Cheap Realistic Space Flight

(Serg) writes:

"Charles Talleyrand" wrote in message
...

I'm trying to imgaine cheap space flight. I'd also like to see it
sooner rather than later. Given this I believe we are limited to
chemical rockets.

If you are talking about cheap, but politically unrealistic
spaceflight, I don't think anything could beat Orion. More politically
plausible would be NTR , I think still cheaper then chemical (without
development cost).

As currently conceived, NTR doesn't fly --- literally. The reactor power
densities are so low that the thrust-to-weight ratio is less than unity;
hence, an NTR cannot even lift its _own_ weight in a 1 gee field, let alone
a spacecraft! One has to go to an "advanced" design like the DUMBO micro-
structured heat exchanger that can handle power-densities at least an order
of magnitude higher than current solid-core or "TRIGA pellet" designs.

The "Nuclear Light-Bulb" gaseous-core reactor design would be more
effective still --- if one could just figure out how to keep the "light bulb"
envelope from melting, while still efficiently transferring the radiative heat
to the propellant. (Sadly, Hydrogen tends to be rather more transparent than
most "light bulb" materials, so there is a slight technical problem in that
the "light bulb" wants to melt more than the propellant wants to get hot...
Also, I expect gas-core nuclear rockets to be at _least_ an order of magnitude
more Politically Incorrect than RTG-powered space probes --- which are already
routinely picketed by Greenpeace and the Union of Concerned "Scientists"...)


-- Gordon D. Pusch

perl -e '$_ = \n"; s/NO\.//; s/SPAM\.//; print;'

Charles Talleyrand wrote:
I'm trying to imgaine cheap space flight. I'd also like to see it
sooner rather than later. Given this I believe we are limited to
chemical rockets.

What's the cheapest cost to orbit a chemical rocket is likely to
yield in the next fifty years? Will we see $100/pound to orbit?
How about $10/pound? And what underlying technology will
this rocket use?

Note: Please avoid the use of wormholes and unobtanium. Please
don't say "carbon nanotubes will solve everything" unless you also
believe that we will build 50,000 lbs structures in carbon nanotubes
sometime in the next 50 years. We're looking reasonably far into
the future (50 years or less) but trying to limit ourselves to chemical
rockets and things that can actually be built and used.



This is frequently discussed on sci.space.policy.

Some believe if rocket engines were massed produced economies of scale
would make launch expense much less.

They are hoping the X-prize contenders will open a new industry of space
tourism, and that many would pay to enjoy sub orbital flight into near
earth space just as people paid to enjoy rides with barn stormers in the
early days of aviation.

It's argued that a free market could make rockets common just as it has
done for motor cars, airplanes, and computers.

If rocket engines become very affordable, the expense may be dominated
by fuel. I believe your fuel to payload ratio is e^(Vf/Ve) where Vf is
final velocity and Ve is exhaust velocity. IIRC 4 km/sec is good exhaust
velocity for chemical rockets. And 8 km/sec is an orbital velocity. So
e^(8/4) = e^2 = about 7.4. So you'd need more than 7 times the mass of
your payload in fuel.

Another obstacle is government regulation. I can see the need for
regulation but some sci.spacers argue that existing regulations will
smother the space tourism industry before it's born.

--
Hop David
http://clowder.net/hop/index.html

Case in point --
Government Regulations in the aftermath of September 11, 2001.

As applied to experimental rocketry, some of the media (notably in the EAA
websites) are asserting that tighter regulations of fuel canisters such as
the Estes model rockets may well cause the end of model rocketry.

--
Leonard C Robinson
"The Historian Remembers, and speculates on what might have been.
"The Visionary Remembers, and speculates on what may yet be."

In article , says...
What's the cheapest cost to orbit a chemical rocket is likely to
yield in the next fifty years? Will we see $100/pound to orbit?
How about $10/pound? And what underlying technology will
this rocket use?


NASA was talking a few years ago of getting it to $1000/pound in the
future. No way will they achieve it soon.

But you need to specify more details.

Say it costs you $X to develop the rockets
Say you build a launch pad for $Y
Say each rocket costs $Z
Say each rocket carries P pounds

and use it to fire N rockets

Then your cost per rocket per pound = (x+y+z) * P / N

N at present is probably the most disappointing figure.

--
I hope that God's behaviour improves in the future?

Bernardz wrote:
In article , says...

What's the cheapest cost to orbit a chemical rocket is likely to
yield in the next fifty years? Will we see $100/pound to orbit?
How about $10/pound? And what underlying technology will
this rocket use?



NASA was talking a few years ago of getting it to $1000/pound in the
future. No way will they achieve it soon.

But you need to specify more details.

Say it costs you $X to develop the rockets
Say you build a launch pad for $Y
Say each rocket costs $Z
Say each rocket carries P pounds

and use it to fire N rockets

Then your cost per rocket per pound = (x+y+z) * P / N

N at present is probably the most disappointing figure.

try
(X + Y + Z*N) / (P*N)
or
(X+Y+Z)/P for the first rocket
Z/P for each additional
X and Y will realistically far exceed Z.

In article ,
says...
Bernardz wrote:
In article , says...

What's the cheapest cost to orbit a chemical rocket is likely to
yield in the next fifty years? Will we see $100/pound to orbit?
How about $10/pound? And what underlying technology will
this rocket use?



NASA was talking a few years ago of getting it to $1000/pound in the
future. No way will they achieve it soon.

But you need to specify more details.

Say it costs you $X to develop the rockets
Say you build a launch pad for $Y
Say each rocket costs $Z
Say each rocket carries P pounds

and use it to fire N rockets

Then your cost per rocket per pound = (x+y+z) * P / N

N at present is probably the most disappointing figure.

try
(X + Y + Z*N) / (P*N)

You are of course correct.

or
(X+Y+Z)/P for the first rocket
Z/P for each additional
X and Y will realistically far exceed Z.


Depends on whether you write off X and Y or whether you depreciate it.

In real terms I would expect that the cost of the rocket will be a minor
cost compared to the development costs.





--
I hope that God's behaviour improves in the future?

JRS: In article MPG.1a0bc43169ef91be989695@news, seen in
news:rec.arts.sf.science, Bernardz
posted at Fri, 31 Oct 2003 00:58:59 :-
In article , says...
What's the cheapest cost to orbit a chemical rocket is likely to
yield in the next fifty years? Will we see $100/pound to orbit?
How about $10/pound? And what underlying technology will
this rocket use?


NASA was talking a few years ago of getting it to $1000/pound in the
future. No way will they achieve it soon.


NASA cannot do it, but the US Government might.

The Dollar is currently the least valuable unit of the major Western
countries, and, like almost all currencies, its value in real terms
(technological equipment apart) continues to fall.

There is very little in the UK that is normally bought as an individual
purchase for which the per-item cost is not a multiple of 5 pence
(except for cases such as £x.99); we hardly need our coppers now.
Presumably the cent is in a similar situation to the penny.

So it would be logical, in the foreseeable future, to redenominate the
Dollar; a new Dollar worth ten old Dollars, with the loss of present
coins under 10c, would be convenient (the change might be as popular as
changing to metric; but the situation needs to be faced. Granted, the
Italians managed with their lire).

That would, of course, at a stroke reduce NASA's Dollar costs tenfold.

FYI, the Soviets achieved a similar redenomination, probably by a factor
of 100, almost overnight, IIRC.


ISTM that there is too much stress on CATS, and more overt attention
should be paid to RATS. Where RATS lead(s), CATS follow(s).

R = Reliable.

--
© John Stockton, Surrey, UK. Turnpike v4.00 MIME. ©
Web URL:http://www.merlyn.demon.co.uk/ - FAQqish topics, acronyms & links;
some Astro stuff via astro.htm, gravity0.htm; quotes.htm; pascal.htm; &c, &c.
No Encoding. Quotes before replies. Snip well. Write clearly. Don't Mail News.

What's the cheapest cost to orbit a chemical rocket is likely to
yield in the next fifty years? BRBR


The trouble is that there's no simple answer. "It depends" sounds like a cop
out, but it's true. The market demand, and thus the flight rate, are as or
more important than the vehicle design and operation in determining cost per
pound to orbit of the system. For example, the Pegagus guys say their cost
would be about 1/3 what it is now if the flight rate was 4x higher, so the
fixed infrastructure could be spread over more flights.

Assuming a robust market, the likely low-cost approach is a mix of dumb simple
ELVs for medium and heavy lift and TSTO RLVs for specialty missions like
shuttling humans to LEO. (An SSTO RLV should be cheaper to operate but will
take more upfront investment than TSTO, and again, the market wil ldetermine
which approach would produce the lowest cost.)

Confusing enough? It gets a lot worse in practice


Matt Bille
)
OPINIONS IN ALL POSTS ARE SOLELY THOSE OF THE AUTHOR

"Charles Talleyrand" writes:

I'm trying to imgaine cheap space flight. I'd also like to see it
sooner rather than later. Given this I believe we are limited to
chemical rockets.

What's the cheapest cost to orbit a chemical rocket is likely to
yield in the next fifty years? Will we see $100/pound to orbit?
How about $10/pound? And what underlying technology will
this rocket use?


$10/pound is close to the ultimate limit, barring miracle tech,
of three times the fuel/energy cost. That's where the airline
industry has stabilized after a hundred years of manned airline
flight, and the same economic logic seems to apply.

But it took a hundred years for the airline industry to get where
it is today, and anyone suggesting we've already had fifty years
of actual progress in space launch will be laughed at. Fifty
years from now, we'll probably still be at the $100/pound level
and still trying to figure out the ultimate best way to run the
show.

The underlying technology will be, well, rocketry. Pump liquid
oxygen and probably something hydrocarbonish into a metal chamber,
burn same, and exhaust through a converging/diverging nozzle.
Use some fraction of the propellant that hasn't been burnt yet
to A: regeneratively cool the whole assembly and B: run the fuel
pumps. This works as well as anything that can be expected to;
it converts 95+% of the energy content of the propellant into
kinetic energy at a prodigious rate in an extremely compact
system.

There may be some use of airbreathing engines and wings to augment
rocketry during the early part of the mission, especially if the
best system turns out to be two-staged. I strongly doubt that this
will ultimately be the best, but it makes for an easier introduction
to the field and may still be state-of-the-art in 2053 even if I
expect it to be quaintly archaic by 2103.

The only advanced technology at less than the miracle level that
will really change things is materials science; better structural
materials and better thermal protection systems will be seriously
helpful. What is actually necessary, is better systems engineering,
and that's mostly not a technology issue.


--
*John Schilling * "Anything worth doing, *
*Member:AIAA,NRA,ACLU,SAS,LP * is worth doing for money" *
*Chief Scientist & General Partner * -13th Rule of Acquisition *
*White Elephant Research, LLC * "There is no substitute *
* for success" *
*661-951-9107 or 661-275-6795 * -58th Rule of Acquisition *

In article ,
John Schilling wrote:
$10/pound is close to the ultimate limit, barring miracle tech,
of three times the fuel/energy cost. That's where the airline
industry has stabilized after a hundred years of manned airline
flight, and the same economic logic seems to apply.

Yes and no. Max Hunter pointed out that we ought to be able to do better
than jet aircraft. Most of the operating costs do not scale with fuel
load -- "the multipliers are on the *empty* weight, and then add fuel" --
and we are so much more fuel-intensive that fuel ought to dominate our
ultimate-limit costs more.

However, this changes John's conclusion only by perhaps a factor of 2.
--
MOST launched 30 June; first light, 29 July; 5arcsec | Henry Spencer
pointing, 10 Sept; first science, early Oct; all well. |