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Cost of launch and laws of physics



 
 
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  #1  
Old August 5th 03, 07:20 PM
Greg Kuperberg
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Default Cost of launch and laws of physics

A couple of months ago Wired Magazine quoted John Pike as saying,
"It costs $10,000 a pound to get into space, and the reason isn't the
government - it's physics." A lot of people here devoted many postings
to ridiculing this comment. Some were not content to refute the statement
and also questioned Pike's credentials, political ideology, and intellect.

The comment was an off-the-cuff exaggeration, but one interpretation
of it is true enough. Of course there is no physics equation that
produces $10,000 per pound or any other value for the cost of launch.
What is true is that the organization that actually launch things into
space (NASA, Boeing, the Russians, etc.) don't just spend tons of money
on bureaucracy. Rather, they also spend tons of money coping with laws
of physics. It's not like Coca-Cola, which could be 20 times cheaper if
it were just the syrup and no marketing. Launching a rocket into orbit
takes talented engineers, special materials, and painstaking inspections,
because usefully travelling at 12,000 miles an hour is really hard.

Think how much harder it is to build a car that goes 120 mph than a
bicycle that goes 12 mph. Now think how much harder it is build a jet
that goes 1,200 mph than a car. Now take it one step further and you've
got the difficulty of manned spaceflight. Of course doing any of these
in expendable, unmanned form is much easier, which is part of the reason
that most space rockets are expendable and unmanned.

The flip side of this is that many of the CATS/RLV/X-Prize believers
don't seem to take the laws of physics very seriously. For example,
another Wired article quotes Gary Hudson as follows: "That leaves the most
frequently asked question about the Roton: wouldn't the rotor blades burn
off in the atmosphere? The remarkable - and counterintuitive - answer
is No." Given what happened to the space shuttle Columbia,
that is a fair question. Just calling the answer counterintuitive and
remarkable doesn't make it right.

Okay, I imagine that someone will tell me that I'm quoting out of context.
So here is the context:

That leaves the most frequently asked question about the Roton:
wouldn't the rotor blades burn off in the atmosphere? The remarkable -
and counterintuitive - answer is No. During the long climb into orbit,
the atmosphere steadily decreases in density. The Roton starts out at
very low speeds in the high-density atmosphere. As it picks up speed
and climbs higher, the atmosphere thins out. The "dynamic pressure"
(think wind) would actually be lower for the Roton than for many
high-performance aircraft, including fighters.

During reentry, the Roton would encounter a pretty benign environment
as well. The Roton would start out at high speeds, but the atmosphere
would be very thin. As the atmosphere becomes more dense at lower
altitudes, the rotor would slow the vehicle down. Also, the load on
the blades would be rather small because most of the propellant would
have been consumed - meaning more than 90 percent of the overall
weight would be gone. Wind tunnel tests have shown the heating
would be no worse than that experienced by the space shuttle or
other reentry vehicles.

The heating would be "no worse" than that experienced by the space
shuttle? Hmm...
--
/\ Greg Kuperberg (UC Davis)
/ \
\ / Visit the Math ArXiv Front at http://front.math.ucdavis.edu/
\/ * All the math that's fit to e-print *
  #2  
Old August 5th 03, 08:33 PM
Greg Kuperberg
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Default Cost of launch and laws of physics

In article ,
Rand Simberg wrote:
Think how much harder it is to build a car that goes 120 mph than a
bicycle that goes 12 mph. Now think how much harder it is build a jet
that goes 1,200 mph than a car. Now take it one step further and you've
got the difficulty of manned spaceflight.


Funny thing is, it doesn't cost much more to to fly across country
than it does to drive, especially when one takes the full costs
(depreciation, etc.) into account.


But that's not the cost per pound, that's the cost per pound *per mile*.
Assuming 120 orbits, the space shuttle travels 3 million miles, which
at $10,000 per pound is 1/3 of a cent per pound per mile. That's only
3 to 10 times as high as a plane ticket, not two orders of magnitude.

Heck, an LEO satellite might have 50,000 useful orbits, while Saturn is a
billion miles away. Space is already the cheapest form of transportation
counting your way. :-)

--
/\ Greg Kuperberg (UC Davis)
/ \
\ / Visit the Math ArXiv Front at http://front.math.ucdavis.edu/
\/ * All the math that's fit to e-print *
  #4  
Old August 5th 03, 09:19 PM
Greg Kuperberg
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Posts: n/a
Default Cost of launch and laws of physics

In article ,
Rand Simberg wrote:
Think how much harder it is to build a car that goes 120 mph than a
bicycle that goes 12 mph. Now think how much harder it is build a jet
that goes 1,200 mph than a car. Now take it one step further and you've
got the difficulty of manned spaceflight.

....
Funny thing is, it doesn't cost much more to to fly across country
than it does to drive, especially when one takes the full costs
(depreciation, etc.) into account.

....
But that's not the cost per pound, that's the cost per pound *per mile*.

....
Ummmm...no. I said nothing about cost per mile--I said cost per
transcontinental trip.


Well that's cheating in a different way. First, you changed 1200 mph
to 500. 1200 mph is a Concorde, not a jumbo jet. A transcontinental
Concorde trip is a full order of magnitude more expensive than by car
at 120 mph. (Okay, not counting speeding tickets.)

Second, you are comparing a Concorde to a space rocket on the Concorde's
distance scale, 3,000 miles, rather than on the rocket's distance scale,
which is 300,000 miles (at least!). So let's compare the Concorde to
a car on the car's distance scale, 30 miles. One would be 5 dollars
per passenger, the other would be $500 (maybe). So that's two orders
of magnitude right there.

For that matter, a transcontinental ballistic trajectory is suborbital
and therefore much cheaper than $3,000 per pound (as quoted by Lambeth
for orbital flight).

Granted, some forms of travel have special discounts during silly season.
--
/\ Greg Kuperberg (UC Davis)
/ \
\ / Visit the Math ArXiv Front at http://front.math.ucdavis.edu/
\/ * All the math that's fit to e-print *
  #5  
Old August 5th 03, 09:39 PM
Rand Simberg
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Default Cost of launch and laws of physics

On Tue, 5 Aug 2003 20:19:18 +0000 (UTC), in a place far, far away,
(Greg Kuperberg) made the phosphor on
my monitor glow in such a way as to indicate that:

Ummmm...no. I said nothing about cost per mile--I said cost per
transcontinental trip.


Well that's cheating in a different way. First, you changed 1200 mph
to 500. 1200 mph is a Concorde, not a jumbo jet. A transcontinental
Concorde trip is a full order of magnitude more expensive than by car
at 120 mph.


Sorry, I didn't pay close attention to the speed you wrote. I thought
you were talking about conventional air transports.

Concorde is more expensive for two reasons--it has much higher drag
(mostly due, directly or indirectly, to shock) resulting in several
times the unit fuel consumption (its L/D ratio is less than half that
of a modern subsonic transport), and it's not flown very much, so it's
difficult to amortize the fixed costs (the same problem we have with
launch costs).

And in fact, I would argue that physics is a much stronger factor in
keeping the costs of supersonic flight high than it is in keeping
launch costs high. There are things we can do to dramatically reduce
launch costs with known physics, but there's little we can do to
reduce supersonic flight costs without a better understanding of
supersonic aerodynamics and vehicle design.

Second, you are comparing a Concorde to a space rocket on the Concorde's
distance scale, 3,000 miles, rather than on the rocket's distance scale,
which is 300,000 miles (at least!).


As you pointed out yourself (or at least it seemed, cost per distance
is an absurd measure to compare space transport with ground or air
transport. I don't know why you do it.

So let's compare the Concorde to
a car on the car's distance scale, 30 miles. One would be 5 dollars
per passenger, the other would be $500 (maybe). So that's two orders
of magnitude right there.


Yes, because it would be idiotic (and not possible, in a business
sense) to fly a Concorde thirty miles. My point was that under
realistic circumstances (which short haul on a Concorde is not, though
many people drive, or take trains, across the country) the costs of
cars and aircraft aren't that different, so the comparison on which
you're basing your comparison between air and space is invalid.

You're really flaunting your own ignorance of the source of high
launch costs, here, Greg.

--
simberg.interglobal.org * 310 372-7963 (CA) 307 739-1296 (Jackson Hole)
interglobal space lines * 307 733-1715 (Fax)
http://www.interglobal.org

"Extraordinary launch vehicles require extraordinary markets..."
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  #6  
Old August 5th 03, 10:07 PM
jeff findley
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Default Cost of launch and laws of physics

(Greg Kuperberg) writes:

A couple of months ago Wired Magazine quoted John Pike as saying,
"It costs $10,000 a pound to get into space, and the reason isn't the
government - it's physics." A lot of people here devoted many postings
to ridiculing this comment. Some were not content to refute the statement
and also questioned Pike's credentials, political ideology, and intellect.


John Pike has no qualifications to make this claim. Note that even on
his own, self promoting, web page, he makes no mention of any degrees
or any real experience that would qualify him to make such a claim.

http://www.globalsecurity.org/org/staff/pike.htm

Others on John Pike's staff
(http://www.globalsecurity.org/org/staff/index.html) hold degrees in:

1. Masters Degree (D.E.A.) in Political Studies
2. Bachelors Degree in International Studies (Masters Candidate Security
Policy Studies )
3. Bachelor of Arts degree
4. degree in International Service
5. Ph.D. in chemistry from Lehigh University in 1984 for the study of
tissue lytic proteins produced by the human pathogen Vibrio
vulnificus, a microorganism responsible for a type of "flesh-eating"
disease in those with compromised immune systems
6. Associate of Applied Science degree in Mechanical Engineering
Technology
7. Masters Degree in History

None of these people has a background that would qualify them to make
the statement that Pike made.

The comment was an off-the-cuff exaggeration, but one interpretation
of it is true enough.


I don't think so. There was nothing in the statement that indicated
that he was exaggerating.

The flip side of this is that many of the CATS/RLV/X-Prize believers
don't seem to take the laws of physics very seriously. For example,
another Wired article quotes Gary Hudson as follows: "That leaves the most
frequently asked question about the Roton: wouldn't the rotor blades burn
off in the atmosphere? The remarkable - and counterintuitive - answer
is No." Given what happened to the space shuttle Columbia,
that is a fair question. Just calling the answer counterintuitive and
remarkable doesn't make it right.


Anyone with any qualifications would know that what Gary said is true.
Roton would have been mostly empty tankage. As such, the heating it
experiences on re-entry would be much less than the much more dense
shuttle (which drops its large, empty tank before reaching orbit).
Roton would do much of its decelleration very high in the atmosphere
where the dynamic pressure is low. The shuttle, being very dense,
simply can't. It's apples and oranges to anyone who understands a bit
of the physics (something that Pike clearly does not understand).

Jeff
--
Remove "no" and "spam" from email address to reply.
If it says "This is not spam!", it's surely a lie.
  #8  
Old August 5th 03, 10:48 PM
Ian Woollard
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Default Cost of launch and laws of physics

Greg, it's mostly nothing to do with physics; it's economics. It's more
to do with the low market size right now; which in turn is to do with
the current high cost.

It's catch 22. The price is too high, so practically nobody goes.
Because nobody goes, the costs stay high (development costs don't
amortise away, unit costs stay high, production costs stay high.) It's
not that you don't need 10,000 people to go into space, it's just that
if you only send 4 rockets into space with those 10,000 people, then it
costs 2.7x more than if you send 16 rockets into space with, say, 15,000
people.

Basically, rockets are currently mostly built by hand, one off. That's
expensive. Production lines are cheaper. The Russians use more
production line techniques, and their rockets are about 1/4 the cost of
other people. (It has been very, very frequently suggested that low
wages are the reason for this, but people who have gone to Russia report
that it turns out that that only accounts for some, but not all of the
differences; Russian rockets are 1/2 the cost even allowing for this,
strangely enough the laws of physics are the same in Russia as elsewhere).

Physics definitely has a part to play though; it's just that that isn't
the dominant force that keeps the price high as it is right now.


  #9  
Old August 6th 03, 01:24 AM
Greg D. Moore \(Strider\)
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Default Cost of launch and laws of physics


"Greg Kuperberg" wrote in message
...

Think how much harder it is to build a car that goes 120 mph than a
bicycle that goes 12 mph. Now think how much harder it is build a jet
that goes 1,200 mph than a car. Now take it one step further and you've
got the difficulty of manned spaceflight. Of course doing any of these
in expendable, unmanned form is much easier, which is part of the reason
that most space rockets are expendable and unmanned.


Build or design? Design can be costly, but once designed, building is just
bending metal.

Compare how much manpower the Russians spend on producing a Soyuz or Proton
compared to say an American Atlas or Delta.

Then compare the infrastructure required to launch it.

Completely comparing salaries (since that's a tough one to compute) you'll
find if we build rockets the way the Russians do, they'd be cheaper by quite
a bit.



The flip side of this is that many of the CATS/RLV/X-Prize believers
don't seem to take the laws of physics very seriously. For example,
another Wired article quotes Gary Hudson as follows: "That leaves the most
frequently asked question about the Roton: wouldn't the rotor blades burn
off in the atmosphere? The remarkable - and counterintuitive - answer
is No." Given what happened to the space shuttle Columbia,
that is a fair question. Just calling the answer counterintuitive and
remarkable doesn't make it right.


No, but it IS right. The answer IS counterintuitive and remarkable. I
don't see where you argument is other than he didn't explain WHY it's
counterintuitive and remarkable. Which, given the context, he appears to
have done.

So, I have no clue what point you're making here.

Okay, I imagine that someone will tell me that I'm quoting out of context.
So here is the context:
--
/\ Greg Kuperberg (UC Davis)
/ \
\ / Visit the Math ArXiv Front at http://front.math.ucdavis.edu/
\/ * All the math that's fit to e-print *



  #10  
Old August 6th 03, 01:26 AM
Greg D. Moore \(Strider\)
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Posts: n/a
Default Cost of launch and laws of physics


"Greg Kuperberg" wrote in message
...
In article ,
Rand Simberg wrote:
Think how much harder it is to build a car that goes 120 mph than a
bicycle that goes 12 mph. Now think how much harder it is build a jet
that goes 1,200 mph than a car. Now take it one step further and you've
got the difficulty of manned spaceflight.


Funny thing is, it doesn't cost much more to to fly across country
than it does to drive, especially when one takes the full costs
(depreciation, etc.) into account.


But that's not the cost per pound, that's the cost per pound *per mile*.
Assuming 120 orbits, the space shuttle travels 3 million miles, which
at $10,000 per pound is 1/3 of a cent per pound per mile. That's only
3 to 10 times as high as a plane ticket, not two orders of magnitude.


No, but flying almost effectively becomes cost/lb. Cross-country is cheaper
than many shorter flights.

Obviously the driver for flight costs is NOT per/mile.



Heck, an LEO satellite might have 50,000 useful orbits, while Saturn is a
billion miles away. Space is already the cheapest form of transportation
counting your way. :-)

--
/\ Greg Kuperberg (UC Davis)
/ \
\ / Visit the Math ArXiv Front at http://front.math.ucdavis.edu/
\/ * All the math that's fit to e-print *



 




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