Commerical Suborbital Point-to-Point

[go4mars]

Yeah right.  That is Thunderbirds and not reality.   You are just showing that it is more limited than Concorde by coming up with ridiculous schemes. 

What's a realistic diameter for a sonic-boom trouble area where a capsule on a ballistic trajectory re-enters.  I'm guessing 4 miles radius at 60k feet growing to 8 miles radius when it gets subsonic at 12 or 15 thousand feet?   Traced out centered on a linear locus on the land.                  Does that seem about right?

[Jim]

Yeah right.  That is Thunderbirds and not reality.   You are just showing that it is more limited than Concorde by coming up with ridiculous schemes. 

What's a realistic diameter for a sonic-boom trouble area where a capsule on a ballistic trajectory re-enters.  I'm guessing 4 miles radius at 60k feet growing to 8 miles radius when it gets subsonic at 12 or 15 thousand feet?   Traced out centered on a linear locus on the land.                  Does that seem about right?

No, .5 psf as far away as 30 miles

[douglas100]

And it's not just the sonic boom. What about the noise of launching?

[go4mars]

And it's not just the sonic boom. What about the noise of launching?

What about it?  Inconsequential compared to 30 miles.

[douglas100]

Inconsequential? Not to the people living close to large airports. They have to tolerate enough noise already.

Concorde had a struggle to get into JFK because of the noise it made. There's no way a rocket powered vehicle would be allowed to operate from a suburban airport because of noise. If you argue that suborbital vehicles are going to be flown from spaceports away from population centres, then the "flexibility" you touted earlier disappears. And you would have a very large investment in new infrastructure. And there are countries which are just too densely populated to site such spaceports.

The only way you could operate from existing airports would be if the vehicle fitted the existing traffic patterns and noise limits. That means a winged horizontal take off, air breathing engines which are not too loud and a transition to rocket propulsion at altitude. It requires an advanced heat shield. In short, something like Skylon.

And also, it will not have a safety level comparable to present air travel. Current launch vehicles are nowhere near this level. It will take thousands of flights to achieve this.

All this for a market that is not at all assured.

[chrisking0997]

do not underestimate the power of the NIMBY

[Robotbeat]

I believe there very much would be a market for this. Provided it's cheap enough, SAFE ENOUGH, and as long as the NIMBY issues can addressed. Also, you'd have to streamline the boarding issues to make it worth it. But there are people who are so much richer than you and I can really grasp. CEO average compensation is ~$12.8 million a year. Some are compensated in the range of $200 million per year, which could well be enough to charter their own personal supersonic/suborbital aircraft (with dedicate pilot(s)).

Safety is really the most important issue. And it can be addressed with a high enough flight rate.

One of the most important points of this discussion, though, is that there is no way commercial suborbital point-to-point will be an early market for companies like XCOR. It will only happen after significant performance increases and a lot more mature systems, if it happens at all.

[go4mars]

Inconsequential? ...

You think the noise would be a problem from 30 miles away from launch? 

[go4mars]

...companies like XCOR. It will only happen after significant performance increases and a lot more mature systems,

But all this discussion about the limitations of it from a noise perspective really do lend more potential to a horizontal takeoff type of system.  Like a stratolauncher with a passenger section instead of a second stage. 

[Robotbeat]

...companies like XCOR. It will only happen after significant performance increases and a lot more mature systems,

But all this discussion about the limitations of it from a noise perspective really do lend more potential to a horizontal takeoff type of system.  Like a stratolauncher with a passenger section instead of a second stage. 

Increased operational costs and a lot longer time from passenger boarding to launch (since you have to wait for the Stratolauncher to slowly climb to altitude), defeating much of the point. This is why I suspect XCOR's vehicle will be significantly more cost-effective than Virgin Galactic's, in spite of the fact that XCOR's vehicle will have a lot less seating.

[go4mars]

...a lot longer time from passenger boarding to launch (since you have to wait for the Stratolauncher to slowly climb to altitude), defeating much of the point. This is why I suspect XCOR's vehicle will be significantly more cost-effective than Virgin Galactic's, in spite of the fact that XCOR's vehicle will have a lot less seating.

Good points, but isn't it possible that the rocket could be dropped and lit at a lot lower altitude?  Maybe just get up a few thousand feet about ground level and far enough from big cranky population bases.  That could be just ten minutes or so.  30k+ feet might not be mandatory.

[douglas100]

Inconsequential? ...

You think the noise would be a problem from 30 miles away from launch? 

That's not what I said. I said it would be a problem for people living near suburban airports, the people you dismissed as "big cranky population bases."

[douglas100]

I believe there very much would be a market for this. Provided it's cheap enough, SAFE ENOUGH, and as long as the NIMBY issues can addressed. Also, you'd have to streamline the boarding issues to make it worth it. But there are people who are so much richer than you and I can really grasp. CEO average compensation is ~$12.8 million a year. Some are compensated in the range of $200 million per year, which could well be enough to charter their own personal supersonic/suborbital aircraft (with dedicate pilot(s)).

I agree with all that, but I still doubt that there's much of a market presently. If there is a demand from the super rich that you cite, why is p2p not already in development?

[go4mars]

I didn't mean to brush you off by being flippant.  I put in bold the place where I think our communication broke down. 

No, .5 psf as far away as 30 miles

And it's not just the sonic boom. What about the noise of launching?

...Inconsequential compared to 30 miles.

Inconsequential? ...

You think the noise would be a problem from 30 miles away from launch?

That's not what I said.

[A_M_Swallow]

I believe there very much would be a market for this. Provided it's cheap enough, SAFE ENOUGH, and as long as the NIMBY issues can addressed. Also, you'd have to streamline the boarding issues to make it worth it. But there are people who are so much richer than you and I can really grasp. CEO average compensation is ~$12.8 million a year. Some are compensated in the range of $200 million per year, which could well be enough to charter their own personal supersonic/suborbital aircraft (with dedicate pilot(s)).

I agree with all that, but I still doubt that there's much of a market presently. If there is a demand from the super rich that you cite, why is p2p not already in development?

I suspect too expensive for a small firm and the large firms wanted a government contract.  There was never a personal supersonic jet.  Supersonic jet engines were sized for fighters or Concorde.

[RanulfC]

Couple of quick semi-technical notes

1) Any "sonic-boom" above 100,000ft never touches the ground, ie is not an issue.

2) At one point it was figured for the suggested V-Prize, (P2P America-to-Europe) that an average speed of around Mach-6 was the minimum requirement to meet the time suggested.

3) A "Skip-Glide" trajectory can get you the same range as a ballistic trajectory with less "initial" Delta-V required as you can use external burning along the fuselage using internal fuel but external oxidizer (air) to extend each "skip" step which requires less overall propellant than pileing on all the delta-V at that start of the flight.

4) While the interval between "skips" means that individual zero-gee portions are shorter the overall total zero-gee time is about the same if not longer than for a pure ballistic trajectory.

5) There are questions of passenger comfort for the multiple positive-g/negative-g portions of the flight.

Randy

[Robotbeat]

I believe there very much would be a market for this. Provided it's cheap enough, SAFE ENOUGH, and as long as the NIMBY issues can addressed. Also, you'd have to streamline the boarding issues to make it worth it. But there are people who are so much richer than you and I can really grasp. CEO average compensation is ~$12.8 million a year. Some are compensated in the range of $200 million per year, which could well be enough to charter their own personal supersonic/suborbital aircraft (with dedicate pilot(s)).

I agree with all that, but I still doubt that there's much of a market presently. If there is a demand from the super rich that you cite, why is p2p not already in development?

It is in development. Virgin Galactic has said it's working on it or sees it as one of the potential markets for their series of suborbital spacecraft/aircraft.

Now, the level of intensity of that development is another question. And I'm skeptical that it will be successful anytime soon. I suspect it will be a while. But there is demand for a safe, fast transport if someone can do it cheap enough (I'd guess it'll take at least a couple decades).

[douglas100]

Now, the level of intensity of that development is another question. And I'm skeptical that it will be successful anytime soon. I suspect it will be a while. But there is demand for a safe, fast transport if someone can do it cheap enough (I'd guess it'll take at least a couple decades).

I agree about the timescale.

[mrmandias]

To make a profit the price of the tickets will have to be a high, will even millionaires pay the price?

The majority of Concord's passengers were either very wealthy or had their passage paid for by their employers on business trips that the corporations deemed worth the expense. For business trips, the cost of transportation is a tax write-off so I believe that those corporations that sent their executives on Concord flights would not hesitate to book them on P2P. It doesn't come out of their pockets - they would simply write it off on their taxes. Instant market.

A write-off doesn't mean its free, it means the cost is reduced by the business' marginal tax rate.

[HMXHMX]

Couple of quick semi-technical notes

1) Any "sonic-boom" above 100,000ft never touches the ground, ie is not an issue.

2) At one point it was figured for the suggested V-Prize, (P2P America-to-Europe) that an average speed of around Mach-6 was the minimum requirement to meet the time suggested.

3) A "Skip-Glide" trajectory can get you the same range as a ballistic trajectory with less "initial" Delta-V required as you can use external burning along the fuselage using internal fuel but external oxidizer (air) to extend each "skip" step which requires less overall propellant than pileing on all the delta-V at that start of the flight.

4) While the interval between "skips" means that individual zero-gee portions are shorter the overall total zero-gee time is about the same if not longer than for a pure ballistic trajectory.

5) There are questions of passenger comfort for the multiple positive-g/negative-g portions of the flight.

Randy

Regarding (1) I've heard the Shuttle Orbiter double boom over the SF Peninsula, and I think it was at 200K ft. 

Regarding (5), Arthur Clarke had an amusing line about sub-orbital P2P: "Half the time the toilet is out of order and the other half the time it is out of reach."