airframe structure is a very good fit with either solid rockets or hybrid rockets, or even simple pressure-fed liquids. Not as structurally efficient, to be sure, but a very tough design approach that is very consistent with long service life and easy reusability.
These issues are not very easily crammed into a single formula or two, but they are of crucial importance if one is trying to design for LEO access at lower cost per payload pound.
The other big issue is what are the true cost drivers. One-shot hardware is expensive, yes, but one of the real cost increasers is a very labor-intensive vehicle checkout and launch crew approach. The battlefield guys "solved" this with their missiles, which are systems a relatively small crew of not-intensively-trained soldiers can launch. They simplified it. A lot.
Another giant gorilla in the tent is a huge logistical "tail" to produce complicated articles, the kind of things needed to push a design "to the edge". You solve that one by backing off a tad on performance demands. That allows the simplification needed to minimize the manufacturing logistical "tail". It is folly to think a launcher will be low cost, if it does not have operational characteristics that, at least sort-of, resemble those of the launch and recovery and re-launch of a Piper Cub.
Compared to these gorillas, propellant costs are almost trivial. Kerosene is cheap, so is LOX. Even the hydrazines are not very expensive. Hydrogen itself is not that bad. And don't forget about ammonia: the X-15's "big engine" used that with LOX and did very well. One of the new rising stars is liquid methane.
Myself, I suspect the only things that might get added to this mix are some turbine or ramjet assist in the lower speed and altitude ranges on steep ascent trajectories (M0-6-ish, and SL-60kft-ish). Stages done as clusters of smaller modules allow far easier recovery of units for reuse. Here is where stowed wings and some sort of landing gear help on 1st stage items. They come back close to launch site anyway: might as well fly the "model airplanes" home and just land them on a runway.
I'm a little skeptical about "spaceplanes" ever carrying large payloads without some sort of nuclear engines. It's the "big airplane" structural problems that limit this approach. Smaller payloads: fine, it'll work. Think low ballistic coefficients at very shallow entry angles, and you can ease the heat shield problem some. A Piper Cub-style tubular frame covered with fire curtain cloth might just possibly be a viable outer skin for your airframe. No one yet knows for sure.
If you build a two stage spaceplane system (like the original shuttle proposals), then understand that at staging, it is speed, then path angle upward, then altitude, in that order, that you try to squeeze out of your design. With turbine as the (or one of the) powerplants in the first stage, you are limited to about 3.4 Mach for staging, and perhaps 70-100 kft. Add liquid injection cooling for the blading, and you might get Mach 3.8-ish out of it.
Plain subsonic combustion ramjet is good to right at Mach 6, but needs a booster between M0 and about M1.5, or it's just more dead weight at launch. Integral booster technologies for ramjet have existed since about 1970. Everything else it needs dates back from there to WW2. (Turbine has also been ready for this job since the 60's.)
Steep trajectories: you will be burning a blend of rocket and ramjet thrust to get vertical acceleration. And I don't mean combined-cycle exotic stuff. Parallel-burn is ready now, and has been for decades. I'd do it as strap-on pods, and stage-off the airbreathers as they run out of air 60-100 kft, then stage-off the first stage rocket core just about where we do now: near 10,000 fps, outside the sensible air.
The second stage is then just the same rocket stuff we already do, just the long-skirt vacuum nozzles, or a long aerospike.
Spaceplanes: thinking HTO/HL here. First stage is a hypersonic airbreather, maybe assisted by rockets. Second stage is a simple rocket plane. Gotta be clever, but my figures are showing that it will work at inert weights consistent with aircraft-like operational characteristics. Payload fraction to launch weight is always very low: well under 1%.
Big-airplane structural problem: part strengths scale as area (dimension squared, all else equal). Loads on parts scale as volume (due to weights), which is dimension cubed, all else being equal. That says part strength/weight ratios scale inversely with dimension, all else being equal. Twice as big is half as strong. relative to weight. That's why B-17 crews often walked away from belly landings while B-29 crews most often did not. Same inert weight fractions, B-29 1.4 times as large. Same basic aluminum structures. 70% as strong for the weight, which is vulnerable.
Just stuff to think about.
GW Johnson
McGregor, Texas
McGregor, Texas
-
GIThruster
- Posts: 4686
- Joined: Tue May 25, 2010 8:17 pm
Sorry, I'm not familiar with the pump.
As to my manner of quickly attacking, I can only explain that I've seen this idea dozens of times over the last half decade and posted on it here several times. I'm not a supporter for the reasons stated.
No one likes to repeat themselves and I admit to some self-interest--that it irks me things like this that make no economic sense, get the grant funds and M-E research has not for 5 years now.
Just irks. . .
Now if NASA would revive their M-E research program at Marshall, I'd be happier (though still a little intolerant for economically senseless approaches to spaceflight..
As to my manner of quickly attacking, I can only explain that I've seen this idea dozens of times over the last half decade and posted on it here several times. I'm not a supporter for the reasons stated.
No one likes to repeat themselves and I admit to some self-interest--that it irks me things like this that make no economic sense, get the grant funds and M-E research has not for 5 years now.
Just irks. . .
Now if NASA would revive their M-E research program at Marshall, I'd be happier (though still a little intolerant for economically senseless approaches to spaceflight..
"Courage is not just a virtue, but the form of every virtue at the testing point." C. S. Lewis
"I was going to ask your opinion of the Flowmetrics pistonless Turbo Pump replacement, but Flowmetrics appears to have killed all references to it. I suppose that means they discovered why it wasn't practical."
No it works fine. They just discovered they can't enforce their patent--it's been done before. Turbo pump ISPs at turbo pump dry weights, but dirt simple and you gas and go.
But they can't get a royalty.
No it works fine. They just discovered they can't enforce their patent--it's been done before. Turbo pump ISPs at turbo pump dry weights, but dirt simple and you gas and go.
But they can't get a royalty.
molon labe
montani semper liberi
para fides paternae patria
montani semper liberi
para fides paternae patria
-
CaptainBeowulf
- Posts: 498
- Joined: Sat Nov 07, 2009 12:35 am
Rockets seem best for the indefinite future.
Improvements can be found in lighter weight tankage. Carbon fiber, maybe, that would give you an extra 10 to 20% payload fraction. If a fusion system like polywell can be adapted to work similarly to a nerva type rocket, maybe a big improvement in ISP and thrust is also available... but has to be balanced against the increased weight of the reactor.
I'm holding out for some sort of field propulsion breakthrough. Many people have tried - Heim, Podkletnov, Ning Li... Tajmar seems the most credible, but even there the results are inconclusive. However, there seems to be enough work that is suggestive of something in terms of gravitomagnetic fields that it may pan out in the next few decades.
Improvements can be found in lighter weight tankage. Carbon fiber, maybe, that would give you an extra 10 to 20% payload fraction. If a fusion system like polywell can be adapted to work similarly to a nerva type rocket, maybe a big improvement in ISP and thrust is also available... but has to be balanced against the increased weight of the reactor.
I'm holding out for some sort of field propulsion breakthrough. Many people have tried - Heim, Podkletnov, Ning Li... Tajmar seems the most credible, but even there the results are inconclusive. However, there seems to be enough work that is suggestive of something in terms of gravitomagnetic fields that it may pan out in the next few decades.
-
rjaypeters
- Posts: 869
- Joined: Fri Aug 20, 2010 2:04 pm
- Location: Summerville SC, USA
Could it be?
While SpaceShipTwo is designed to make short joyrides to suborbital space, Virgin Galactic has set its sights on orbital travel, too.
"Obviously, we want to move on to orbital after we've got suborbital under our belts, and maybe even before that," Branson said.
The company will aim to win a NASA contract to transport astronauts to the International Space Station, he said. The space agency plans to look to private space companies to take over this task once the space shuttle fleet retires next year.
"We plan to start work on an orbital program quite quickly," Branson said.
End quote.
Read the Spaceport runway christening report:
http://www.space.com/news/spaceport-ame ... 01022.html
Quote:rjaypeters wrote:... FWIW, I'm suspecting Burt Rutan will develop Spaceship Three as a Black Horse variant for TSTO and who knows what after?
While SpaceShipTwo is designed to make short joyrides to suborbital space, Virgin Galactic has set its sights on orbital travel, too.
"Obviously, we want to move on to orbital after we've got suborbital under our belts, and maybe even before that," Branson said.
The company will aim to win a NASA contract to transport astronauts to the International Space Station, he said. The space agency plans to look to private space companies to take over this task once the space shuttle fleet retires next year.
"We plan to start work on an orbital program quite quickly," Branson said.
End quote.
Read the Spaceport runway christening report:
http://www.space.com/news/spaceport-ame ... 01022.html
"Aqaba! By Land!" T. E. Lawrence
R. Peters
R. Peters
-
GW Johnson
- Posts: 85
- Joined: Sat Sep 11, 2010 9:14 pm
- Location: McGregor, TX USA
- Contact:
Going to be interesting to see how Branson or any of the rest address orbital spaceflight. Compared to suborbital, quite the different problem. Mass ratio - Isp is far more demanding. Heating (both ascent and most especially reentry) is way to hell and gone far more demanding.
The old guys who did this before are dying off. Soon. I was an old solid rocket and ramjet missile guy. Found out this last summer that I am one of America's last surviving full-capability ramjet engineers. This is not good.
The old guys who did this before are dying off. Soon. I was an old solid rocket and ramjet missile guy. Found out this last summer that I am one of America's last surviving full-capability ramjet engineers. This is not good.
GW Johnson
McGregor, Texas
McGregor, Texas