Slashdot Mirror
NASA Eyes Shuttle Replacements
jonerik writes "According to this article at Space.com, NASA yesterday released a status report on the first year of NASA's Space Launch Initiative; the search for a space shuttle replacement, currently planned to begin operating ten years from now. The competing contractors - Boeing, Lockheed Martin, and a team consisting of Northrop Grumman and Orbital Sciences Corp. - have their work cut out for them. NASA is looking for both a ten-fold improvement in per-pound launch costs (from $10,000 per pound to $1,000) and massive improvements in crew survivability."
In related news, Rubyflame writes: "Aviation Now has a
story about four new kerosene-fueled rocket engines being developed by Aerojet, Pratt & Whitney, Rocketdyne, and TRW. These are engines that will produce a million pounds of thrust, intended to outdo Russian designs in reliability and launch cost, and one of them may power a new reusable launch vehicle. Kerosene has the advantage that it's denser than hydrogen, so the fuel tanks can be smaller."
Nasa space shuttle
Takes off like a pile of bricks
Lighter craft required
This article is light on details but does mention that all of these systems that they are working on are two-staged.
:-)
At first you may think that two-staged launches are a waste of money, but some of it does at least look promising.
The design from Boeing is an interesting one. It looks like a smaller shuttle attached to a jumbo jet. It's then flown near the limits of space where the top ship would then come apart and finish it's journey into space on it's own.
The jumbo jet would then return to the launch site.
I must admit that I would love to see a 1 stage space craft.
Now, I am coming from a background where I am not incredibly familiar with either U.S. capitalism or with issues of defense. Basically, there are a handful of these companies that compete for every government contract. To maintain "competition," the government will try to spread the love around, going with different companies for succesive contracts.
But each individual contract is too big for a single company to fulfill on its own, so whomever ends up winning the contract will turn around and outsource some of the work to...the same "competitors" whose bids they beat out!
As a retired rocketman, I am the first to support expansion and improvement of any nation's space program. I just wanted to point out that the notion of "who will build the next generation shuttle" should be taken with a grain of salt.
"I'm a rocket man / Rocket man burning out his fuse up here alone." - Sir Elton John
"Rockhound: You know we're sitting on four million pounds of fuel, one nuclear weapon and a thing that has 270,000 moving parts built by the lowest bidder. Makes you feel good, doesn't it?"
hehe...
Fore more quotes from that movie go here
My $0.02 will always be worth more than your â0.02, so
They just want gobs of money to spend on technology development programs (read "new toys").
American tax dollars are working to make these "new toys". The primary justification for NASA's funding is that the technologies that come out of these "technology development programs" push the cutting edge of modern tech.
It's been a long time since Congress has thought about the values of "exploring space". That's just an side-effect of research spending.
It's like those robot-construction competitions where they have to get all the balls into the goal. The contest isn't to designed to solve the great "yellow ball problem", it's to build and explore ideas in technology.
Congress views funding NASA the same way; by funding NASA they're advancing America's technical know-how. Not to mention that NASA contracts go to high-tech american industries.
There's not some sort of conspiracy to keep regular people out of space here. NASA's just doing its job.
Sweat
It breaks my pluginses, my precious!
Problem was the Saturn 5 was already paid for (million pound thrust kerosene engine -- didn't they call than the F-1?) while the Shuttle that replaced it required billions in development cost. Also, the Saturn could put 4 times the payload in LEO, making it half as expensive as the Shuttle per pound, and it could send stuff to the Moon.
Instead of punching around with the Shuttle in LEO and this Space Station which is the overpriced whatever, we could have kept Apollo going and evolving, and with the same money we have spent, we could have had a permanent human presence on the Moon by now.
What would that gain? Well, we could have a much more thorough evaluation of lunar resources (possible polar ice) and more thoroughly evaluated O'Neil's ideas of using the Moon as a source of construction materials for space-solar beamed power systems in geosynchronous or L-whatever orbits. Instead we are dinking around in LEO learning nothing.
The Big Dumb Booster by the way, was an idea to scale up the Lunar Module descent engine (had to be a KISS design to bring the astronouts down in one piece) -- they gave the job of building a prototype motor to some general construction contractors who didn't know the first thing about rockets, and they test-fired a successful motor. The thing would have been the size of a Saturn but much more cheaply (heavily) build -- payload would have been more in the Shuttle category, but the idea is that boiler and bridge makers could slap them together. Of course the Shuttle killed the idea.
Aside from Challenger?
Please note that during the first 2.5 minutes of every shuttle launch, there are NO abort modes that are survivable. If there are any problems with the SRBs, they cannot be turned off. If there are any catastrophic problems with the ET, it doesn't matter, you must continue your launch profile until the SRBs have stopped.
Three engine shutdown during SRB burn? Shuttle disintegration.
ET rupture? Shuttle disintegration.
Pretty much anything, dead astronauts.
The russians use 40 year old technology, but at least they have survivable aborts throughout the entire flight profile.
On another article a few weeks back, someone posted an answer that cleared this up for me. (I'm too lazy to track down the posting now.)
Bottom line is: hydrogen is like a high-horsepower, high-RPM turbo racing engine; it's best for driving light vehicles at high speeds (upper stages). Kerosene is like a high-torque diesel truck engine, good for getting a lot of weight moving from a dead stop.
The difference has to do with the physics of exhaust density, speed, momentum, etc.
Its true though that all of the designs share some characteristics...one stage to get you off the gorund, one to get you into orbit. Obviously this isn't by accident...the physics of the problem and materials/fuel presently available must dictate this design.
Because we like to torment you. It obviously bothers you.
I also heard that France was working on a shuttle. Portugal has been flying their shuttle for years, though it's not widely publicized. Mexico scrapped their shuttle project in favor of their rail-gun / light-sail combination system with which they've manage to supply migrant workers for the asparagus farming on Venus.
XML causes global warming.
Who says the 'moon base' has to be made out of metal? Why can't you ship up some excavation tools, and light weight polymers and build an airtight underground lunar base with the only imported metal being the airlock doors? True, this doesn't provide you with any method for creating food, but We Could have had a lunar base easily. One much larger than any of the space stations we've shipped up, because as you recall all of those ARE made out of tons and tons of metal. There is also a cumulative advantage, the longer you've been building stuff on the moon, the more resources are at your disposal to build more complex projects... Unlike the space stations which all fall back to earth after a few decades. Depending on how far we push nanotech we may not even need to build factories on the moon, we may just need to send up a few machines that recieve power wirelessly and process raw materials into usable resources.
The moon is a more practical environment to work in, the low G enables a person to remain there signifigantly longer than in the microgravity of space.
The Biosphere projects are partially aiming at researching the viability of building an enclosed, self sustaining habitat on the moon, but even if you build a moon base that requires resupplying like space stations do, it could easily be done for less money as long as you take advantage of the fact that you can always dig a hole use some plastic to make it airtight and cover it with a metal lid. Homsteaders used to build houses out of earth and mud where trees weren't available, so why should we build lunar bases out of 'industrial grade metal' when really the only part that has to be metal is the door.
https://www.gnu.org/philosophy/free-sw.html
Ground based lasers will always be subject to thermal blooming due to atmospheric attenuation.
Interesting. Is this caused by the lasers or just natural artifacts of the atmosphere? Incidentally power is the cheap bit in the equation, and you need less of it delivered at altitude due to g-limiting anyway; so it may not matter.
Atmospheric. You have two effects happening. One is that minute particles in the atmosphere scatter the laser beam. This is unavoidable, and causes exponential attenuation over long distances. The second is that the atmosphere absorbs some of the light you're sending, and heats up. This causes optical mayhem that defocuses the beam.
Compounding the problem is the fact that you'll have to fire through a *lot* of atmosphere. Your craft needs most of its velocity to be tangential, and you want as long an acceleration path as you can get away with to keep the acceleration to something that a) you can provide and b) won't damage your cargo. This means a grazing path through the atmosphere, which means your lasers will be firing through hundreds or possibly thousands of kilometres of air (i.e. as far as you can manage).
The only practical scheme I can think of for very long distances is to have multiple stations along the flight path and to fire a converging beam, so that heating problems are only significant for the last little part of the beam path.
On a couple of other points: You'll be using a laser array, not a single laser, so the cost will be directly proportional to the power required. More power means more cost.
Also, I have doubts about a heat-exchanger system working. Throughput tends to be low compared to the power flow required to get high ISP, and a heat exchanger means a heavier craft. The most practical craft design I've seen suggested, which has flown in small-scale tests, has the bottom of the craft being a curved mirror with a central projection. The laser is focused by the mirror and heats air immediately below the central projection, which is shaped to force the air to move away from the craft.
Laser launchers are a neat idea, and avoid the problem of carrying most of your reaction mass when set up in jet mode, but there are formidable engineering problems to overcome before they're practical.