First Privately-Funded Manned Mission to Space

[Mark]

Yes. I think they have the best chances of winning. It will still be some time before a space flight becomes affordable, though; I recall reading on their website that the price for a few minutes in space would be comparable to a round-the-world trip.

From top to bottom, what has so far been achieved by them cost in the vicinity of $20 million, from what I understand (and they still have the vehicle, design, etc.) Costs should be dropping immediately for their next effort, I'd imagine. One of the requirements, though, for the big prize is a flight with three people, I believe.

 

[Umbran]

Costs should be dropping immediately for their next effort, I'd imagine. One of the requirements, though, for the big prize is a flight with three people, I believe.

With three people, or one pilot, and equivalent weight in a ship design that really could have the people in it. And then doing a second flight within two weeks. There are some other limitations - can't replace more than 10% of the ship's non-fuel mass between flights, for example.

The thing is, Rutan and Scaled Composites have stated that they themselves are not interested in doing tourist flights. Maybe they'll sell or license the design, but they won't be doing it themselves. Rutan has said that if this works, he's next going to set his sights on reaching orbit.

No mean feat, considering that the current ship only does about Mach 3. That's nowhere near the speed you need for orbit.

 

[Mark]

No mean feat, considering that the current ship only does about Mach 3. That's nowhere near the speed you need for orbit.

Doesn't that depend on the payload? Even so, are jet sled ramps or expendable boosters not acceptable if they can be made to not exceed the 10% replacement allowance?

 

[Umbran]

Doesn't that depend on the payload?

Nope. In order to keep a particular orbit, you need to reach a certain speed. Whether or not a particular rocket will get you to that speed is payload dependant. But a heavy payload or a light payload both have to move at the same clip.

Even so, are jet sled ramps or expendable boosters not acceptable if they can be made to not exceed the 10% replacement allowance?

Expendable boosters would be, but I severely doubt you'd keep them under the 10% limit. A recoverable booster would be better. That, in a sense, is what the White Knight is, after all. I don't know about jet sled ramps. There aren't all that many mountains placed well for reaching orbit anyway.

All of which is kind of moot. The Ansari X-Prize is about reaching a sub-orbital 100 km up. There's currently no competition for reaching orbit, so there's no need to meet the 10% rule or anything for that goal. Yet...

 

[Mark]

Nope. In order to keep a particular orbit, you need to reach a certain speed. Whether or not a particular rocket will get you to that speed is payload dependant. But a heavy payload or a light payload both have to move at the same clip.

Doesn't the speed requirement lessen as the height of the orbit becomes higher?

Expendable boosters would be, but I severely doubt you'd keep them under the 10% limit. A recoverable booster would be better. That, in a sense, is what the White Knight is, after all. I don't know about jet sled ramps. There aren't all that many mountains placed well for reaching orbit anyway.

All of which is kind of moot. The Ansari X-Prize is about reaching a sub-orbital 100 km up. There's currently no competition for reaching orbit, so there's no need to meet the 10% rule or anything for that goal. Yet...

I see. Thanks!

 

[Umbran]

Doesn't the speed requirement lessen as the height of the orbit becomes higher?

No.

As the height (actually radius) of the orbit gets larger, the kinetic energy of the orbiting object drops, yes. But that's not the whole story.

I'll try to do this without equations...

In order to get a thing into orbit, you need to do two things. You need to lift it high off the ground, and you have to give it some orbital speed so it doesn't fall back. Your rocket burn must provide both of these - give the payload enough kinetic energy to coast up, and also stay in orbit. That means that the higher you want the thing to go, the faster it needs to be going when the rocket shuts off.

 

[Mark]

No.

As the height (actually radius) of the orbit gets larger, the kinetic energy of the orbiting object drops, yes. But that's not the whole story.

I'll try to do this without equations...

In order to get a thing into orbit, you need to do two things. You need to lift it high off the ground, and you have to give it some orbital speed so it doesn't fall back. Your rocket burn must provide both of these - give the payload enough kinetic energy to coast up, and also stay in orbit. That means that the higher you want the thing to go, the faster it needs to be going when the rocket shuts off.

Interesting. Thanks. I would have thought that once you were up there in a very high orbit you could fire some other supplementary boosters to bring it up to a speed that would allow you to then maintain an orbit, and at a high enough orbit not require a great deal of speed. I would have thought that once you get to the point where the mass and gravity of a body that was being orbited was low enough, a very minimal speed could be maintained, virtually riding a cusp where any slower and you drop but any faster and you might break orbit.

 

[Umbran]

Interesting. Thanks. I would have thought that once you were up there in a very high orbit you could fire some other supplementary boosters to bring it up to a speed that would allow you to then maintain an orbit, and at a high enough orbit not require a great deal of speed.

Remember, there's two parts - getting up to altitude, and getting speed to stay in orbit. Yes, once you are high up, you don't need to be moving fast. But you need to be moving fast to get up to altitude.

Take a baseball. Toss it up lightly. It isn't moving very fast when it leaves your hand, so it doesn't go very high up. Take it, and throw it upwards with all your might. It is going much faster, so it goes higher.

I would have thought that once you get to the point where the mass and gravity of a body that was being orbited was low enough, a very minimal speed could be maintained, virtually riding a cusp where any slower and you drop but any faster and you might break orbit.

Well, first of all, you're confusing mass and weight. The mass of the body does not decrease as you get farther from the Earth, and it is the mass you care about here.

Next - there isn't a simple single cusp. There's a broad range of possible orbits. If you break escape velocity, you leave orbit completely. But short of that, there's a whole continuum of orbits. Each characterized by a different total energy of the orbiting body. If you don't meet a particular orbit, you don't necessarily fall out of the sky. You may just take another orbit. You only fall out of the sky when your energy is such that your orbit intersects the atmosphere.

 

[Mark]

Remember, there's two parts - getting up to altitude, and getting speed to stay in orbit. Yes, once you are high up, you don't need to be moving fast. But you need to be moving fast to get up to altitude.

Take a baseball. Toss it up lightly. It isn't moving very fast when it leaves your hand, so it doesn't go very high up. Take it, and throw it upwards with all your might. It is going much faster, so it goes higher.

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Well, first of all, you're confusing mass and weight. The mass of the body does not decrease as you get farther from the Earth, and it is the mass you care about here.

Next - there isn't a simple single cusp. There's a broad range of possible orbits. If you break escape velocity, you leave orbit completely. But short of that, there's a whole continuum of orbits. Each characterized by a different total energy of the orbiting body. If you don't meet a particular orbit, you don't necessarily fall out of the sky. You may just take another orbit. You only fall out of the sky when your energy is such that your orbit intersects the atmosphere.

Thanks for the additional detail, and my bad for not reworking the sentence further than I did regarding mass. I started out with a bit about the influence of a mass, switched to gravity of a body, and never properly cleaned it up. I never meant to bring weight into that part of the discussion.

Feel like describing escape velocity, payload potential, and detailing likely volumes of fuel needed by some of the entries, and how those things effect their chances of success (for the contest and for future viability as public vehicles)? I'm keen to hear your views.

 

[Umbran]

Feel like describing escape velocity, payload potential, and detailing likely volumes of fuel needed by some of the entries, and how those things effect their chances of success (for the contest and for future viability as public vehicles)? I'm keen to hear your views.

Well, the detailed specs of the entries are not generally open to the public, so I'm not really in a position to speculate much on what the machines can do, and how cheaply they can do it.

For the contest - I'll be very, very surprised if anyone coems close to challenging Rutan and Scaled Composites for the prize. Rutan is perhaps the best aeronautics/aerospace engineer in the world. And he's repeatedly shown that he has a level head, good design, and knows how to run a testing program without busting a budget.

As for future success of these vehicles for the public - well, all the X-prize entries are really good for is tourism. They are not built to lift heavy payloads, nor do they go anywhere that's commercially useful. So, convenience, safety, and fun for the tourist are paramount.

To that end - any system that uses a parachute splashdown is a poor candidate for public use. If the tourist is spending thousands of dollars on a thrill ride, they don't then want to have to spend hours getting plucked out of the water and brought back to land. That's just boring. Those systems like Space Ship One that land on a runway are far better for tourist application. You can set up such a system near most airports that have good weather, which is great for a tourism application.

My personal opinion is that the hybrid engine design of Space Ship One is very good for such applications. It doesn't have nearly the punch of a more standard liquid hydrogen/oxygen rocket, but it doesn't need big punch to reach 100 km up with only a few bodies as payload, and the fuel is a darned sight safer to be around, and more easy to use than more conventional rocket fuels.

That being said - any team trying a really radical approach is apt to meet defeat, both in the competition and in the private sector. Really radical approaches are simply too unreliable and risky for investors and tourists.