Listed below are links to blogs that reference this entry: Missing The Point.
TrackBack URL for this entry: http://www.transterrestrial.com/admin/mt-tb.cgi/10018
12 Comments
ken anthony wrote:
I think it's a case where they're both right. It is over-hyped, but at this stage in the game it has to be over-hyped or it would falter. People doing this have to believe it's part of something bigger or they wouldn't be able to do it at all.
Barnstorming was big for a while, it introduced many people to the concept of passenger flight, but was only a blip on the screen. Long term, suborbital may turn into NY to Tokyo passenger flights, but once people can vacation in orbit, suborbital will not be much of a draw.
Suborbital may lead to high flight rate orbital. That would make it worth while, but it doesn't mean it's not over-hyped for now. Acknowledging everything in the second article doesn't totally invalidate the first.
Orbit is halfway to anywhere. Suborbit is half way to the ground. Still, it is cool and I'm glad there are people willing to take the risk.
8 passengers at $200k is 1.6 million. SpaceX may put 7 passengers into orbit for 6 million. So it's about 4 times the price for 1000 times the experience and both will be available in about the same time frame.
I do agree that we need the engine experience that will be gained even if no passengers are ever flown.
Flight 3 tomorrow??? Wishing them the best.
ken anthony wrote:
OK, not $6 million. I don't know why that number was stuck in my mind.
Brock wrote:
Well, the cost of single Falcon 9 launch to LEO is $36.75M, so divide that by seven (the Dragon capsule's personnel capacity) and you get $5.25M. $6M is probably a good (if low-end) estimate for a one-passenger ticket to LEO.
Still, not bad, compared to what the Soyuz passengers are paying (~$30M ea.).
Gary C Hudson wrote:
With Dragon on an F9, according to SpaceX, the price is more like $80-100M.
This is the most relevant point:
To reach 100 km altitude typically requires a vertical cut-off velocity of 1100 m/s at 40 km altitude. To reach orbit requires a cut-off velocity of 7800 m/s at 185 km altitude—over...7 times the cut-off velocity, and 20 times the energy."
So the SS2 project is 1/20 of an orbital project. If you’re looking for incremental improvements for space access there’s your increment. It seems rather pointless to argue about whether that size step is worthy of hype or not, it is what it is. BTW, costs scale roughly like the power of the machine, so assuming similar flight time scales orbital access should be something like 20 times the cost of an SS2 flight. For an interesting paper on that subject see “Physical Limits to Modularity” By Daniel E Whitney. He explains why access to space will never be cheap, and smashes to bits (pun intended) the comparison of computer cost and rocket costs.
Brian,
Smashing up a straw man can be fun but the debris tends to obscure the argument. Most all successful technologies, not just those based on VLSI, have been developed incrementally. And economies of scale are what drive down prices for products and services regardless of what technology they are based on.
A typical $30k sedan would easily cost ten times more if only a handful of that model were made each year. That price reduction occurs despite the fact that auto technology has "modularity limits". The same holds true for services. A plane ticket would cost a whole lot more if the airline only flew your route of interest once a month rather than once a day. A ticket to space is similarly going to cost less the more the space transport company flies.
Yes, reaching orbit is difficult but that is why incremental development is so crucial. There is, for example, no fundamental physics reason that engines for an orbital vehicle cannot also be robustly enough to withstand hundreds of firings between overhauls. Learning how to build such engines is best done incrementally.
I don't know if your cost scaling with power rule is valid but even if it's true, it means a significant reduction in costs. For example, 20 times $200k means $4M for an orbital ride. That's about a factor of 8 reduction over current Soyuz ticket prices. (Robert Bigelow just jumped for joy!) Rutan and others see suborbital prices falling to the low tens of thousands. I could easily imagine a Lynx seat going for $10K by, say, 2018. So your rule now has people getting people to orbit for $200k per ticket. Sounds like progress to me.
Karl Hallowell wrote:
Given the confusion between what is more important, energy or delta v, and considering that the SpaceShipOne numbers quoted here and in the links are bad. I'll repost my delta v calculation for SpaceShipOne that I did on NASASpaceflight.
Ok, this is off topic, but I'll make an attempt to figure out the various components of delta v here for the SpaceShipOne launch. SpaceShipOne started at about 15 km up and peaked out around 100 km (to barely get into space). In the absence of atmosphere, that's a delta v of roughly 1300 m/s to get that high. Googling around, it appears that the engine fired for 65 seconds straight up. That means that in addition to providing velocity, it had to partially resist gravity for 65 seconds (subtract 640 m/s from the vertical component of velocity). At the top of the peak it had a horizontal velocity of roughly 1200 m/s (mach 3.5).
So in summary 1200 m/s horizontal velocity and roughly 1900 m/s verticle velocity make up the delta v. That's roughly 2250 m/s overall. Some air resistance had to be overcome, but it's probably pretty low (starting at high altitude). Probably less than 50 m/s at a wild guess. Initial velocity was probably much less than 340 m/s (mach 1), but we still get minimum delta v of 1900 m/s from the motor. In comparison, barely attaining a useful orbit is around 9500 m/s plus say 1500 m/s [wrong, 9500 m/s is roughly total delta v including gravity and air resistance losses - Karl] for gravity and air resistance losses. So just launching the motor from the ground would by my calculation at least 17% [corrected to 20% - Karl] of the delta v. Air launch brings that to just over 20% [corrected to almost 25% - Karl] of the necessary delta v to get in a good orbit.
So a total of at least 2250 m/s of delta v was needed by SpaceShipOne to fly that profile. The extra energy needed is rather simple. Energy is cheap. 4 times the delta v is the real problem since it means a much larger mass ratio. That is, you take the mass ratio, fueled launch mass to final "dry" mass, and raise it to the fourth power. Assuming of course, that you continue to use the same hybrid motors that they used for Spaceship One.
Habitat Hermit wrote:
Awesome infoporn post Karl ^_^
brian d wrote:
For example, 20 times $200k means $4M for an orbital ride.
Yup, I agree with that number, 8 people (scaling from SS2) to orbit for about $32M should be achievable. I think a Delta II ride to LEO carries about 12,000lb for about $50M. SS1 weighed about 3000lb, maybe SS2 will check in at around 12,000lb, so sure $32M compares pretty well with real world LVs. I’ve always thought that launches could be done at about ½ the price charged by the bureaucratically challenged big aerospace companies.
john hare wrote:
Once you have reached space altitude as suborbital, much of the unpredictable portions of tthe flight are behind you. Changing aerodynamics from zero velocity at sea level to high subsonic and transonic in fairly dense atmosphere to various supersonic regimes at various densities. Working the gravity losses over the whole velocity and altitude range to minimize losses and so on.
Once your vehicle is over 100 km, the flight regime is predictable. No drag, and gravity losses are compensated by mild pitch variations applied gradually. It is more like getting 4,000 miles range out of a 200 mile range car than taking your 100 mph car to 500 mph. Both require work, just not as much for the first case.
Karl Hallowell wrote:
I might add that Jon Goff inspired that calculation. I can't locate the particular article, but he criticized the way people were belittling SpaceShipOne based on faulty energy comparisons or greatly underestimating the delta v.
Leave a comment
Note: The comment system is functional, but timing out when returning a response page. If you have submitted a comment, DON'T RESUBMIT IT IF/WHEN IT HANGS UP AND GIVES YOU A "500" PAGE. Simply click your browser "Back" button to the post page, and then refresh to see your comment.
About this Entry
This page contains a single entry by Rand Simberg published on July 31, 2008 6:29 AM.
I think it's a case where they're both right. It is over-hyped, but at this stage in the game it has to be over-hyped or it would falter. People doing this have to believe it's part of something bigger or they wouldn't be able to do it at all.
Barnstorming was big for a while, it introduced many people to the concept of passenger flight, but was only a blip on the screen. Long term, suborbital may turn into NY to Tokyo passenger flights, but once people can vacation in orbit, suborbital will not be much of a draw.
Suborbital may lead to high flight rate orbital. That would make it worth while, but it doesn't mean it's not over-hyped for now. Acknowledging everything in the second article doesn't totally invalidate the first.
Orbit is halfway to anywhere. Suborbit is half way to the ground. Still, it is cool and I'm glad there are people willing to take the risk.
8 passengers at $200k is 1.6 million. SpaceX may put 7 passengers into orbit for 6 million. So it's about 4 times the price for 1000 times the experience and both will be available in about the same time frame.
I do agree that we need the engine experience that will be gained even if no passengers are ever flown.
Flight 3 tomorrow??? Wishing them the best.
OK, not $6 million. I don't know why that number was stuck in my mind.
Well, the cost of single Falcon 9 launch to LEO is $36.75M, so divide that by seven (the Dragon capsule's personnel capacity) and you get $5.25M. $6M is probably a good (if low-end) estimate for a one-passenger ticket to LEO.
Still, not bad, compared to what the Soyuz passengers are paying (~$30M ea.).
With Dragon on an F9, according to SpaceX, the price is more like $80-100M.
http://www.aviationweek.com/aw/generic/story.jsp?id=news/SPACEX05148.xml&headline=SpaceX%20Claims%20Crew%20Transfer%20Ability%20By%202011&channel=space
...says about 7.5
This is the most relevant point:
To reach 100 km altitude typically requires a vertical cut-off velocity of 1100 m/s at 40 km altitude. To reach orbit requires a cut-off velocity of 7800 m/s at 185 km altitude—over...7 times the cut-off velocity, and 20 times the energy."
So the SS2 project is 1/20 of an orbital project. If you’re looking for incremental improvements for space access there’s your increment. It seems rather pointless to argue about whether that size step is worthy of hype or not, it is what it is. BTW, costs scale roughly like the power of the machine, so assuming similar flight time scales orbital access should be something like 20 times the cost of an SS2 flight. For an interesting paper on that subject see “Physical Limits to Modularity” By Daniel E Whitney. He explains why access to space will never be cheap, and smashes to bits (pun intended) the comparison of computer cost and rocket costs.
Brian,
Smashing up a straw man can be fun but the debris tends to obscure the argument. Most all successful technologies, not just those based on VLSI, have been developed incrementally. And economies of scale are what drive down prices for products and services regardless of what technology they are based on.
A typical $30k sedan would easily cost ten times more if only a handful of that model were made each year. That price reduction occurs despite the fact that auto technology has "modularity limits". The same holds true for services. A plane ticket would cost a whole lot more if the airline only flew your route of interest once a month rather than once a day. A ticket to space is similarly going to cost less the more the space transport company flies.
Yes, reaching orbit is difficult but that is why incremental development is so crucial. There is, for example, no fundamental physics reason that engines for an orbital vehicle cannot also be robustly enough to withstand hundreds of firings between overhauls. Learning how to build such engines is best done incrementally.
I don't know if your cost scaling with power rule is valid but even if it's true, it means a significant reduction in costs. For example, 20 times $200k means $4M for an orbital ride. That's about a factor of 8 reduction over current Soyuz ticket prices. (Robert Bigelow just jumped for joy!) Rutan and others see suborbital prices falling to the low tens of thousands. I could easily imagine a Lynx seat going for $10K by, say, 2018. So your rule now has people getting people to orbit for $200k per ticket. Sounds like progress to me.
Given the confusion between what is more important, energy or delta v, and considering that the SpaceShipOne numbers quoted here and in the links are bad. I'll repost my delta v calculation for SpaceShipOne that I did on NASASpaceflight.
Ok, this is off topic, but I'll make an attempt to figure out the various components of delta v here for the SpaceShipOne launch. SpaceShipOne started at about 15 km up and peaked out around 100 km (to barely get into space). In the absence of atmosphere, that's a delta v of roughly 1300 m/s to get that high. Googling around, it appears that the engine fired for 65 seconds straight up. That means that in addition to providing velocity, it had to partially resist gravity for 65 seconds (subtract 640 m/s from the vertical component of velocity). At the top of the peak it had a horizontal velocity of roughly 1200 m/s (mach 3.5).
So in summary 1200 m/s horizontal velocity and roughly 1900 m/s verticle velocity make up the delta v. That's roughly 2250 m/s overall. Some air resistance had to be overcome, but it's probably pretty low (starting at high altitude). Probably less than 50 m/s at a wild guess. Initial velocity was probably much less than 340 m/s (mach 1), but we still get minimum delta v of 1900 m/s from the motor. In comparison, barely attaining a useful orbit is around 9500 m/s plus say 1500 m/s [wrong, 9500 m/s is roughly total delta v including gravity and air resistance losses - Karl] for gravity and air resistance losses. So just launching the motor from the ground would by my calculation at least 17% [corrected to 20% - Karl] of the delta v. Air launch brings that to just over 20% [corrected to almost 25% - Karl] of the necessary delta v to get in a good orbit.
So a total of at least 2250 m/s of delta v was needed by SpaceShipOne to fly that profile. The extra energy needed is rather simple. Energy is cheap. 4 times the delta v is the real problem since it means a much larger mass ratio. That is, you take the mass ratio, fueled launch mass to final "dry" mass, and raise it to the fourth power. Assuming of course, that you continue to use the same hybrid motors that they used for Spaceship One.
Awesome infoporn post Karl ^_^
For example, 20 times $200k means $4M for an orbital ride.
Yup, I agree with that number, 8 people (scaling from SS2) to orbit for about $32M should be achievable. I think a Delta II ride to LEO carries about 12,000lb for about $50M. SS1 weighed about 3000lb, maybe SS2 will check in at around 12,000lb, so sure $32M compares pretty well with real world LVs. I’ve always thought that launches could be done at about ½ the price charged by the bureaucratically challenged big aerospace companies.
Once you have reached space altitude as suborbital, much of the unpredictable portions of tthe flight are behind you. Changing aerodynamics from zero velocity at sea level to high subsonic and transonic in fairly dense atmosphere to various supersonic regimes at various densities. Working the gravity losses over the whole velocity and altitude range to minimize losses and so on.
Once your vehicle is over 100 km, the flight regime is predictable. No drag, and gravity losses are compensated by mild pitch variations applied gradually. It is more like getting 4,000 miles range out of a 200 mile range car than taking your 100 mph car to 500 mph. Both require work, just not as much for the first case.
I might add that Jon Goff inspired that calculation. I can't locate the particular article, but he criticized the way people were belittling SpaceShipOne based on faulty energy comparisons or greatly underestimating the delta v.