Cheap Access to Space

"Jim Relsh" wrote in message
.. .

I personally believe we won't see cheap (as in: every ordinary Joe can go
into space for the price of an expensive airplane ticket) access to space
for hundreds of years. Why? Because no matter how you view it we're still
using good-old fashioned momentum-transfer technology where we spit out
something in one direction and we and the rocket move in the other. Rocket
technology is and will most likely continue to be the easiest and best way
to get into space but due to the size and explosiveness of these vehicles
it will remain something of a hazardous experience making it impossible to
launch millions of people into space.

The size and explosiveness isn't orders of magnitude beyond an Airbus A380.
The freighter version has an option for a 356,000 L, 94,000 US gal, fuel
tank while the Saturn V first stage had a 209,000 US gal kerosene tank,
which is only about a factor of two bigger for explosiveness, and the Saturn
V first stage is pretty darn big!

Jeff
--
A clever person solves a problem.
A wise person avoids it. -- Einstein

On Dec 16, 4:04 pm, Fred J. McCall wrote:
Ian Parker wrote:

:
:Basically the viability of SPS depends on transportation.
:

It depends on much more than that. It depends on all sorts of
resource costs, development costs, etc.

:
:If you are saying that it will be enormously easier with asteroid
:material, you are of course right. What I was trying to work out was
:the establishment of a market of some description.
:

You can't work out the establishment of a market until you can talk
about costs and prices.

:
:I do not believe there will be enough tourists for a killer market.
:"Killer" here refers to the market that justifies the costs and drives
:it.
:

I don't believe we'll get to space at all if we're waiting for the
proverbial 'killer app'. Think 'small bites'.

The term "Killer App" (which I think is beyond silly), conjurs up
thoughts of the Hindenburg disaster when applying it to manned
commercial spaceflight.

Rand used the Grand Canyon as an analogy. I bet he has not read the
very popular book, "Death in the Grand Canyon". It basically speaks
about the fact that many people die in the GC due to not using common
sense.

Eric

On 17 Dec, 19:55, Eric Chomko wrote:
On Dec 16, 4:04 pm, Fred J. McCall wrote:





Ian Parker wrote:

:
:Basically the viability of SPS depends on transportation.
:

It depends on much more than that. It depends on all sorts of
resource costs, development costs, etc.

:
:If you are saying that it will be enormously easier with asteroid
:material, you are of course right. What I was trying to work out was
:the establishment of a market of some description.
:

You can't work out the establishment of a market until you can talk
about costs and prices.

:
:I do not believe there will be enough tourists for a killer market.
:"Killer" here refers to the market that justifies the costs and drives
:it.
:

I don't believe we'll get to space at all if we're waiting for the
proverbial 'killer app'. Think 'small bites'.

The term "Killer App" (which I think is beyond silly), conjurs up
thoughts of the Hindenburg disaster when applying it to manned
commercial spaceflight.

Rand used the Grand Canyon as an analogy. I bet he has not read the
very popular book, "Death in the Grand Canyon". It basically speaks
about the fact that many people die in the GC due to not using common
sense.

Eric- Hide quoted text -

Just one quick point of information "Killer app" was coined in
computer science for the application that would pay for a new
generation of computers, operating system etc. Perhaps though you are
right, it is a silly term.

The question of risk in space travel is not however a trivial point.
We were also told the Shuttle would be "safe". It wasn't. I think
there may well be a moral question here. If you are a professional
astronaut you take risks, you have to to get the job done. If you are
a tourist you are risking your life for no really good purpose.

My experience of tourism and risk is of going round an empty Krak (and
other places like Ugarit and Palmyra). It was nice. I could just trail
behind everyone else and get clear shots with my camera.. There the
risk was very low - only the CIA claims there was any at all. Krak des
Chevaliers is every bit as magnificent in its way as the grand canyon.
But people don't go there.

I am inclined to feel thast when this question of risk comes up people
will back off. I am not sure in my own mind how much tourism is to be
encouraged. OK in a free society you cannot stop people, but this
consideration is always at the back of my mind.


- Ian Parker

Ian Parker wrote:
:
:If you are
:a tourist you are risking your life for no really good purpose.
:

And yet this doesn't stop people from engaging in mountain climbing,
etc.


--
"Rule Number One for Slayers - Don't die."
-- Buffy, the Vampire Slayer

On Dec 16, 1:20 am, Fred J. McCall wrote:
wrote:

:
:Now for my proposal.
:
:I propose, -decrease- the payload fraction, thus increasing the mass
f the vehicle, on purpose. Why you might ask? Because the first stage
:is not reusable in the above system. But if the first stage is a
:rocket-plane that flies to above 40 km and then deploys a 2-stage
:rocket system that boosts to orbit, instead of a throw-away system,
:then it is true the weight of the wings -adds- to the total weight of
:the system, but the first stage, which is the most massive part of the
:vehicle, becomes reusable.
:

Your proposal amounts to the proposition that reusable vehicles are
cheaper than expendable vehicles, assuming they cost no more to build
per pound, require no maintenance, and are good for a relatively large
number of flights on that basis.

The problem is

1) Reusable vehicles are going to cost more per pound than
expendables.

2) They're probably going to have significant maintenance costs spread
over their flight lifetime.

3) If you want them to last for a long time the prior two costs
increase even further.

The Space Shuttle has a big, costly reusable piece. Under your model
it ought to lead to significant cost savings. It doesn't. Examining
why it doesn't will show you where some of the flaws in your thinking
are.

Interesting. Most of us look at the large ET--and the
solids (about the same cost whether they are expendable
or reusable)--and figure that the system is pretty hopeless
from the low-cost point of view. However, this may be an
important factor for why the large reusable piece is not
particularly cost-effective. I suspect that once you have
abandoned cost discipline, all components end up being
rather wasteful from the cost point of view. A case in
point would be the lack of design options for challenging
the chosen TPS.

Another factor was the SSME, which used a lot of
material rejected for the RL10 because of hydrogen
embrittlement--not to mention a spindly shaft going
through several stages of instability getting up to speed,
plus pressure gradients running from hot to cold, rather
than vice versa. This was not a good starting design
for a reusable engine.

I remember being chastised by some NASA folks
for calling the RL10 reusable, based upon hard test
data. No. The RL10 by definition was expendable;
the SSME by definition was reusable.

Just invoking the word reusability does not ensure
low-costs.

Len

--
"The reasonable man adapts himself to the world; the unreasonable
man persists in trying to adapt the world to himself. Therefore,
all progress depends on the unreasonable man."
--George Bernard Shaw

On Sun, 16 Dec 2007 13:46:00 +0100, "Jim Relsh" wrote:


wrote in message
...
There has been lots of interest in Scramjets because of their
potential to lower the cost of access to space, or Single Stage to
Orbit as a means of lowering cost of access to space.

I personally believe we won't see cheap (as in: every ordinary Joe can go
into space for the price of an expensive airplane ticket) access to space
for hundreds of years. Why? Because no matter how you view it we're still
using good-old fashioned momentum-transfer technology where we spit out
something in one direction and we and the rocket move in the other. Rocket
technology is and will most likely continue to be the easiest and best way
to get into space but due to the size and explosiveness of these vehicles it
will remain something of a hazardous experience making it impossible to
launch millions of people into space.


"Size and explosiveness of the vehicles"?

The typical rocket-powered space launch vehicle has a dry weight rather
less than that of a typical jet airliner. Even the Space Shuttle only
comes in at 282 tons with the ET and RSRMs, comparable to a 747-400 or
an A-380, and the Shuttle is the behemoth of the launcher world. An
Atlas 552 comes in at 48 tons dry, which is less than a 737 or A-310.

The gross weight is rather more, but not hugely so and in any event
that's all fuel. Fuel is cheap; even a shuttle's worth of fuel should
only cost ~$3.2 million, which divided by the hypothetical capacity of
an all-passenger shuttle would only come to $40K/ticket. A bit more
than the usual airline ticket, but plausible for an Ordinary Joe's
once-in-a-lifetime dream vacation, and again the Shuttle is a bloated
monstrosity even by today's standards so that's an upper limit.

Related to this, the ammount of payload you can deliver to orbit per
ton of vehicle is rather less than a jet airliner can manage. But
again, not by so much as to make tickets impossibly expensive.


As for explosiveness, well, OK, the Shuttle does have those pesky solid
rocket motors. So look at a no-solids Atlas. There's seventy-five tons
of kerosene in there. I'd wager you have flown on airplanes with more
than seventy-five tons of kerosene on board, without fear of perishing
in a sudden, random explosion. It's true that the rocket also has a
whole lot of liquid oxygen, but liquid oxygen isn't explosive or even
incendiary unless it has fuel to match, and if your fuel supply is
seventy-five tons of kerosene that's plenty for a vehicle-immolating
fireball just with ordinary air as your oxidizer.

So how is it that seventy-five tons of kerosene is somehow inherently
more explosive in a rocket vehicle than it is in a jet?


If a rocket crashes, it will probably "explode". Big-ass fireball, at
very least. But the same tends to be true of jet airplanes, and in
either case the explosion is almost always A: the result, not the cause,
of the crash, and B: irrelevant because the vehicle and payload were
already lost on account of being smashed into the ground at high speed
or something like that.


Rocket-powered space launch vehicles are not terribly large and they are
not terribly "explosive". They are, at present, very expensive and very
unreliable, but that's not the same thing. And more importantly, the
cost and the unreliability are in no way intrinsic to rocket propulsion.


--
*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 *

John Schilling wrote:
On Sun, 16 Dec 2007 13:46:00 +0100, "Jim Relsh" wrote:

wrote in message
...
There has been lots of interest in Scramjets because of their
potential to lower the cost of access to space, or Single Stage to
Orbit as a means of lowering cost of access to space.

I personally believe we won't see cheap (as in: every ordinary Joe can go
into space for the price of an expensive airplane ticket) access to space
for hundreds of years. Why? Because no matter how you view it we're still
using good-old fashioned momentum-transfer technology where we spit out
something in one direction and we and the rocket move in the other. Rocket
technology is and will most likely continue to be the easiest and best way
to get into space but due to the size and explosiveness of these vehicles it
will remain something of a hazardous experience making it impossible to
launch millions of people into space.


"Size and explosiveness of the vehicles"?

The typical rocket-powered space launch vehicle has a dry weight rather
less than that of a typical jet airliner. Even the Space Shuttle only
comes in at 282 tons with the ET and RSRMs, comparable to a 747-400 or
an A-380, and the Shuttle is the behemoth of the launcher world. An
Atlas 552 comes in at 48 tons dry, which is less than a 737 or A-310.

The gross weight is rather more, but not hugely so and in any event
that's all fuel. Fuel is cheap; even a shuttle's worth of fuel should
only cost ~$3.2 million, which divided by the hypothetical capacity of
an all-passenger shuttle would only come to $40K/ticket. A bit more
than the usual airline ticket, but plausible for an Ordinary Joe's
once-in-a-lifetime dream vacation, and again the Shuttle is a bloated
monstrosity even by today's standards so that's an upper limit.

Related to this, the ammount of payload you can deliver to orbit per
ton of vehicle is rather less than a jet airliner can manage. But
again, not by so much as to make tickets impossibly expensive.


As for explosiveness, well, OK, the Shuttle does have those pesky solid
rocket motors. So look at a no-solids Atlas. There's seventy-five tons
of kerosene in there. I'd wager you have flown on airplanes with more
than seventy-five tons of kerosene on board, without fear of perishing
in a sudden, random explosion. It's true that the rocket also has a
whole lot of liquid oxygen, but liquid oxygen isn't explosive or even
incendiary unless it has fuel to match, and if your fuel supply is
seventy-five tons of kerosene that's plenty for a vehicle-immolating
fireball just with ordinary air as your oxidizer.

So how is it that seventy-five tons of kerosene is somehow inherently
more explosive in a rocket vehicle than it is in a jet?


If a rocket crashes, it will probably "explode". Big-ass fireball, at
very least. But the same tends to be true of jet airplanes, and in
either case the explosion is almost always A: the result, not the cause,
of the crash, and B: irrelevant because the vehicle and payload were
already lost on account of being smashed into the ground at high speed
or something like that.


Rocket-powered space launch vehicles are not terribly large and they are
not terribly "explosive". They are, at present, very expensive and very
unreliable, but that's not the same thing. And more importantly, the
cost and the unreliability are in no way intrinsic to rocket propulsion.

One of the benefits of hydrogen is that you don't need any escape
motors, just a blast shield, and well designed seat and vehicle.

The hydrogen fireball will blow you right out of it, and then blow
itself out. The hydrogen core stage itself is a great kick motor.

One less thing to worry about!

Len wrote:
:
:Another factor was the SSME, which used a lot of
:material rejected for the RL10 because of hydrogen
:embrittlement--not to mention a spindly shaft going
:through several stages of instability getting up to speed,
lus pressure gradients running from hot to cold, rather
:than vice versa. This was not a good starting design
:for a reusable engine.
:
:I remember being chastised by some NASA folks
:for calling the RL10 reusable, based upon hard test
:data. No. The RL10 by definition was expendable;
:the SSME by definition was reusable.
:
:Just invoking the word reusability does not ensure
:low-costs.
:

Exactly. Running hardware at 100% of design (or beyond) as routine
operation almost guarantees that a reusable vehicle will be quite
expensive (because of teardown, overhaul, and inspection costs).


--
"The reasonable man adapts himself to the world; the unreasonable
man persists in trying to adapt the world to himself. Therefore,
all progress depends on the unreasonable man."
--George Bernard Shaw

At less than a tenth the NASA cost per LEO or GSO kg, China is CATS.

Of course China is going to charge outsiders a whole lot more than
whatever it's costing themselves.
- Brad Guth


On Dec 14, 11:23 pm, wrote:
There has been lots of interest in Scramjets because of their
potential to lower the cost of access to space, or Single Stage to
Orbit as a means of lowering cost of access to space.

Back in 1972, it was estimated that the Space Shuttle would cost as
little as $455 per kg. In 2007 dollars, this works out to $2,188.05
per kg. And that was considered good. Below, I outline my theory as to
how we can achieve $600 per kg today, which would work out to $125 in
2007 dollars or better than the space shuttle was supposed to be.

If you can get costs below $600 per kg in today's dollars, you can
launch 25,000 kg of payload for $15 million and thus sell 20 tickets
to space for $15 million, or tickets are for sale at $750,000 per
ticket. That seems reasonable. (The Space Shuttle has a payload of
approximately 25,000 kg).

I will assume the first stage goes straight up and has an imparted
acceleration of 3 g's, e.g. an actual acceleration of 2 g's. I will
also assume it takes 9700 m/s to reach orbit from the ground (orbital
velocity is somewhat less but we must contribute both kinetic and
potential energy to achieve a circular orbit). I will also assume we
have a payload of 25,000 kg and the fuels used are liquid hydrogen
(LH2) and liquid oxygen (LOX). I assume hydrogen costs $3.00 per kg
and oxygen costs $0.20 per kg. These seem reasonable.

Finally I make one small blunder: the cost of the vehicle without fuel
is just $100 times the weight in kilograms. This seems reasonable if
it is made of aluminum alloy, but in practice it takes a lot of energy
to machine rocket parts from raw materials, and all this energy costs
money. Nevertheless $100/kg is a ball-park figure (note this low cost
precludes the use of titanium, baring any new technologies. Also we
might need to circulate a fluid throughout the skin of the first stage
to keep it from melting).

First, let's look at a 3-stage throw-away system for comparison with
my proposal.

A typical rocket is 71% propellant and has 15% payload, e.g. is 14%
empty weight. This corresponds with a mass ratio of 3.45 which seems
reasonable.

Stage 1 : 71% propellant, 15% payload, 14% empty. Imparted delta V is
4330 m/s but only 2881.2 m/s is realized due to gravity losses (we're
flying straight up). We assumed an exaust velocity of 3500 m/s which
is reasonable for LH2-LOX at sea level.

Stage 2 : 71% propellant, 15% payload, 14% empty. A delta-V of 5447 m/
s is realized. We assume an exaust velocity of 4400 m/s which is
reasonable for LH2-LOX in vacuum.

Stage 3 :1373 m/s is needed to reach our 9700 m/s figure. This leads
to a needed mass ratio of 1.366 e.g. 26.8% propellant, 14% empty,
59.2% payload.

Now using this figure as a baseline, we will see how my proposal
stands. The payload is
0.15 * 0.15 * 0.592 = 1.332%. Since we state that we have a payload of
25,000 kg, we deduce the vehicle must have a mass of 1,876,877 kg at
liftoff.

Let's get a minimum estimate of how much it costs, though. To do this,
we take the liftoff mass of 1,876,877 kg and multiply by 14% to get
the empty weight of just the first stage. At $100 / kg, just the first
stage costs $26,276,276.

Using this method, we can get to space, but it costs over $25 million
to reach orbit. That is, it costs over $1000 per kg to reach orbit.

Now for my proposal.

I propose, -decrease- the payload fraction, thus increasing the mass
of the vehicle, on purpose. Why you might ask? Because the first stage
is not reusable in the above system. But if the first stage is a
rocket-plane that flies to above 40 km and then deploys a 2-stage
rocket system that boosts to orbit, instead of a throw-away system,
then it is true the weight of the wings -adds- to the total weight of
the system, but the first stage, which is the most massive part of the
vehicle, becomes reusable.

I assume the first stage is a rocket-plane with an empty mass of 42%
(including wings, ball-park what the Concord's empty weight is). We
still want the rocket-plane to have 15% payload, and this leaves us
with only 43% rocket propellant. Using an exaust velocity of 3500 m/s
again, we see the first stage can impart only a delta-V of 1967 m/s.

Now we are taking off vertically (the first-stage lands horizontally).
1967 m/s is the vertical velocity we'd achieve if there were no
gravity losses. It's mach 5.73 at sea level, but we'll be over 40 km
in altitude by this point, so "hypersonic" stage separation is a non-
issue. Again we assume an imparted acceleration of 3 g's (29.4 m/s^2).
The first stage boost thus lasts only 66.9 seconds.

Actual velocity achieved will be 1311.24 m/s (2 g's times 66.9
seconds). We achieve an altitude of 0.5 * 2g * t * t = 43861 m or just
over 40 km.

We are cruising upwords at 1311.24 m/s -- say 1300 m/s -- at 43,861 m
altitude. That is 143,901 ft. Way high up.

Now to achieve orbit, we need a delta-V of 9700 m/s. 9700 - 1300 =
8400 m/s.

That's where the space plane deploys its 2-stage rocket system. In 2
stages we must achieve a delta-V of 8400 m/s.

Stage 2 : 71% propellant, 15% payload, 14% empty weight. Using an
exaust velocity of 4400 m/s (in vacuum), we can achieve a delta-V 5447
m/s via Stage 2..

Stage 3 : to reach 9700 m/s we need a delta-V of 2953 m/s. That is, a
mass ratio of 1.96 or 49%. If it's 14% empty weight, we can have a
payload of 37%.

Putting it all together: 0.37 * 0.15 * 0.15 = 0.008325. That is to
say, we now have a payload fraction that has been reduced, to only
0.8325%. That sounds low, it's certainly lower than the payload
fraction of the disposable 3-stage rocket described above.

3,003,003 kg is the take-off weight needed for 25,000 kg to reach
orbit. It's considerably more than the weight of the 3-stage throw-
away (disposable) rocket system, but, let's see how the cost compares!

3.003003e6 * 0.42 = 1261261.26 x $100/kg = $126,126,126 (Not bad!
E.g. $ 504,505 / flight at 250 flights)

That is to say, the first stage "reusable" space plane costs $126
million. We amortize it over 250 flights, assuming it is good for that
many flights. Dividing $126 million by 250, we find the cost of the
first stage is only about $500,000 per flight. Compare that to the $25
million cost of the disposable first stage!

3.003003e6 * 0.15 * 0.14 = 63063.063 x $100/kg = $ 6,306,306.3
3.003003e6 * 0.15 * 0.15 * 0.14 = 9459.45945 x $100/kg = $
945,945.945
Total SHIP cost per flight: 504505 + 6306306.3 + 945945.945 =
$7,756,757.245
Dividing by 25,000 kg we find the ship cost is $310/kg

Propellant cost.
3.003003e6 * 0.43 = 1 291 291.29 kg
3.003003e6 * 0.15 * 0.71 = 319 819.8195 kg
3.003003e6 * 0.15 * 0.15 * 0.49 = 33 108.108075 kg

Total propellant: 1291291.29 + 319819.8195 + 33108.108075 = 1 644 219
kg
LH2 : 1644219 * 11800 / 81614 = 237726 * 3.00 USD = $ 713178.0
LOX : 1644219 * 69814 / 81614 = 1406493 * 0.20 USD = $ 281298.6

Total propellant cost: $994476.6

Total mission cost: 994476.6 + 7756757.245 = $ 8 751 233.845
E.g. $350 / kg

Thus, if amortizing over 250 flights is reasonable, e.g. if we can
actually find 250 customers that need to launch 25,000 kg into space
for a mission cost of $15,000,000 (e.g. ticket price of $750,000 for
20 tourists on a 3-day mission to space), then including fuel -and-
the cost of the disposable vehicle, we arrive at a total mission cost
of around $9.0 million.

But there are other costs like human salaries and so on, and providing
the payload itself, and profit, so we will round this figure up to
$15.0 million per mission.

Compare this cost to the first-stage cost of $25.0 million for a throw-
away system. Thus, I have shown that a reusable first-stage, despite
having a heavy wing weight, can substantially reduce the per-mission
and per-kg payload cost.

Even though the payload fraction is substantially reduced, and -
without- using single-stage-to-orbit or scramjets, we have found a way
to lower the cost of access to space, within the model used (e.g. $100/
kg empty cost etc.), to just $600 / kg which is marketable.

Anyone care to comment or check my numbers? Your feedback is
appreciated!

On 17 Dec, 22:02, Fred J. McCall wrote:
Ian Parker wrote:

:
:If you are
:a tourist you are risking your life for no really good purpose.
:

And yet this doesn't stop people from engaging in mountain climbing,
etc.

--
"Rule Number One for Slayers - Don't die."
-- Buffy, the Vampire Slayer

In point of fact a great deal of research has been done by
psychologists on risk perception. Basically if you feel you are in
control of a risk you are more inclined to take it. You are in control
(psychlogically speaking) when you are rock climbing or driving a car
fast. If you are not driving you are not in control of the risk. Quite
often people who like driving fast don't like being driven fast.

There is a question of safety requirements. If you are launcing smart
pebbles, you need to worry about safety less than for anything else.
You simply accept a level of loss for near identical components.
Tourism would require stringent safety requirements and these
requirements might conflict.


- Ian Parker