Hugh Pickens writes:
The cost of getting to orbit is exorbitant, because the rocket, with its multimillion-dollar engines, ends up as trash in the ocean after one launching, something Elon Musk likens to throwing away a [Boeing] 747 jet after a single transcontinental flight. That's why on Tuesday morning at 6:20 a.m. EST his company hopes to upend the economics of space travel in a daring plan by attempting to land the first stage of a Falcon 9 rocket intact on a floating platform, 300 feet long and 170 feet wide in the Atlantic Ocean. SpaceX has attempted similar maneuvers on three earlier Falcon 9 flights, and on the second and third attempts, the rocket slowed to a hover before splashing into the water. “We’ve been able to soft-land the rocket booster in the ocean twice so far,” says Musk. “Unfortunately, it sort of sat there for several seconds, then tipped over and exploded. It’s quite difficult to reuse at that point.”
After the booster falls away and the second stage continues pushing the payload to orbit, its engines will reignite to turn it around and guide it to a spot about 200 miles east of Jacksonville, Florida. Musk puts the chances of success at 50 percent or less but over the dozen or so flights scheduled for this year, “I think it’s quite likely, 80 to 90 percent likely, that one of those flights will be able to land and refly.” SpaceX will offer its own launch webcast on the company's website beginning at 6 a.m. If SpaceX’s gamble succeeds, the company plans to reuse the rocket stage on a later flight. “Reusability is the critical breakthrough needed in rocketry to take things to the next level."
There is plenty of stuff you want to move to orbit that is 100% cheap to replace, but very valuable to get to orbit. Think fuel. So if you land your rocket, and can launch it again, even if it blows up 20% of the time for 2nd launch and 50% of the time for 3rd and consecutive launches, then that already makes fuel more than 50% cheaper to get to LEO.
Financial gain here is the lack of need to build a new 1st (and maybe 2nd) stage; financial loss here is to spend time and money on rebuilding the stages that later explode, and in the loss of payload (it's usually satellites, not fuel,) and in possible damage on the ground. The exact numbers depend on many things, and we cannot say right now what is the right answer. It all depends.
By the way, it would be unwise to hand-wave loss of space fuel. It's usually bad, poisonous stuff like Nitrogen tetroxide, MMH and UDMH. Vaporize ten or twenty tons of stuff near the shore, and it will be pretty bad. It's certainly not something that will advance spaceflight. It may result in lynching of NASA management and canceling the project. Other fuels are not very good for prolonged storage in space.
Secondly, the engines are tested on a test stand for much longer than 300 seconds of power flight. They know that the engines can last many times longer than they need to last.
My numbers are just an example. However continuous firing on a test stand is quite different from a launch and a landing cycle. It remains to be seen if the overhaul of the recovered hardware is worth it. For example, if a car is submerged it becomes an immediate, total write-off.
Reusable rockets is only way we'll get to Mars.
Rockets may bring a human to Mars once, but it is not the way to effectively reach other planets. I would say that a manned trip to Mars is impossible with what we have today. It will simply take too long, and the travel time, combined with harmful environment, will injure astronauts even before they reach Mars. To survive for a year in space astronauts need artificial gravity and protection from energetic particles (space radiation) - it's the bare minimum. But in practice you'd also need life support, ideally a renewable one, and a way to protect people from going insane during the trip.
There are other issues. For example, the pilot will have to operate the lander - without errors, as they would be bad for everyone's health - after a year of never flying it. Furthermore, he cannot fly it even on Earth, as we cannot simulate Martian gravity. He'd have to train on simulators - and he won't have a complete, immersive simulator on the ship. He'd be low on skills and experience by the time they are needed most. This can be fixed by using better engines to reduce travel time. But we don't have those. Until we do, humans will (probably) not set foot on Mars. Add to that the fact that no country on this Earth has money to burn on such a trip.
Spacefuel as in hydrogen/oxygen to get past LEO.
Spacefuel as in hydrogen/oxygen to get past LEO.
Your own link to Wikipedia lists a large number of problems with cryogenic fuels. This is one of reasons why they are not used on long missions - they are very hard to store. A mission to Mars will take about 520 days (if we take Mars-500 as a reference.) You'd have to keep liquid hydrogen in liquid form for all this time, despite heating by the Sun. There is no way to refuel, and there is not enough energy to liquify the gas. Other methods that are listed in the link may or may not be effective. In any case all this infrastructure will cost immense amounts of money, which will not be available because politicians have to deal with stuff on Earth first. And what exactly will the humanity gain from visiting Mars? I'd rather send a thousand robots instead of five bags of salt water. Things will change if robots find an alien spaceship there, for example. But until then there is no point going there in person.
Rockets may bring a human to Mars once, but it is not the way to effectively reach other planets. I would say that a manned trip to Mars is impossible with what we have today. It will simply take too long, and the travel time, combined with harmful environment, will injure astronauts even before they reach Mars.
It's roughly six months each way to Mars. That's not particularly long especially if as you do below, take care of the radiation shielding and introduce some artificial gravity.
To survive for a year in space astronauts need artificial gravity and protection from energetic particles (space radiation) - it's the bare minimum. But in practice you'd also need life support, ideally a renewable one, and a way to protect people from going insane during the trip.
None of which has anything to do with rockets. We could develop all of these and still use current rocket technology to pull the trip off repeatedly.
Things get complicated once you try for something further away than Mars or Venus. A manned trip to Jupiter could be done with chemical rocket engines, but it's going to be a trickier problem due to having at least several years of travel time and the much more considerable delta-v involved. I wouldn't attempt it without at least a better understanding of long term human habitation outside the Van Allen belts.
> To survive for a year in space astronauts need artificial gravity
Nope: http://en.wikipedia.org/wiki/Valeri_Polyakov#Spaceflights [wikipedia.org]
> There are other issues. For example, the pilot will have to operate the lander - without errors, as they would be bad for everyone's health - after a year of never flying it.
Maybe, maybe not. Exactly how to land large, fragile payloads on Mars is still something of an open question, but in the end it may well be something that is better steered by a computer than a person.
> Add to that the fact that no country on this Earth has money to burn on such a trip.We're not talking about countries, we're talking about SpaceX, a rocket company founded by a billionaire whose stated ambition is to retire on Mars, and who has a habit of proving his wild ambitions far more achievable than anybody thought.