What changes has Obama made to NASA?

[Shackleford]

Both the Air Force and NASA spend some R&D money on truly nutty ideas, some of which even violate the laws of physics. The rationale behind investing R&D money in nutty ideas is that even though the odds of success are extremely small, the payback will be truly immense if the ideas do somehow pan out.

NASA and the Air Force have been putting sometimes small, sometimes large amounts of money into an SSTO vehicle for a long, long, long time, at least since the 1960s. The concept of an SSTO vehicle has long had a small coterie of aficionados. They even managed to convince Ronald Reagan to announce in his 1986 State of the Union address a desire to create "a new Orient Express that could, by the end of the next decade, take off from Dulles Airport, accelerate up to 25 times the speed of sound, attaining low Earth orbit or flying to Tokyo within two hours." This led to an eight year boondoggle, the National Aero-Space Plane. The idea keeps coming back because even though the odds of success are extremely small the potential for payback is immense.

Do note the similarity in phrasing between the last sentences of the first and second paragraphs.
Tiny steps? Yes. Meaningful steps? No. An SSTO vehicle is still a pipe dream. While investing small amounts of R&D money in a pipe dream is not necessarily a stupid idea, pinning ones hopes on a pipe dream is a very stupid idea.

Hm. What makes the technology a pipe dream? What do you think is the next revolutionary propulsion technology? Is there even one on the horizon?

 

[Shackleford]

EditI see that you have not yet answered any of the questions I raised in post #67.

That document is from 1995. Some questions:

1. What makes you think that NASA was not a part of those efforts?

I don't. I'm sure NASA was involved.

2. Has a viable trans-atmospheric vehicle been developed in the 15 years that have passed since the publication of that document?

Isn't there currently an Air Force or DARPA test vehicle out there?

3. What makes you think that trans-atmospheric vehicles are the one and only answer to the problem of access to space?

I don't. I don't know of anything else, other than the ion-propulsion technology.

4. What if the apparently insurmountable problems that make the answer to question #2 "no" are just that, insurmountable problems?

Well, if I knew what they were, I'm sure I'd agree with you. Clearly, I'm not all that informed in this area. I've heard a few things here and there from someone who was in the military and is currently at NASA.

...

 

[D H]

Hm. What makes the technology a pipe dream? What do you think is the next revolutionary propulsion technology? Is there even one on the horizon?

Just as a starter,

1. Shock layer heating. One of the unfortunate side effects of traveling at Mach 5 is that the vehicle has a tendency to melt. Orbital speed is Mach 25.
2. The rocket equation. A chemical SSTO rocket that goes into orbit and that carries its own fuel and oxidizer has to be 96% or more fuel and oxidizer. That 4% that is not fuel includes fuel tanks and rockets.
3. There is one way out of this morass: Get the oxidizer from the atmosphere, the way a normal jet aircraft does. There is a problem with this concept. Blow on a candle and it goes out. A scramjet engine is a candle being blown on by a wind in excess of Mach 5. Orbital speed is Mach 25.
4. The highest speed that has been attained is Mach 5 by the X-51 for a total of 200 seconds by a tiny little vehicle. X-51 is intended to get to Mach 6. Orbital speed is Mach 25.
5. Getting past Mach 17 is not even in the realm of sci-fi. It is in the realm of fantasy.
6. Just in case you didn't notice it before, orbital speed is Mach 25.

 

[Shackleford]

Just as a starter,

1. Shock layer heating. One of the unfortunate side effects of traveling at Mach 5 is that the vehicle has a tendency to melt. Orbital speed is Mach 25.
2. The rocket equation. A chemical SSTO rocket that goes into orbit and that carries its own fuel and oxidizer has to be 96% or more fuel and oxidizer. That 4% that is not fuel includes fuel tanks and rockets.
3. There is one way out of this morass: Get the oxidizer from the atmosphere, the way a normal jet aircraft does. There is a problem with this concept. Blow on a candle and it goes out. A scramjet engine is a candle being blown on by a wind in excess of Mach 5. Orbital speed is Mach 25.
4. The highest speed that has been attained is Mach 5 by the X-51 for a total of 200 seconds by a tiny little vehicle. X-51 is intended to get to Mach 6. Orbital speed is Mach 25.
5. Getting past Mach 17 is not even in the realm of sci-fi. It is in the realm of fantasy.
6. Just in case you didn't notice it before, orbital speed is Mach 25.

Okay. I didn't know its performance was that far short.

What do you think is the next revolutionary propulsion technology? Is there even one on the horizon?

 

[D H]

What do you think is the next revolutionary propulsion technology?

There are lots of things in the pipeline. Scramjets are one. VASIMR, solar sails, rail launchers: All are being researched. Which one will come out the winner, no telling. Picking a winner from the slew of technologies being researched by the Air Force, DARPA, and NASA before it is ready is a dumb idea.

Is there even one on the horizon?

VASIMR looks very promising as a technique for keeping the ISS in orbit. However, VASIMR is useless as a launch technology and is of limited use as a means of getting people beyond low Earth orbit. Beyond that, it depends on what you mean by horizon. If you mean something that could be put into use now to get people into space or beyond low Earth orbit, absolutely not.

 

[Shackleford]

There are lots of things in the pipeline. Scramjets are one. VASIMR, solar sails, rail launchers: All are being researched. Which one will come out the winner, no telling. Picking a winner from the slew of technologies being researched by the Air Force, DARPA, and NASA before it is ready is a dumb idea.


VASIMR looks very promising as a technique for keeping the ISS in orbit. However, VASIMR is useless as a launch technology and is of limited use as a means of getting people beyond low Earth orbit. Beyond that, it depends on what you mean by horizon. If you mean something that could be put into use now to get people into space or beyond low Earth orbit, absolutely not.

So, then it's still sci-fi at this point.

 

[D H]

All of those perpetually low TRL technologies are sci-fi at this point. Something will pop up, but what that something is, nobody knows. Picking a winner prematurely is not the answer because the odds are that in reality that winner is a loser. A lot (and I mean a lot; tens of billions) has been spent on trans-atmospheric flight with nothing to show. The same goes for fusion rockets and, to a lesser extent, laser-powered propulsion. Each of those represents a technology chosen prematurely because they have powerful constituencies behind them.

 

[Shackleford]

All of those perpetually low TRL technologies are sci-fi at this point. Something will pop up, but what that something is, nobody knows. Picking a winner prematurely is not the answer because the odds are that in reality that winner is a loser. A lot (and I mean a lot; tens of billions) has been spent on trans-atmospheric flight with nothing to show. The same goes for fusion rockets and, to a lesser extent, laser-powered propulsion. Each of those represents a technology chosen prematurely because they have powerful constituencies behind them.

Because of this thread, an article on this caught my attention. Of course, now, I'm skeptical.

http://www.spacedev.com/spacedev_advanced_systems.php

 

[D H]

Because of this thread, an article on this caught my attention. Of course, now, I'm skeptical.

http://www.spacedev.com/spacedev_advanced_systems.php

That is nothing like the trans-atmospheric vehicles you wrote about earlier. This is old-style stuff. It uses a commercial rocket for launch, a heat shield for reentry, and a lifting body for descent and landing. No scramjets, no SSTO. This is similar to the Shuttle system, which also uses disposable rockets for launch, a heat shield for reentry, and a lifting body for descent and landing.

Unlike the side-mounted Shuttle, this vehicle is perched atop the launch vehicle. The Columbia disaster was a consequence of the Shuttle's side-mount configuration. Unlike the Shuttle, this vehicle does not have a 1000 km cross-range capability. In other words, the Dream Chaser will not be able to launch from Vandenburg, snatch a Russian spy satellite out of its orbit, and return to Vandenburg one rev later with no one the wiser as to what happened. That is not a big loss.

 

[MattRob]

I think if NASA was a little larger than we'd be doing a lot more in space. In TEN YEARS, we went from no human having ever gone into space, to landing on the moon. Just two years before that decade, 1957, the first satellite went in orbit. Twelve years before then, the first intercontinental missiles were launched from Peenemünde, the V-2's at Great Britain. We went from liquid-fueled rockets being a fancy but useless system, a "pipe dream", in 1930, to the first practical guided, space-fairing rockets in 1942, to the first "pipe dream" satellite in orbit in 1957, to the "pipe dream" of meeting another vehicle IN ORBIT in 1965 with Gemini, to perhaps the most ludicrous, monstrous "dumb, pipe dream" of sending a 33-story, multi-million pound, 3-staged rocket, (5 stages if you count the vehicles as stages), take three men into space in two separate vehicles, which re-oriented and docked en route, entered orbit, landed on the moon, lifted off, and docked in Lunar orbit, and returned to Earth. And then we did it SIX more times. I never want to hear "pipe dream" again. All it takes is willpower. If we had this kind of willpower to get an Orbital Elevator working, it would be working. If the nation were this united to make an SSTO, we would have an SSTO. It seems all imagination (which now carries a negative connotation) and vision have been completely stripped from American society, perhaps because we don't have something like Apollo anymore to prove what's possible. Because Congressmen have decided that making some vision and real hope for Americans isn't even worth HALF OF ONE PERCENT of their budget.
</rant>

Just as a starter,

1. Shock layer heating. One of the unfortunate side effects of traveling at Mach 5 is that the vehicle has a tendency to melt. Orbital speed is Mach 25.
2. The rocket equation. A chemical SSTO rocket that goes into orbit and that carries its own fuel and oxidizer has to be 96% or more fuel and oxidizer. That 4% that is not fuel includes fuel tanks and rockets.
3. There is one way out of this morass: Get the oxidizer from the atmosphere, the way a normal jet aircraft does. There is a problem with this concept. Blow on a candle and it goes out. A scramjet engine is a candle being blown on by a wind in excess of Mach 5. Orbital speed is Mach 25.
4. The highest speed that has been attained is Mach 5 by the X-51 for a total of 200 seconds by a tiny little vehicle. X-51 is intended to get to Mach 6. Orbital speed is Mach 25.
5. Getting past Mach 17 is not even in the realm of sci-fi. It is in the realm of fantasy.
6. Just in case you didn't notice it before, orbital speed is Mach 25.

Personally, I don't see why there's so much fuss against scramjets. From what I understand, they can produce more thrust than drag from mach 4 up, and involve no moving parts aside from fuel injectors. (No fans, etc.). From what I understand of the Scramjet, the issue it faces is that shock layer heating. It requires too much speed for a given dynamic pressure, and current heat shielding technology can't handle it. But this is what gets me. Ablative heat shields have survived re-entry on JUPITER at 230 G's, I hardly see how we can't handle mach 4 even at sea level. Maybe ablative heat shields aren't reusable but surely they can be made for more than one use, and a 2-3 use scramjet sled with a Specific Impulse of 20,000-40,000 all the way to whatever speed you want with hardly any moving parts is bound to be far cheaper than a 750-ton LH2/LOX External Tank and 3 SSME's.
(Sled? I meant booster.)

And I've never heard of the "blowing out the candle". I always thought the heat for ignition came from the mach 4 shockwaves in the engine, so the fuel was constantly lit.

My main concern is a lot of the arguments seem to be applicable to ALL space vehicles (1,4,5,6). And space vehicles CERTAINLY are NOT impossible. It's interesting that no matter how many times people think something is ridiculous, mock it, and are proven wrong by time, people keep doing it. Sure some things really are crazy, but I think mockeries are thrown around a bit too lightly. After all, we did land on the moon...

So what about now? The thread topic is NASA's current future, I highly doubt my obscure post on Physics Forums will drive NASA to investigate ideas seriously and develop a cheap system, last I heard it's going to be 5 years for Dragon 9 to be man-rated.

My rant for manned spaceflight will come tomorrow when I'm not so tired and my thoughts are better organized...

 

[twofish-quant]

What do you think is the next revolutionary propulsion technology? Is there even one on the horizon?

Going low tech.

The US has this fascination with gee-whiz, revolutionary technology. Sometimes you are lucky and those technologies allow for basic breakthroughs in some areas. The trouble is that it appears that getting stuff into LEO cheaply isn't one of those areas, which is why the Russians and Chinese seem to be better at this.

There's nothing fundamentally revolutionary about what the Russians and Chinese are doing, they are just taking technology that has been around for the last fifty years and making it work. Same with the commercial space ventures. SpaceX is out to make a profit, and in some areas, you make profits by using boring technology that has been around for the last fifty years.

 

[twofish-quant]

All it takes is willpower. If we had this kind of willpower to get an Orbital Elevator working, it would be working.

You can't get around basic laws of physics through willpower. You can sometimes get around a basic law of physics through clever engineering, but that's something different.

Because Congressmen have decided that making some vision and real hope for Americans isn't even worth HALF OF ONE PERCENT of their budget.

Hardly. The problem isn't lack of vision. The problem is that different people have different visions. If you ask most astrophysicists, they'd prefer if the US gets totally out of the manned space flight business, because robots are *MUCH* more effective at doing science.

Personally, I don't see why there's so much fuss against scramjets.

Laws of physics and that sort of thing.

Maybe ablative heat shields aren't reusable but surely they can be made for more than one use, and a 2-3 use scramjet sled with a Specific Impulse of 20,000-40,000 all the way to whatever speed you want with hardly any moving parts is bound to be far cheaper than a 750-ton LH2/LOX External Tank and 3 SSME's.

It turns out that most of the expense of space flight is in fixed costs, particularly labor. You can dramatically reduce costs by setting up an assembly line with cheap labor and then cracking out rockets by the truckload (i.e. stuff that China and Russia are good at). That works in favor of throwaway boosters and against anything reusable. If you go high tech, then the skill level of the people that are working on the rockets go up, and you can't get a community college level educated person to put wire A into part B.

It's interesting that no matter how many times people think something is ridiculous, mock it, and are proven wrong by time, people keep doing it.

Sometimes the naysayers are right.

 

[D H]

If you ask most astrophysicists, they'd prefer if the US gets totally out of the manned space flight business, because robots are *MUCH* more effective at doing science.

Read post #64, please.

 

[Shackleford]

Going low tech.

The US has this fascination with gee-whiz, revolutionary technology. Sometimes you are lucky and those technologies allow for basic breakthroughs in some areas. The trouble is that it appears that getting stuff into LEO cheaply isn't one of those areas, which is why the Russians and Chinese seem to be better at this.

There's nothing fundamentally revolutionary about what the Russians and Chinese are doing, they are just taking technology that has been around for the last fifty years and making it work. Same with the commercial space ventures. SpaceX is out to make a profit, and in some areas, you make profits by using boring technology that has been around for the last fifty years.

Then the most efficient way to get someone into orbit is also the most inefficient way, by just blasting through the atmosphere.

I'm curious if it's any more efficient to go up through a low-pressure system in the atmosphere?

 

[twofish-quant]

Read post #64, please.

I tend to agree with you, but in the interests of giving astrophysicists who hate manned space program a far hearing then...

1) A lot of the animus is not directed at manned space flight in general, but specifically project Constellation. The problem is that Constellation is a budgetary train wreck. If NASA funding is constant and if Constellation goes through according to 2008 plans, then by 2020, Constellation will eat up all of NASA's budget, and at that point the belief is that Constellation will try to kick unmanned space programs and science out of the boat. A healthy manned space program may increase funding for science, but no one thinks Constellation with current funding is viable. If you look ahead at the most likely outcome, you'll have a budgetary train wreck in 2020 and the only two politically viable options would be to squeeze out unmanned space flight or stop Constellation, and astrophysicists would rather have that conversation now.

Conversely, I don't know of any astrophysicist that is against the SpaceX program. The reason being is that if that program falls apart it's not going to have any impact on unmanned spacecraft .

2) Astrophysicists aren't experts at politics. Lobbyists, marketers, and politicians are. There may be (and I think there are) great political reasons for manned space flight. However, those political reasons have to take into account that if the question is how much astronomy can be done for how much money, then the answer is "don't use people." That might not be the right question, but it's the question that astrophysicists have the most expertise in.

3) A great manned space program may help astronomy, but we don't have a great manned space program, and astronomers are still smarting over the Hubble fiasco. The problem with Hubble was that it was designed with the assumption that routine manned space flights were possible, and when that turned out not to be true, it put to whole program in danger. It's not so much jealousy that motivates astrophysicists, but rather fear and anger.

Personally, I don't think that you can come up with an argument that makes astrophysicists strong supporters of manned space flight. What I think is possible is to turn them from being highly negative to somewhat negative or neutral. If you set up the budgets so that manned space flight cannot have negative impacts on unmanned space flight (perhaps by moving the costs into a separate line item) then you've changed the situation.

 

[twofish-quant]

Then the most efficient way to get someone into orbit is also the most inefficient way, by just blasting through the atmosphere.

Define efficient. If you define it in $$$$ terms, then you'll find that in 2011, trying to build a air-breathing spacecraft is an extremely bad idea.

Ironically, this is the sort of thing that killed the central planned economies of Russia and China. Without market prices, you have no way of even measuring economic efficiency, and so you end up with projects that just eat up huge amounts of resources that could have been used for other things.

If you are talking physics, then it turns out that rockets are more "efficient" than air-breathers since you go straight up out the atmosphere, whereas if you have an air-breather, you have to take a trajectory that keeps you in the atmosphere for much longer. Then there is gravity. While you are in a suborbital trajectory, you have to expend energy to keep from falling down. You minimize those losses by going straight up as quickly as you can.

 

[MattRob]

You can't get around basic laws of physics through willpower. You can sometimes get around a basic law of physics through clever engineering, but that's something different.

True, but there's nothing fundamentally impossible with some of these concepts. We're not trying to rewrite physics, we're building an orbital elevator. I don't think there're any equations which clearly state that that's impossible. Sure it takes some really advanced materials and a LOT of them (skyrocketing the costs through the thermosphere, literally), but fundamentally possible. But "willpower" on part of the population, means much more funding, which means many more resources, engineers, and possibly even better engineers.

Laws of physics and that sort of thing.

Okay, what laws of physics? Heat + Oxygen + Fuel = Combustion. Heat is shockwaves in the engine, fuel is injected, oxygen is in the atmosphere. The air heats up and expands in the engine, causing it to leave faster than it entered, causing a net gain in velocity as it travels outwards, and law of conservation of momentum accelerates vehicle forward. How is this impossible?

It turns out that most of the expense of space flight is in fixed costs, particularly labor. You can dramatically reduce costs by setting up an assembly line with cheap labor and then cracking out rockets by the truckload (i.e. stuff that China and Russia are good at). That works in favor of throwaway boosters and against anything reusable. If you go high tech, then the skill level of the people that are working on the rockets go up, and you can't get a community college level educated person to put wire A into part B.

Can't argue with that. But you can only cheap down space launch so much. And, like I said, if a fully reusable system with a short turnaround time can be developed, then because the supply of lifting ability is going to go so far up, it's going to get a lot cheaper. There's a gruesome limit on turnaround time when you have to re-build the entire, or even just part of, the rocket every time. I'm no expert, but I think I can say just from basics that if a system has a turnaround time of less than a week, it would lower prices drastically, if it has any meaningful lift capacity at all. This is why I like the idea of scramjets so much. With that you simply don't need staging or a huge mass ratio. And the simplicity of the engine means not a lot of maintenance, though the cooling system is a whole different story.

What about something like the White Knight/Spaceship One - type "mothership" configuration? Make a "carrier" aircraft with LOX-RP1 rockets, after MECO it detaches, "orbiter" ascends to orbit, mothership switches to turbofan engines to allow it to fly back to the launch site.
Two stages, though both aren't just reusable, but airplane-like. Perhaps even a practical turnaround time less than three weeks if engineered correctly? Have the orbiter attach to the bottom. No cranes, no V.A.B. assembly, no launchpad, even. Just some maintenance, fill the tanks, line up on a runway and it's ready to fly again, just like that. Forget the idea of big, cylindrical, take-it-around-on-a-crawler rocket that needs a launch tower and launchpad. All that only increases turnaround time and maintenance. What's wrong with making the first stage really airplane-like? A Me-163 with modern fuels and a juiced-up mass ratio? With the orbiter simply having to attach to the underside like an MXY-7, drastically reducing time and complexity of assembly. Except, as opposed to the early rocket-planes, use modern fuels such as LOX-LH2 and/or LOX-RP1. Heck, I just worked out the math and the mass ratios wouldn't have to be far above 3 if it DID use LH2/LOX. About half of the Space Shuttle+ET assembly! With RP-1/LOX it would have to be a little above 7.

- Not a big fan of LH-2. I think it's just crazy to use something that cold. Isn't that a source of a lot of the maintenance needed for the Shuttle, because it has to work with something that incredibly cold? And the Columbia incident was because of the insane insulation needed to keep it at -424 *F!
(meanwhile LOX at -298 *F and RP1 at room temperature.)

 

[chiro]

two-fish I'd like to ask you a question.

Space-ships rely on the simple principle of having a net directed force that is in the direction of space. Its simple physics 101. You exert a net-force on an object that is greater than the natural forces holding that something in place (ie gravity) and your vehicle then heads in the direction of the net-force. (I know its simplified but I just wanted to get the main idea across).

Now with the definition of energy and work we need a mechanism to provide that force. Without getting into the details of energy conversion and associated mechanisms (like thermodynamics), we know that if we can get some device to take some energy source and convert it into force, then we have liftoff.

Now currently we are stuck in an energy stoneage with oil based energy. But why does that have to be a restriction of "the laws of physics"? Do you believe that we won't discover other forms of energy generation in the future that can give us our "net-force" in ways that are better than the standard "oil" route?

If a new energy source and utilization process is found it won't break "the laws of physics". The laws of physics don't say that we have to use "oil" as our energy reservoir.

Now to get to my question. Do you really think the laws of physics forbid us to discover a better energy source that is cheaper, abundant, more efficient, and portable to allow mankind to overcome the current barriers in space-travel?

 

[MattRob]

I'm not Two-Fish but I'll reply, or at least comment, anyways. We're not entirely dependent on oil for all our power. There's Nuclear energy, hydroelectric energy, coal power, natural gas, and of course the less mainstream but ever present solar and wind power. Just to name a few. I highly disagree with saying we're in an "energy stoneage", nuclear power is quiet an accomplishment, and we're on the brink of harnessing FUSION power, that can power a city with the hydrogen in a bucket of water. Cars run on "Oil", a highly processed hydrocarbon solution known as Gasoline, by chemically reacting with oxygen to produce heat and drive an amazingly intricate piston engine, an invention I believe was many, many decades ahead of it's time. In principle, a car engine is far more complicated than a rocket engine. (Though that's hardly true in practice, but it is true for certain rockets.) And, interestingly enough, a piston engine relies on a combustible fuel, so it doesn't have to be a hydrocarbon, it's just those are the most cheap and easily available. Cars (Piston engines) could, theoretically, run on any combustible fluid. Alcohol could be an option. And I'm sure there're more non-oil based combustibles than that, that's just off the top of my head.

A Rocket engine does not use "oil", or any form of hydrocarbon, for it's energy reservoir, unless it's a LOX-RP1 engine (Liquid Oxygen, Rocket Propellant One, a type of Kerosene made specifically for rockets), which is used in cheaper, less complicated launch systems. The Space Shuttle, for instance, uses Liquid Hydrogen and Liquid Oxygen, so did the upper stages of the Saturn-V. The engines in-orbit use a hydrazine/nitrogen-oxide combination. (To be specific, Monomethylhydrazine/Dinitrogen-Tetroxide, used on Space Shuttle Orbital Menuvering engines and the Apollo's Command Module SPS orbital menuvering engine.) The Earliest liquid-fuelled rockets ran on Alcohol or Hydrogen peroxide. Solid Rockets run on ammonium perchlorate, though that's certainly not the only option. By far, in terms of performance, LOX/LH2 is the best oxidizer/fuel combination. In terms of price efficiency... Maybe, maybe not. I don't know and I don't know if anyone knows. If someone knew then I assume every engine would use one or the other, but some engines use one and some engines use the other. LOX/RP-1 has lower performance but is much easier to handle and work with, hence, cheaper. Though because it has lower performance it requires a bigger rocket with more fuel.

I'm sorry, but buzzwords annoy me, and with the whole "green" movement going on, "Oil-based society" and "energy stoneage" really seem more political than scientific.

Now, to reply, we don't use "oil" as our energy reservoir in rockets. Only a very specific fuel out of many different options available use oil, and there's no reason to think of hydrocarbons as low-tech. They're a readily available, cheap, abundant, efficient and portable source of power. Though you're right in that they don't provide as much power as we'd like, though we could always want more power, though spaceflight is very demanding.

Sorry, I'll let Two-Fish answer now...

 

[Shackleford]

Define efficient. If you define it in $$$$ terms, then you'll find that in 2011, trying to build a air-breathing spacecraft is an extremely bad idea.

Ironically, this is the sort of thing that killed the central planned economies of Russia and China. Without market prices, you have no way of even measuring economic efficiency, and so you end up with projects that just eat up huge amounts of resources that could have been used for other things.

If you are talking physics, then it turns out that rockets are more "efficient" than air-breathers since you go straight up out the atmosphere, whereas if you have an air-breather, you have to take a trajectory that keeps you in the atmosphere for much longer. Then there is gravity. While you are in a suborbital trajectory, you have to expend energy to keep from falling down. You minimize those losses by going straight up as quickly as you can.

I think it was the entire Communist-flavored iteration of Marxism that killed the economies of Russia and China, but I'm sure we're diametrically opposed on this point.

I was talking about physics. Is it actually more efficient in terms of energy? There's an incredible amount of friction from the atmosphere when you plow straight through it at those tremendous speeds. Still, you would have to do a lot of work against the gravitational force with the air-breathers.

 

[Ryker]

I think it was the entire Communist-flavored iteration of Marxism that killed the economies of Russia and China, but I'm sure we're diametrically opposed on this point.

So if you disagree with twofish, what feature of communism was it that killed the economies then? Because you do realize he did mention one such feature of the "communist-flavored iteration of Marxism", right? You seem to be just tossing the word around without any substance behind your "arguments", and I find it very odd that people in this day and age still see the world as "red" and the rest. I guess the conservative US propaganda really does still hold sway over the fears of Americans.

 

[twofish-quant]

True, but there's nothing fundamentally impossible with some of these concepts.

Fundamentally impossible no. Fundamentally extremely difficult requiring large amounts of expensive research to figure out ways around those issues, yes. For example SSTO is limited by the rocket equation which means that given a specific impulse, you need fraction X of weight in the rocket and fraction Y in fuel.

Sure it takes some really advanced materials and a LOT of them (skyrocketing the costs through the thermosphere, literally), but fundamentally possible.

Which requires $X billion in research with probability Y of success.

But "willpower" on part of the population, means much more funding, which means many more resources, engineers, and possibly even better engineers.

Which then requires an economic system to generate the wealth necessary to get things done.

Okay, what laws of physics? Heat + Oxygen + Fuel = Combustion. Heat is shockwaves in the engine, fuel is injected, oxygen is in the atmosphere. The air heats up and expands in the engine, causing it to leave faster than it entered, causing a net gain in velocity as it travels outwards, and law of conservation of momentum accelerates vehicle forward. How is this impossible?

It's not. Jet aircraft do it all the time. However if you want to go to Mach 25, then you run into the amount of energy that is in the fuels, and then you run into frictional heating. Also, to tell if something is impossible or not, you have to run numbers. In the case of SSTO spacecraft , you have to have materials with a certain level of energy content, a certain weight, and certain structural characteristics.







Can't argue with that. But you can only cheap down space launch so much. And, like I said, if a fully reusable system with a short turnaround time can be developed, then because the supply of lifting ability is going to go so far up, it's going to get a lot cheaper. There's a gruesome limit on turnaround time when you have to re-build the entire, or even just part of, the rocket every time. I'm no expert, but I think I can say just from basics that if a system has a turnaround time of less than a week, it would lower prices drastically, if it has any meaningful lift capacity at all. This is why I like the idea of scramjets so much. With that you simply don't need staging or a huge mass ratio. And the simplicity of the engine means not a lot of maintenance, though the cooling system is a whole different story.

What about something like the White Knight/Spaceship One - type "mothership" configuration? Make a "carrier" aircraft with LOX-RP1 rockets, after MECO it detaches, "orbiter" ascends to orbit, mothership switches to turbofan engines to allow it to fly back to the launch site.
Two stages, though both aren't just reusable, but airplane-like. Perhaps even a practical turnaround time less than three weeks if engineered correctly? Have the orbiter attach to the bottom. No cranes, no V.A.B. assembly, no launchpad, even. Just some maintenance, fill the tanks, line up on a runway and it's ready to fly again, just like that. Forget the idea of big, cylindrical, take-it-around-on-a-crawler rocket that needs a launch tower and launchpad. All that only increases turnaround time and maintenance. What's wrong with making the first stage really airplane-like? A Me-163 with modern fuels and a juiced-up mass ratio? With the orbiter simply having to attach to the underside like an MXY-7, drastically reducing time and complexity of assembly. Except, as opposed to the early rocket-planes, use modern fuels such as LOX-LH2 and/or LOX-RP1. Heck, I just worked out the math and the mass ratios wouldn't have to be far above 3 if it DID use LH2/LOX. About half of the Space Shuttle+ET assembly! With RP-1/LOX it would have to be a little above 7.

- Not a big fan of LH-2. I think it's just crazy to use something that cold. Isn't that a source of a lot of the maintenance needed for the Shuttle, because it has to work with something that incredibly cold? And the Columbia incident was because of the insane insulation needed to keep it at -424 *F!
(meanwhile LOX at -298 *F and RP1 at room temperature.)[/QUOTE]

 

[twofish-quant]

Now currently we are stuck in an energy stoneage with oil based energy. But why does that have to be a restriction of "the laws of physics"?

That's not the problem. If you restrict yourself to any sort of chemical rocket, then you can get a specific impulse of at most about 450 seconds. If you start working on solid nuclear rockets, then you can get Isp up to 1200. With air breathing spacecraft you can get Isp up to 2500 seconds.

Once you have the number of the specific impulse, then you plug those numbers into the rocket equation, and that gives you the limits for what your fuel fraction is, and at that point you start figuring out what you make the rocket out of.

Now you can get rid of the problem by putting the source of the power on the ground. The trouble with that is that we have done enough research in jets and rockets to know what the basic problems are. We haven't done that research in laser powered boosters.

If a new energy source and utilization process is found it won't break "the laws of physics".

The two sources right now are chemical and nuclear fission.

Do you really think the laws of physics forbid us to discover a better energy source that is cheaper, abundant, more efficient, and portable to allow mankind to overcome the current barriers in space-travel?

In the next two decades, yes. If there is some source of energy outside of chemical and nuclear that we don't know about, it's going to be really subtle, and if we haven't found it yet, we aren't going to find it anytime soon.

And if there are no sources of energy, then there are no sources of energy.

Now if you think that the laws of themodynamics don't hold them all bets are off.

 

[chiro]

I'm not Two-Fish but I'll reply, or at least comment, anyways. We're not entirely dependent on oil for all our power. There's Nuclear energy, hydroelectric energy, coal power, natural gas, and of course the less mainstream but ever present solar and wind power. Just to name a few. I highly disagree with saying we're in an "energy stoneage", nuclear power is quiet an accomplishment, and we're on the brink of harnessing FUSION power, that can power a city with the hydrogen in a bucket of water. Cars run on "Oil", a highly processed hydrocarbon solution known as Gasoline, by chemically reacting with oxygen to produce heat and drive an amazingly intricate piston engine, an invention I believe was many, many decades ahead of it's time. In principle, a car engine is far more complicated than a rocket engine. (Though that's hardly true in practice, but it is true for certain rockets.) And, interestingly enough, a piston engine relies on a combustible fuel, so it doesn't have to be a hydrocarbon, it's just those are the most cheap and easily available. Cars (Piston engines) could, theoretically, run on any combustible fluid. Alcohol could be an option. And I'm sure there're more non-oil based combustibles than that, that's just off the top of my head.

A Rocket engine does not use "oil", or any form of hydrocarbon, for it's energy reservoir, unless it's a LOX-RP1 engine (Liquid Oxygen, Rocket Propellant One, a type of Kerosene made specifically for rockets), which is used in cheaper, less complicated launch systems. The Space Shuttle, for instance, uses Liquid Hydrogen and Liquid Oxygen, so did the upper stages of the Saturn-V. The engines in-orbit use a hydrazine/nitrogen-oxide combination. (To be specific, Monomethylhydrazine/Dinitrogen-Tetroxide, used on Space Shuttle Orbital Menuvering engines and the Apollo's Command Module SPS orbital menuvering engine.) The Earliest liquid-fuelled rockets ran on Alcohol or Hydrogen peroxide. Solid Rockets run on ammonium perchlorate, though that's certainly not the only option. By far, in terms of performance, LOX/LH2 is the best oxidizer/fuel combination. In terms of price efficiency... Maybe, maybe not. I don't know and I don't know if anyone knows. If someone knew then I assume every engine would use one or the other, but some engines use one and some engines use the other. LOX/RP-1 has lower performance but is much easier to handle and work with, hence, cheaper. Though because it has lower performance it requires a bigger rocket with more fuel.

I'm sorry, but buzzwords annoy me, and with the whole "green" movement going on, "Oil-based society" and "energy stoneage" really seem more political than scientific.

Now, to reply, we don't use "oil" as our energy reservoir in rockets. Only a very specific fuel out of many different options available use oil, and there's no reason to think of hydrocarbons as low-tech. They're a readily available, cheap, abundant, efficient and portable source of power. Though you're right in that they don't provide as much power as we'd like, though we could always want more power, though spaceflight is very demanding.

Sorry, I'll let Two-Fish answer now...

Thanks for the reply.

I didn't mean to generalize oil as the only source of energy, I was simply trying to point out that the "laws of physics" don't prevent us from overcoming current limitations that we may have.

In terms of the word "energy stoneage", I qualify that with the point that the energy "age" is rather young in our history and for the most part we are at the start of it. I imagine in another hundred years we will look back at the energy "stoneage" just like we look back at the tractors that use oxen to operate.

Also I never mentioned any "green" forms of energy. Personally I think things like biofuels are a joke.

Also what is wrong with "oil based society"? Most of the energy we need comes from oil. Fair enough it doesn't power space vehicles leaving earth, but it damn well powers most of the stuff right here on earth. How the hell is that a buzzword? There are reasons why countries guard their oil and why wars are fought over resources.

Also the truth is that even with technological developments in utilizing oil in more effecient ways, most of the energy in your typical car engine is wasted.

The nuclear fission methods and hopefully the fusion methods is kinda what I'm getting at. Truly in the context of energy with reference to "traditional" forms of energy, you can see the kind of context of talking about when I remark about the "energy stone-age".

 

[twofish-quant]

I think it was the entire Communist-flavored iteration of Marxism that killed the economies of Russia and China, but I'm sure we're diametrically opposed on this point.

Which part of Marxism? Russia in 1950 had state-owned enterprise reacting to centrally planned resource allocations. The US had private enterprises reacting to market prices. Is the problem the state ownership or the centrally planned resource allocations or something else?

Personally, I think that it's the centrally planned resource allocations, which means that you can avoid the problems if you have market prices, even if the corporations are state owned. Which has been the experience of China.

I was talking about physics. Is it actually more efficient in terms of energy? There's an incredible amount of friction from the atmosphere when you plow straight through it at those tremendous speeds. Still, you would have to do a lot of work against the gravitational force with the air-breathers.

The thing about rockets is that you don't have high speeds until you get out of the atmosphere. By the time you are at Mach 10, you pretty much already in a vacuum, which means that you don't have to worry about hypersonic aerodynamics.

 

[twofish-quant]

I was simply trying to point out that the "laws of physics" don't prevent us from overcoming current limitations that we may have.

In what? There are no energy limitations that I can think of in generating a mass consumption society, but we are talking about getting payload into LEO, and in that case you are running against some pretty fundamental constraints. You can think of ways around those constraints, but you can't ignore them.

Also what is wrong with "oil based society"?

The problem is that the supply of crude oil is finite. We've already used all of the "easy oil". We are just going to have to find something else in the next fifty years. No real choice in that. The good news is that there are huge amounts of coal lying around, and if we can figure out a way of having coal power a car, we are set, and we are really close to that. (Burn the coal in power plant, have said power plant power a battery.)

Coal will last us for a few more hundred years, which is enough time to get solar power satellites up, and that will last us until the sun burns out.

 

[D H]

In TEN YEARS, we went from no human having ever gone into space, to landing on the moon. Just two years before that decade, 1957, the first satellite went in orbit. Twelve years before then, the first intercontinental missiles were launched from Peenemünde, the V-2's at Great Britain.

Just because some things were easy in retrospect does not mean everything is easy. You are doing exactly the same thing here as people who say "if we could put a man on the Moon we should be able to do X" (substitute favorite pet project for "X").

I never want to hear "pipe dream" again. All it takes is willpower.

All of the wishing, willpower, and money in the world do not make an idea that is inherently unfeasible, impractical, or uneconomical suddenly become feasible, practical, and economical.

But this is what gets me. Ablative heat shields have survived re-entry on JUPITER at 230 G's, I hardly see how we can't handle mach 4 even at sea level.

The Galileo atmospheric probe was a capsule. It wasn't even a lifting body like the X-38 or SpaceDev's proposed Dream Chaser or Orbital Science's proposed Prometheus vehicle. Even the Shuttle (a delta wing) enters the atmosphere more like a lifting body than like a jet.

Heating of the nose in a hypersonic vehicle is a huge problem. The nose on the X-51 will get up to 1480 °C, and that is for a vehicle whose top speed is "only" Mach 6 (orbital speed is Mach 25). The Shuttle, along with those lifting body reentry vehicles, solve this problem by flying belly-first rather than pointy-end first. This solves two problems: Dumping excess speed, and avoiding having the nose melt off. That is not an option for a vehicle that intentionally flies pointy-end first.

Specific Impulse of 20,000-40,000

Whoa there! what units (is this 20,000-40,000 ft/sec?), and what speed (Isp for an air-breathing vehicle decreases markedly with speed).

After all, we did land on the moon...

Stop that.

 

[Shackleford]

In what? There are no energy limitations that I can think of in generating a mass consumption society, but we are talking about getting payload into LEO, and in that case you are running against some pretty fundamental constraints. You can think of ways around those constraints, but you can't ignore them.
The problem is that the supply of crude oil is finite. We've already used all of the "easy oil". We are just going to have to find something else in the next fifty years. No real choice in that. The good news is that there are huge amounts of coal lying around, and if we can figure out a way of having coal power a car, we are set, and we are really close to that. (Burn the coal in power plant, have said power plant power a battery.)

Coal will last us for a few more hundred years, which is enough time to get solar power satellites up, and that will last us until the sun burns out.

I thought they don't know exactly how crude is formed, that it might not be a "fossil" fuel but rather formed through some other geologic process. It seems to me that the rock cycle would recycle many desirable minerals and possibly even generate crude somehow. If not, they don't know how much crude is actually out there. You don't know if we've used up all the "easy oil." Also, that's the thing - technology dictates what is "easy."

http://www.chron.com/disp/story.mpl/ap/business/7420991.html

D H,

I'm curious. What's your background?

 

[D H]

I tend to agree with you, but in the interests of giving astrophysicists who hate manned space program a far hearing then...

1) A lot of the animus is not directed at manned space flight in general, but specifically project Constellation.

There was a lot of animus within the human spaceflight community against Constellation: Against NASA headquarters for a perceived railroading through of what some thought was a poor design, against Bush for underfunding the program, and against Congress for micromanaging the program and dictating suboptimal approaches.

That said, Bush's initial Vision for Space Exploration concept to get back in the business of sending people beyond low Earth orbit, along with the shift in policy direction from space science back to human spaceflight, was widely perceived in a very positive light throughout the human spaceflight community. "About @#$% time" was the general consensus.

Conversely, I don't know of any astrophysicist that is against the SpaceX program. The reason being is that if that program falls apart it's not going to have any impact on unmanned spacecraft .

They need to rethink that posture for at least two reasons. One is that in the minds of many of the politicians who ultimately fund the space program, the justification for doing space science is that this space science is a precursor for human space activities. The other is that they are looking at the wrong thing. They are doing science, so they should look at how expensive their pet projects are compared to other science programs. Space science comes up very short in this regard. It is very expensive and has a limited return on investment. It is a vibrant human spaceflight program that justifies those expenses.

Astrophysicists aren't experts at politics.

Politics isn't rocket science. It's harder. That's why rocket scientists (and astrophysicists) make such lousy politicians.

Personally, I don't think that you can come up with an argument that makes astrophysicists strong supporters of manned space flight.

They should read history lest they be doomed to repeating it.

 

[elfboy]

nasa is the only hope for space discovery
private sector lacks the funding, safety standards

 

[MattRob]

Thanks for the reply.

[...]

Also what is wrong with "oil based society"? Most of the energy we need comes from oil. Fair enough it doesn't power space vehicles leaving earth, but it damn well powers most of the stuff right here on earth. How the hell is that a buzzword? There are reasons why countries guard their oil and why wars are fought over resources.

[...]

Ah. There's nothing really wrong or that I disagree with in that post. I was under the incorrect impression you were mixing science and politics, but now I see you weren't. Sorry 'bout that. Speaking of mixing science and politics, a major pet peeve of mine (or more specifically, bending science to match political goals)...

So if you disagree with twofish, what feature of communism was it that killed the economies then? Because you do realize he did mention one such feature of the "communist-flavored iteration of Marxism", right? You seem to be just tossing the word around without any substance behind your "arguments", and I find it very odd that people in this day and age still see the world as "red" and the rest. I guess the conservative US propaganda really does still hold sway over the fears of Americans.

I really don't think this belongs in this conversation. I've got quiet a number of strong words against it but this isn't the place for that, let's try to stay on-topic and not rail out against other political views we disagree with or call names...
That's the nice thing about science. At least it tries to be objective, and usually it is very much so.

So, about what I said earlier, is there any fundamental or economic reason why first stage rocket boosters can't be designed more like aircraft? The extremely high Specific Impulse of airbreathing engines should mean that it wouldn't be too hard to have turbofan engines, wings, and minimalistic fuel to return to a landing strip. Sure upfront costs on development and vehicle construction would be high because it's unconventional, but if the goal is to make spaceflight more routine like air flight, why not make it more like air flight? Rocket planes have been around since the early 1940's, at least. (To be fair, with not nearly the Delta-V of any space lift 1st stage boosters...) Why not use a mothership / child aircraft ( spacecraft ) configuration, which has existed since, also, at least WWII. These technologies, unlike current conventional designs, don't require some of the huge logistics or maintenance, though they've certainly had the test of time. Ask any engineer at Virgin Galactic.
Less Logistics and maintenance means shorter turnaround time. Shorter turnaround time means more routine flight, lower prices, and all the goodies that brings.

I've heard it mentioned a few times that rockets are better because they punch through the atmosphere faster. But what if the turbofan engine could be the primary propulsion until it climbs to a high altitude? The mass ratio for a turbofan to climb to ~30,000 feet and later to return to the airstrip would be insignificant, almost. Not to mention a majority of the jet fuel would be used to reach that initial altitude, so it's not there to weigh down the rocket when it fires it's real engines, rockets, whatever kind they be.

Then there's the case of getting an effective mass ratio out of an aircraft design. The shuttle should've proved that's possible, by maintaining a mass ratio of ~6.4 (without SRB's, with ET). External tanks being a technology that has also been around since WWII. I suspect complexity and price of External Tanks could be greatly reduced if they didn't have to hold Liquid Hydrogen. Though that would necessitate a high ~7 mass ratio for each stage, meanwhile LOX/LH2 would only require something around 3.7 - and get this: The Boeing 747 has a mass ratio of 2! 3.7 would really be something...

EDIT: @ D H, Ah, that's meters/second, those are theoretical maximums as opposed to current designs. Current rockets are about at the theoretical maximum of their performance, so perhaps it's not totally unreasonable to suspect scramjets could reach their theoretical maximum within a few decades. And why not remember we did what was impractical, unfeasible, and uneconomic? I think more of the problem with shabby ideas is some being proposed more for an individuals' personal gain or from a business perspective are mixed in with real, objective scientific ideas.

 

[D H]

So, about what I said earlier, is there any fundamental or economic reason why first stage rocket boosters can't be designed more like aircraft? The extremely high Specific Impulse of airbreathing engines should mean that it wouldn't be too hard to have turbofan engines, wings, and minimalistic fuel to return to a landing strip.

Economics. Specific impulse is not the right metric. For the most part the only metrics that count are how big (payload mass to orbit) and and how much (dollars per unit payload mass).

There are exceptions. For example, Orbital Sciences uses its aircraft-launched Pegasus rocket to launch small payloads into space at a high cost per unit mass. This becomes economical for a small payload when the options are to pay full fare on a larger launch vehicle or piggyback as a secondary payload on the launch of a large payload and get into a suboptimal orbit. These exceptions for the most part pertain to small payloads. The goal here is presumably to get large amounts of mass into orbit as cheaply as possible.

High specific impulse is not the be-all and end-all toward achieving this goal. There is a lot to be said for the cheaper, low-tech technologies that have been built for decades. This won't be the case forever, but it certainly will be for at least the next ten years, minimum (and twenty is a better bet).

Ask any engineer at Virgin Galactic.

Ask them what? Virgin Galactic's current plans are to offer sub-orbital flights only. Getting something into orbit is orders of magnitude harder than what Rutan did to win the Ansari X Prize. Virgin Galactic hopes to offer orbital flights someday, but when and how are not specified.

EDIT: @ D H, Ah, that's meters/second, those are theoretical maximums as opposed to current designs.

I figured out what the units were. One of the most common mistakes made by students here (and presumably elsewhere) is ignoring units. That said, those numbers are for low speed only. Look at the chart in post #97. Specific impulse drops markedly with increased velocity. That "theoretical maximum" curve? That's for an engine exhausting into vacuum and with an exhaust temperature of 0K.

-------------------------------------------------------------------

I have no problem with doing R&D into future propulsion technologies. NASA and the Air Force should be doing R&D on lots of different propulsion technologies. You should not take me as a naysayer here. What I do have a problem with is prematurely picking some immature technology as the winner, particularly when that decision is made on political connectivity rather than technical merit. Scramjets are one of those. The amounts of money [strike]spent[/strike] wasted on this technology because it has a lot of political backing is immense. Tens of billions were spent on it with the National Aero-Space Plane program alone.

 

[twofish-quant]

I thought they don't know exactly how crude is formed, that it might not be a "fossil" fuel but rather formed through some other geologic process.

There are people that believe that crude oil is produced by non-fossil processes. Most people in the industry believe that these people are "crackpots."

If not, they don't know how much crude is actually out there.

We have a pretty good idea.

You don't know if we've used up all the "easy oil." Also, that's the thing - technology dictates what is "easy."

"Easy oil" is oil that you can get without technology. We've already run out of that. In the 1930's, you could dig a oil in East Texas, and the oil would just gush out.

That oil is gone. You can do the "dig the oil and collect oil" in Saudi Arabia, but that's going to be gone in the next twenty to thirty years. At that point you have to invest in technology in order to get the oil, and technology is expensive, so we are already at the point that we are spending more and more money to get less and less energy. A Gulf oil platform costs a $1 billion.

The good news is that this creates a lot of good paying jobs for astrophysicists. Also, the good news is that once the oil disappears, it will be an annoyance rather than a giant crash (at least in the US.)

 

[twofish-quant]

Ah. There's nothing really wrong or that I disagree with in that post. I was under the incorrect impression you were mixing science and politics, but now I see you weren't.

I am mixing science and politics. There's no way that you can deal with issues like the space program without mixing science, politics, and economics.

So, about what I said earlier, is there any fundamental or economic reason why first stage rocket boosters can't be designed more like aircraft?

DH has gone through them. People have tried doing it for the last fifty years. So far nothing that is ready for prime time. We should still look for them, but it's nothing that you can take to the bank right now.

And I use "take to the bank right now" in a literal sense. When Boeing needs more money to build the 787, they can go to Wall Street and get money from investors. The important thing about this is that Boeing (or for that matter SpaceX) is dealing with reasonably mature technology, and you can put the numbers in a powerpoint and give it to Wall Street investors, and then argue that there is a reasonable chance that they will make money off the deal.

You can't do that with airbreathing engines right now. Because you can't, you have to rely on government funding, and once you do that, you can't go "lean and mean." If you pour government money into basic research, then in ten years, you might be able to make that presentation to investors, but you can't right now.

But what if the turbofan engine could be the primary propulsion until it climbs to a high altitude? The mass ratio for a turbofan to climb to ~30,000 feet and later to return to the airstrip would be insignificant, almost.

It's not. Airplanes are flying fuel tanks. They can get away with a lot because they don't have to carry oxidizers. The problem is that getting you to mach 0.9 at 6 miles is is pretty insignificant for getting you to mach 25 at 100 miles.

Not to mention a majority of the jet fuel would be used to reach that initial altitude, so it's not there to weigh down the rocket when it fires it's real engines, rockets, whatever kind they be.

Kinetic energy goes v^2. The kinetic energy that you get from a jet aircraft is pretty insignificant and you are then limited by the payload of the jet.

I suspect complexity and price of External Tanks could be greatly reduced if they didn't have to hold Liquid Hydrogen.

If you are holding liquid oxygen, then you have to deal with cryogenic fuels. You can deal with room temperature fuels but those don't have the energy content.

Current rockets are about at the theoretical maximum of their performance, so perhaps it's not totally unreasonable to suspect scramjets could reach their theoretical maximum within a few decades.

If we are talking 2050, then all bets are off. It could be that in 2025, someone figures out a way of making massive amounts of carbon nano-tubes that let's us make space elevators. The discussion here is 2015-2020, and scram-jets are not ready for prime time. If we put money in them then by 2020, we could use them in discussing plans for 2030, or we can find that they just don't work. Scram-jets (and carbon nano-tubes) are disruptive technologies, and those technologies you just can't count on for near term planning.

And why not remember we did what was impractical, unfeasible, and uneconomic?

Because you are looking at the horse from the wrong end.

A 12-year old from 2050 could save me a huge amount of time because they know what technologies worked and which ones didn't. From 2011, we know that rockets work and nuclear airplanes and zip fuels didn't, and that the future was in jumbo jets and not SST's. If you look at people in 1965 with the knowledge of 2011, then of course they were idiots because they were making guesses that ended up being wrong.

I am certain that there is a technology that "couldn't possible work" that will. Unfortunately, I have no idea which of the hundreds of technologies that is. If you put all your money on scram-jets, then that means less money in laser powered rockets, solar sails, carbon nano-tubes, and battery technology.

I think more of the problem with shabby ideas is some being proposed more for an individuals' personal gain or from a business perspective are mixed in with real, objective scientific ideas.

If you ask me the problem with Communism is that they assumed that people would act in different ways than they actually do. *OF COURSE* people will act for personal gain.

If you assume that people don't act for personal gain, you'll end up with a political and economic system that just doesn't work. There are no-doubt people that are self-sacrificing, but people that aren't in it for personal gain, rarely end up in positions of major political or economic power, because they are nice and get eliminated by people that are hungry.

Politicians want votes. Business people want money. Workers want bread and circuses, and scientists (being human) aren't more self-sacrificing than anyone else. Your typical scientist wants funding and glory so that they can papers written. If you get a group of senior scientists together, they'll start gossiping like old women about how they are trying to get funding for their university, and also who is "in" and who is "out".

The problem of getting people to the LEO or the moon is not a scientific problem. We've done it before. It's a business/political problem.

 

[twofish-quant]

"About @#$% time" was the general consensus.

The problem is getting money.

Personally, I don't think that anything will happen until it appears likely that there are going to be red flags spread across the solar system.

They need to rethink that posture for at least two reasons. One is that in the minds of many of the politicians who ultimately fund the space program, the justification for doing space science is that this space science is a precursor for human space activities.

The other thing about manned space programs is that they provide a huge amount of pork. More so than unmanned space programs. Ultimately politicians care about votes and jobs, and scientific research doesn't *directly* produce much of that.

Curiously, Chinese politicians are as scared about votes and jobs as American ones. Chinese politicians don't have to worry about being voted out of office, but they are terrified at the prospect of losing power in a way that is less nice (see Egypt). Ultimately the way that you stay in power is "bread and circuses" and the Chinese government uses its manned space program as part of the circuses part of the equation. And if you can keep someone so busy at work that they don't have time to attend a protest, even better...

They are doing science, so they should look at how expensive their pet projects are compared to other science programs. Space science comes up very short in this regard. It is very expensive and has a limited return on investment. It is a vibrant human spaceflight program that justifies those expenses.

And then you ask what justifies human spaceflight, and my answer is the "college football" argument. If we can get things so that people get into a competition to plant flags in the solar system, I think we'll be a lot better off as a species. People seriously lost interest in manned space flight around the time it became obvious that the US "won."

Politics isn't rocket science. It's harder. That's why rocket scientists (and astrophysicists) make such lousy politicians.

Sometimes. There's nothing that makes an astrophysicist a good politician, but there is also no particular reason an astrophysicist would make a worse politician than a lawyer or CEO. If you had more physics Ph.D.'s that went to work as lobbyists, I think we'd be

They should read history lest they be doomed to repeating it.

The problem is that people have wildly different points of view of history.