Follow Slashdot stories on Twitter

 



Forgot your password?
typodupeerror
Check out the new SourceForge HTML5 internet speed test! No Flash necessary and runs on all devices. Also, Slashdot's Facebook page has a chat bot now. Message it for stories and more. ×

Comment Re: Who cares? (Score 1) 303

You're assuming that it is a one time operation. here's the long term problem: At best 5% of a launch mass goes to the payload to reach LEO. At best. If launching a manned mission to Mars, the vast majority of the launch fuel will be to get the vehicle to reach LEO. So the vehicle most likely will have to be re-fueled in orbit. Again 5% of a launch just to refuel a craft.

Certainly it can be done short term for a few flights. However a long term mission to Mars might be better off with moon refueling where gravity is 1/6 that of Earth. Will it be easy to set up a Moon base to serve as a refueling point? No. But in the long run it will be better.

Comment Re: Great idea... But there is a problem... (Score 1) 303

aka, for every 10 kg you launch to LEO you get 1kg payload to your destination

That's factually not true. Falcon Heavy Weight (1,420,788 kg), LEO payload (54,400 kg ): 3.83%
Ariane 5 Weight: 777,000kg, LEO payload: 16,000 kg. 2.05%
Atlas V Weight 345,000, LEO payload: 18,810 kg: 5.45%

At best it is 5%. At best. Many orbital launch systems deliver less than 5%.

Just 3000 m/s is a nearly 3:1 ratio.

Someone is forgetting basic physics. F=(1/2)m(v^2). The ratio is not 3:1. The ratio is (10^2)/(3^2) or 11:1.

Comment Re: Great idea... But there is a problem... (Score 1) 303

Because they're... probes? Most of them weigh so little and go by so energy efficient orbits that there's no point.

If their orbits are so efficient why do many of them have flybys so they get a gravity assist? These are also unmanned probes for which time is not as important a factor as a manned mission.

Your typical probe is maybe a ton, the Curiosity mission was a real heavyweight at almost four tons total - of which the rover itself was around one, but still something a regular Falcon 9, Atlas V or Delta IV could deliver to Mars. There's still room for bigger missions on a Delta IV Heavy, even before the Falcon Heavy flies. We don't do it because there's no point in adding that complexity and the extra expense doesn't give any payback in science. It's better science to send two small probes than one big one.

Falcon Heavy's max payload to Mars is 13,000 kg which is about the size of 1 ISS module. Orion spacecraft is estimated to be 25,000kg with 9,000kg of fuel. Bigger rockets will be necessary, or refueling in space has to be an option.

Comment Re: Why not land on the moon? (Score 1) 303

Your "logic" seems to be that it is impossible to test the new rocket without strapping people on top. This is, of course, nonsense.

Please read above: This was my first post in this thread: "Because you have to walk before you run. Before landing on the moon don't you think NASA should get to the moon first. Apollo 11 was not the first Apollo mission to reach the moon if you remember history."

Two I never said it. My point: Anything new from NASA has to be tested. Even the Apollo era technology was tested. Before Apollo 11 landed on the moon, Apollo 8 and Apollo 10 went to the moon to test various aspects of the mission including orbit and module docking.

Putting a crew on the first attempt to fly a new rocket is foolhardy. To do so on a stack that can fly just fine without a crew is a reckless stunt.

If you read my words, I never advocated for that. But it appears you didn't do so.

Comment Re: Who cares? (Score 1) 303

None at all until you build an industrial city to make use of it. Despite the cheesiness the initial premise of Space 1999 got that right. A huge base several years old with hundreds of people preparing to launch a manned ship to the outer reaches of the solar system.

Here's the problem: At best 95% of every launch's mass goes to escaping gravity. Only 5% is payload. That's for LEO. That's not accounting for travel propulsion beyond Earth. So either building insanely huge rockets with diminishing returns on payload vs mass. Or refuel in orbit. Refueling from Earth means 95% of each launch is to launch 5% fuel. How many launches would it take to fuel a manned Mars mission? The alternative is refueling from the Moon where the escape velocity is 1/5 that of Earth.

It's not going to be an easy plan. But for long term travel within the solar system given the current technology having refueling points beyond Earth make sense.

Comment Re: Why not land on the moon? (Score 1) 303

No, but there is no reason to re-invent the wheel. Apollo did land on the moon, so we have learned from that, so $23 Billion dollars just to fly around it is stupid.

NASA will be not be starting from scratch when it comes to technology learned from Apollo. However the actual equipment itself from Apollo cannot be used. There are no usable Apollo equipment that NASA can use for any moon missions. All the pieces from that era are museum pieces that do not function. NASA will have to re-develop and build everything.

Comment Re: Why not land on the moon? (Score 1) 303

Hardly an illogical position, unless you ignore the existence of unmanned spacecraft.

The logic of the OP: NASA shouldn't use new, "untested" hardware. In other words, NASA should use tech from 50 years. My point: The Apollo tech was also new and untested when NASA first used it. NASA always has to test tech before they use it.

Comment Re: Great idea... But there is a problem... (Score 1) 303

$7k/kg by Falcon Heavy pricing. Would you rather a different launch system?

Have you been paying attention? The proposal is not to launch DIRECTLY from Earth. The word you don't seem to understand is DIRECTLY.

Not really. But the problem is your "lowering prices" standards involves having to send things into to an entirely different gravity well (consumables), and landed propulsively, so that other different things can then be launched from said gravity well.

What? The problem is no one has made a vehicle large enough to launch a manned Mars vehicle. No one. It's not about "lowering" standards. It's about practical limits.

Your proposal, absolutely.

False: It's not my proposal. Experts like at MIT say it's the est option.

From Earth, there are no diminishing returns whatsoever. Just the opposite - the more you launch, the cheaper it gets per kg.

Er? Are you insane? There are always diminishing returns. So the ISS was launched at once will all modules intact or was it built over decades? Why was that? Because no one can build a rocket large enough.

One: completely and utterly false. There are a huge number of different proposals for this, all of them technologically feasible.

List one.

Two: your counterproposal involves doing the same for the moon, and then doing constant resupply so that they can build things that require an entire industrial base there. It's an absurdity.

Again, not my proposal

It does not require a huge infrastructure but it does require infrastructure. The alternative is using Earth to refuel at the high cost of LEO orbit costs.

Incorrect, and an absurd statement to make. The "Journey To Mars" program is the core of NASA's focus. (If it wasn't, nobody would ever put MOXIE on Mars 2020. ;) )

Do we have a manned space vehicle ready for Mars? It is in the planning stages? By YOUR LOGIC, the mission to Mars doesn't exist either.

Comment Re: Who cares? (Score 2) 303

Mars is a pretty terrible candidate for colonization. Both Titan and Venus have better prospects as do asteroid bases.

While I don't think Mars is the best candidate, I would have to disagree that Venus is better. The mean surface temp on Venus is 462C. Also the mandate NASA receives is not to colonize asteroid bases. It is to colonize Mars.

Comment Re: Why not land on the moon? (Score 0) 303

Nonsense. As I stated, the only time NASA launched people on the first flight of a launch system was the Shuttle, and that was only because the Shuttle couldn't be flown and landed remotely.

By the OP's logic, all of NASA's new proposed flights to the moon will be "untested" yet all of Apollo's flight were tested. No, NASA, in each Apollo mission before 11, tested different aspects of the mission. Yet the OP thinks NASA will just strap some astronauts to a moon vehicle this time and hit the launch button. That in landing on the moon with new hardware, NASA won't first test the hardware by launching it at the moon first.

The rest of your response is just fanboy nonsense. NASA has, once again, produced a launch that is too expensive to use. Its safety is unknown and it is foolish to put people on the first flight as a stunt. But, of course, NASA doesn't have the budget to actually test it properly, let alone use it.

Perhaps you would like to read carefully before you levy insults .

Comment Re: Why not land on the moon? (Score 1) 303

No it wasn't. They tested it unmanned. Then they tested it in LEO multiple times. Only then did they send it around the moon. Apollo 8 most likely would have been a failure if not for the earlier testing.

Your logic baffles me: You are saying sending a mission to moon requires "untested" hardware but when NASA did the exact same thing the last time with Apollo 8 and Apollo 10, they were magically tested without having done it before.

Comment Re: Great idea... But there is a problem... (Score 2) 303

Implicit in saying that is the premise that the moon has an industrial base, because you don't make fuel and launch rockets without an industrial base. And an industrial base means dependency chains. And even importing a very small fraction of the amount from Earth to fill gaps in their dependency chains that they launch from the surface would easily price them out of the market. Never mind the absurd capital costs you have to amortize.

What is the cost of launching a Mars vehicle directly from Earth? Insanely high. And it has diminishing returns. There is no practical way to launch a large enough manned vehicle for Mars and have enough fuel to make the trip in a reasonable amount of time (even if it is a one-way trip.). The vast amount of fuel is spent to launch something into orbit; there's little left for the journey. Let's take a look at the Falcon Heavy heavy lift vehicle which is one of the heaviest available right now. The payload to Mars is about 13,000 kg. That is about the weight of 1 ISS module. That module does not include food or supplies; that's just the module weight.

If we go with your plan, NASA will have to launch multiple rockets to build the Mars vehicle and many more rockets to fuel the vehicle. Have you ever thought why no NASA missions to outer space has been refueld? The ISS station gets refueled all the time but not probes. Why is that?

NASA has no plans for a lunar refueling point. It is not part of any actively-being-worked-towards timeline. They've posited the concept before, but they've posited a million fanciful things.

By your logic, NASA has no plans for Mars either.

Slashdot Top Deals

Lead me not into temptation... I can find it myself.

Working...