We Stopped Dreaming

[luke strawwalker]

Didn't they bring small nuclear heaters on the Apollo missions? and some other flights used them also.

Now we just need ''BIGGER''!

I got sidetracked with stuff here in the house before I finished my post, but yeah, they used RTG's on Apollo...

In fact, the RTG they carried on Apollo 13 reentered with the Aquarius LM (which followed a reentry path similar to what an SM ordinarily would, reentering and burning up a couple hundred miles away from the CM's reentry corridor and splashing down in the Pacific.) The LM of course shredded into a million pieces upon entry interface, most of which probably burned up or dropped into the Pacific shortly thereafter, while the RTG survived reentry and dropped intact into the Pacific and sank intact... just as it was designed to do.

Of course, designing a nuclear powered engine large enough to PROPEL a MANNED vehicle, meaning an ACTIVE FISSION POWERED REACTOR, would be very difficult. There was a huge outcry even for using the NERVA engine on the S-IVB stage, essentially in the uppermost regions of Earth's atmosphere after 95% of the ascent had been performed. Using one for liftoff from the Earth's surface is a guaranteed non-starter... heck even if you invented fusion impulse drive, which theoretically at least would not be producing much radiation (strictly direct line-of-sight radiation from the fusion process itself-- no residual heavy isotope "fallout") you'd STILL have an ENORMOUS fight with the greenies and evirowhackos and "if it's nuclear it means the end of all life on Earth" crowds...

But, of course we cannot even create self-sustaining net-energy positive fusion for commercial power on Earth, which is a HUGE way from designing a flight-capable propulsion system! Maybe in a century or two...

While nuclear thermal propulsion makes a lot of sense for in-space applications such as going to Mars (and makes such a trip INFINITELY easier) it's not going to be an answer to lifting stuff from Earth's surface into space for a century or more... if ever...

later! OL JR

[DeanHFox]

I know the technology has INCREDIBLE issues to overcome, but I've always been fascinated by the magnetic linear launcher. I first read about one in Heinlein's "Man Who Sold the Moon", and later in his novel "The Moon is a Harsh Mistress" (although that magnetic catapult was on the airless lunar surface).

Maybe someone's taking the idea seriously --- see http://www.launchpnt.com/portfolio/a...e-launch-ring/

The other technology I always thought was thought-provoking was the "laser-power launcher", in which a ground-based laser heats the air immediately underneath a specially-designed capsule so that the air rapidly expands and is thrusted out from beneath the capsule. The laser "pulses" (zap, thrust, zap, thrust) to punch the capsule upward. The "Star Wars" program even tested such a lightcraft (cool video at http://science.howstuffworks.com/light-propulsion1.htm). Jerry Pournelle used this launch method in his novel, "High Justice".

Just a couple random thoughts.

[boomtube]

If I’m not mistaken the “Laser powered launcher” actually used a shield that was layered with some materiel that was vaporized by the laser pulse turning from a solid directly to a plasma.

It was this reaction that provided thrust. Each laser pulse vaporized each successive layer until orbit was achieved.

Another idea was a system to discharge a colored /dyed water vapor into the “Combustion chamber” just before each laser pulse.

Look up the expansion ratio of water into steam and you’ll understand why this would work so well.

The problem with a laser powered LEO vehicle is both throughput of developed lasers being far too low and the absorption of the laser’s energy by the atmosphere.

Using multiple lasers could get around the first problem but then you have to deal with keeping multiple beams synchronized and on target.

[luke strawwalker]

If I’m not mistaken the “Laser powered launcher” actually used a shield that was layered with some materiel that was vaporized by the laser pulse turning from a solid directly to a plasma.

It was this reaction that provided thrust. Each laser pulse vaporized each successive layer until orbit was achieved.

Another idea was a system to discharge a colored /dyed water vapor into the “Combustion chamber” just before each laser pulse.

Look up the expansion ratio of water into steam and you’ll understand why this would work so well.

The problem with a laser powered LEO vehicle is both throughput of developed lasers being far too low and the absorption of the laser’s energy by the atmosphere.

Using multiple lasers could get around the first problem but then you have to deal with keeping multiple beams synchronized and on target.

Yeah, PERFECTLY aimed at all times...

Otherwise you vaporize your spacecraft or perforate it with a laser beam! Besides, the weight has to be EXTREMELY low for this to work at the scales that we could reasonably build... No way I can see this working for a manned spacecraft, which is inherently going to be big and weigh TONS...

We can miniaturize everything but humans... LOL

Later! OL JR

[bobkrech]

I know the technology has INCREDIBLE issues to overcome, but I've always been fascinated by the magnetic linear launcher. I first read about one in Heinlein's "Man Who Sold the Moon", and later in his novel "The Moon is a Harsh Mistress" (although that magnetic catapult was on the airless lunar surface).

Maybe someone's taking the idea seriously --- see http://www.launchpnt.com/portfolio/a...e-launch-ring/

The other technology I always thought was thought-provoking was the "laser-power launcher", in which a ground-based laser heats the air immediately underneath a specially-designed capsule so that the air rapidly expands and is thrusted out from beneath the capsule. The laser "pulses" (zap, thrust, zap, thrust) to punch the capsule upward. The "Star Wars" program even tested such a lightcraft (cool video at http://science.howstuffworks.com/light-propulsion1.htm). Jerry Pournelle used this launch method in his novel, "High Justice".

Just a couple random thoughts.

The magnetic launch concept is BS. The projectile has to be moving at ~11 kms leaving the launcher to make it to orbit. There are several problems.

1. Moving horizontally in the lower atmosphere at ~11 kms would vaporize the projectile surface in fraction of a second. This fact is poo-pooed by just about anyone who proposes this type of system

2. The sonic boom would be deafening.

3. The acceleration of a projectile moving around the circular track would destroy most payloads.

4. This concept is simply a gun-launch to orbit without the gun.

http://alnaspaceprogram.org/index.html is a semi-pros attempt to investigate some of these concepts.

http://www.astronautix.com/fam/gunnched.htm is an interesting history of past gun launch attempts.

If I’m not mistaken the “Laser powered launcher” actually used a shield that was layered with some materiel that was vaporized by the laser pulse turning from a solid directly to a plasma.

It was this reaction that provided thrust. Each laser pulse vaporized each successive layer until orbit was achieved.

Another idea was a system to discharge a colored /dyed water vapor into the “Combustion chamber” just before each laser pulse.

Look up the expansion ratio of water into steam and you’ll understand why this would work so well.

The problem with a laser powered LEO vehicle is both throughput of developed lasers being far too low and the absorption of the laser’s energy by the atmosphere.

Using multiple lasers could get around the first problem but then you have to deal with keeping multiple beams synchronized and on target.

As someone involved in laser rocket propulsion and technology spin offs for the past 35 years, I can comment with authority on the subject.

0.) Laser heated rocket thrusters were first proposed by Authur Kantrowitz at Avco Everett Research Laboratory circa 1972. My company Physical Sciences Inc. was started in 1975 by former Avco employees and continued theoretical and experimental reseach in both pulsed and CW laser heated rocket thrusters. The first experiments producing in excess of 3000 s specific impulse with hydrogen were conducted at PSi circa 1977 by Peter Nebolsine, and the first successful development of CW laser heated rocket propellants utilizing molecular absorption were conducted circa 1980 at PSI by me. Leik Myrabo, a friend and fellow co-worker, worked for Peter and developed the Light Craft concept at PSI in the late 70s before he went to RPI.

1.) Where's the laser?

There aren't any large enough to do the job, and none on the drawing board. The largest lasers are megawatt class lasers (average power). To launch a small payload into orbit you need several hundred megawatt class lasers gigawatt class lasers for moderate payload capability. A gigawatt average power laser needs at least 2 GW of electrical power to operate assuming 50% efficiency.

2.) There are 2 generic types of lasers: pulsed and CW; so there are 2 types of laser rocket motors: pulsed laser rocket thrusters and CW laser heated rocket thrusters.

a. Pulsed laser heated rocket thrusters either

1.) ignite a plasma in a gas that absorbs the energy via inverse Bremssralung processes and the expanding plasma drives a LSD wave (Laser Supported Detonation ) hrough the cold gas ahead of it, heating it and accelerating it to a high velocity, several times higher than is possible by a chemical reaction. Hydrogen is the most effieicnt fuel with a demonstrated specific impuilse of 3000 s. Air has also been used and is the propellant used in LightCraft. In 1985 I co-developed and later patented a process using LSD waves to heat oxygen gas and produce atomic oxygen flows tunable from 5 to 15 kms for ground based studies of the chemical environment around spacecraft in low earth orbit. It is the current gold standard for LEO simulation facilities wordwide, and is the only known practical and commercial use of pulse laser heated rocket thruster technology.

2.) ablate a solid into the gas phase generating a high velocity flow. Unless the ablation products are low molecular weight such as hydrogen or water, the process is not efficient.

b.) CW laser heated rocket thrusters either by

1.) ignite a plasma in a gas that abosrbs the laser energy via inverse bremstrallung in in an LSC wave (Laser Supported Combustion) wave process. This doesn't work because the high density 10,000+ K plasma opens up the nozzle throat and reduce the exhaust velocity to not more than ~5 kms (500 s) in practical designs.

2.) continuous heating propellant via resonant molecular absorption and collisional energy tranfer to hydrogen. I demonstrated this concept experiemrntally in the early 80's and developed a hydrogen gas based propellant with 10% water and 1% NH3 that would operate with a specific impulse > 1000 s at temperatures below 3500K.

Atmospheric transmission is not a serious problem if the lasers are positioned in deserts or on mountain tops, however as previously stated, no existing lasers are big enough to power an operation laser powered rocket, and the technology to buid them does not exist.

Bob

[gdjsky01]

I am not going to comment on the taxes, or politics. Nor cold wars and holy wars. No matter what I post, or you post, no matter how long, is not going to explain the complexity of situation. Its not that simple even if some may believe it is.

I will not let the word postmodernism go without a clear understanding (because I HATE the whole idea of it).

WARNING:

Postmodernism is, in part, the Oprah idea of everything can't be known. That science and naturalism have it wrong and that you can influence the physical world by wanting it so. "The Secret" is an an example of post modernist hogwash. Widespread belief in psuedo-science and alt-med is postmodernism.

Wikipedia (with my highlighting):
Postmodernist approaches are critical of the possibility of objective knowledge of the real world, and consider the ways in which social dynamics such as power and hierarchy affect human conceptualizations of the world to have important effects on the way knowledge is constructed and used. In contrast to the modernist paradigm, postmodernist thought often emphasize idealism, constructivism, relativism, pluralism and scepticism in its approaches to knowledge and understanding.

Note the common usage of scepticism. Scepticism in postmodernism means sceptical of any claim to concrete knowledge. And see the weasel words (IMO) of relativism, pluralism. Meaning your idea of reality is as good as mine. Isaac Asimov had great quote that IMO refutes this:

There is a cult of ignorance in the United States, and there always has been. Anti-intellectualism has been a constant thread winding its way through our political and cultural life, nurtured by the false notion that democracy means that 'my ignorance is just as good as your knowledge.'

Scientific skepticism, which is what I identify with and try to practice, understands knowledge of the real-world is objective and can be known completely (even if incomplete at this time) via empirical methods. And I see science as a way forward. Even with all it's missteps - it is after all a human endeavor and we are flawed animals, IMO science delivers the goods.

[BABAR]

Just to restir the hornet's nest:

What is the point of continued manned exploration in th intermediate (say 50 years or two generations) future? This puts it in the range of vision of the (vanishing) middle class--"what is in it for my kids or my grandkids?" Note this is still a huge stride compared to the American political time frame, which must demonstrate results in 2, 4, or 6 years depending on whether you are a Congressman, President, or Senator. Kennedy set the goal "by the end of this decade" if memory serves. We rocket junkies may have great motives, we may even be "right" in saying exploration of space is "worth" the cost, but what argument will convince the majority of voters to select political representatives who will either redirect (or increase) tax money to pay for the program?

Interesting comment about public freaking out about "nuclear energy." The science of Magnetic Resonance Imaging (MRI) was based on Nuclear Magnetic Resonance. The "Nuclear" was based on the physics of the atomic nucleus, most commonly the single proton of the hydrogen atom. There was (and isn't and never will be)any IONIZING radiation associated with NMR or MRI. But the word "NUCLEAR" was dropped.

My gut feeling is that the "breakthrough" required (if it occurs) will be the practical development of cheap (REEEEAALLLLY CHEAP) energy. If/when this occurs, it will provide the economic and technical leap to proceed with exploration beyond lunar orbit. The other factor will be population stabilization as the currently lrojected course is to keep breeding until disease, famine, or war act as involuntary population controls.

I know, here come the hornets!

[JStarStar]

Just to restir the hornet's nest:

What is the point of continued manned exploration in th intermediate (say 50 years or two generations) future? This puts it in the range of vision of the (vanishing) middle class--"what is in it for my kids or my grandkids?" Note this is still a huge stride compared to the American political time frame, which must demonstrate results in 2, 4, or 6 years depending on whether you are a Congressman, President, or Senator. Kennedy set the goal "by the end of this decade" if memory serves. We rocket junkies may have great motives, we may even be "right" in saying exploration of space is "worth" the cost, but what argument will convince the majority of voters to select political representatives who will either redirect (or increase) tax money to pay for the program?

That was my point with the tea party picture.

Neil DeGrasse Tyson is a brilliant guy, but he's crazy if he thinks any politician in 2012 America is gonna vote to double the NASA budget, or for that matter increase it 10 cents. They will be beyond lucky if they can maintain anything close to the current levels unless there is an absolute economic boom.

Plus we have a lot of people working on the assumption that anything connected with "science" is foo-foo pencil-neck-geek witch-doctor stuff.

The idea of offering "prizes" for orbital flights, etc etc. ain't gonna work either -- commercial enterprises aren't going to invest the money in the technology unless there is some prospect for payback in the imminent future.

[luke strawwalker]

That was my point with the tea party picture.

Neil DeGrasse Tyson is a brilliant guy, but he's crazy if he thinks any politician in 2012 America is gonna vote to double the NASA budget, or for that matter increase it 10 cents. They will be beyond lucky if they can maintain anything close to the current levels unless there is an absolute economic boom.

Plus we have a lot of people working on the assumption that anything connected with "science" is foo-foo pencil-neck-geek witch-doctor stuff.

The idea of offering "prizes" for orbital flights, etc etc. ain't gonna work either -- commercial enterprises aren't going to invest the money in the technology unless there is some prospect for payback in the imminent future.

Absolutely.... couldn't agree with this post more...

Thing is, NASA's interaction with the Congress/Admininstration(s) is an ongoing greek tragedy... NASA proposes a massive mission for $XX billion dollars. Congress and (usually OR) administration agrees (both have to at least tacitly agree to it, because for things to get funded, the President proposes and the Congress disposes (of the funds). Usually the gov't side of things (IE Congress, though sometimes the President-- Reagan very nearly killed unmanned robotic planetary exploration-- heck they were SO dedicated to "fiscal conservatism" that they nearly killed the Grand Tour after Saturn-- just by "turning off the lights" on the Deep Space Network at Goldstone and elsewhere... Voyager would have sailed on to Uranus and maybe Neptune (in the general vacinity anyway) and transmitted back, but NOBODY on Earth would be listening! All this while Reagan lavished money on DOD and soon proposed "Star Wars" which ran into the billions and would have cost hundreds of billions to actually field...) Anyway, the gubmint boys n girls get cold feet and don't want to pay $XX billion for the program NASA presented them with and they agreed to, so they cut funding to 2/3 of $XX billions or 1/2 of $XX billions and tell NASA to "make do". SO, NASA goes back to the drawing board, makes a few cuts here and there, adds on another couple years or so of development, which adds even more billions to the drawn out program, and then the contractors or the science community or whomever the "stakeholders" in the system are do some lobbying or make their presence felt in Washington, which usually gets Congress in the mood to put their two cents in, forcing MORE redesign or change of emphasis or reinstatement of things NASA decided to cut for lack of funding, forcing MORE redesign and changes, delaying the works more, adding MORE billions in development costs, and then usually things change in the program or in Congress/White House and a new crop of politicians come along, the situation changes or the priorities change or something else happens that generally redirects attention and resources elsewhere, and the project usually ends up canceled or majorly changed until it ends up eventually going through, in a form hardly recognizable to what was proposed at the beginning, with the stink of a dead albatross clinging to it, and ends up YEARS overschedule and costing 2-3 TIMES the original planned budget of $XX billions that the Congress or White House balked at after agreeing to it in the first place...

I don't know how you fix this... The Europeans do things a differently-- they allocate $XX amount of money to a project according to the estimated cost and then break that up according to the projected funding curve, and then provide the necessary funds yearly as the project continues and as they agreed to in the beginning. It's not like the US where every year the program basically has to be voted on to be "continued" via being funded adequately to actually get things done... and where economic downturns or other political pressures can end up cutting into funding, so that a project expecting to get $X billion this year actually ends up getting only half or 1/3 that, which is barely enough to keep the lights on, let alone actually make any progress at completing the milestones in the development or design for that year... Then of course everybody wonders WHY the program ends up getting dragged out and ending up years late in the schedule, and of course the additional years of salaries and operations and design and development end up adding billions to the cost...

It's a vicious cycle. Fix THAT and you're halfway to getting a great space operation going.

Seems like NASA would learn this stuff... but then again, it's simply how the game is played. You play the hand your dealt or push back from the table and call it a day... It seems like NASA would have more to gain by proposing a cheaper, simpler, smaller way of doing a mission and actually getting that funded and actually completing it on time and on budget, rather than the way they do it now, which is propose the "Battlestar Galactica" size/cost/complexity mission and hope Congress will actually fund the "shuttlecraft" size/cost/complexity type of mission... and will actually commit to it and deliver the agreed upon funds. I guess NASA figures that if they propose the "shuttlecraft" class mission expecting it to be fully funded, they won't even get that... that WHATEVER they end up proposing will, regardless of it being a less expensive option or not, will end up being underfunded and cut back (downscoped) and drawn out in cost and schedule anyway, so why not simply propose the Battlestar Galactica in the first place so you end up with the shuttlecraft in the end anyway, even by the tortuous roundabout route that ends up costing twice as much and taking twice as long anyway...

It is a MESS... BUT, it's the government's preferred way of doing business!

Later! OL JR