Orbiter shape.

"Dave O'Neill" wrote in message
om...
Rand Simberg wrote in message
link.net...
And right now, the key to low-cost lift is satisfying the vast market of
people who want to visit space.

There we go again, "vast market" - could we please be a little more
specific about what exactly you mean by "vast".

It might be "large" but not anything like large enough to fund the
development of vehicles which can operate at the necessary price
points.

Basic economics. As the cost for the product is lowered, demand soars. The
key to getting "large" demand is getting the cost "low enough".

Right now, the only private, paying passengers on spaceships have flown on
Soyuz for around $20 million per flight. If you drop that cost by an order
of magnitude ($2 million), the demand will go up. Drop it three orders of
magnitude ($20,000) and I think you've arrived at a cost low enough to
generate the demand that Rand is talking about (millions of people).

Of course, the devil is in the details. Just how much you can decrease the
cost of spaceflight is very much a topic of debate.

Jeff
--
Remove icky phrase from email address to get a valid address.

Jeff Findley wrote:


"Peter Fairbrother" wrote in message
...
my orbiters look more and more like the
Star-Trek's Enterprise. It's a saucer or capsule, with two jet engines on
stalks. The saucer is to re-enter, and the stalks extend after re-entry to
power the landing.

Even the engine room is there, to put the landing wheels in, and to act as
a
tail. The main deflector dish is absent though.

Am I going nuts? Is this actually a good design?

For science fiction I'd say yes. In real life, those extendable jet engines
add considerable weight, especially since they're only useful for landing.

The jet engines themselves are about 1 or 2% of the landing weight - l/d of
around 5, and thrust-to-weight of around 15 - and we need something to get a
controlled landing. I can't think of anything much better.

The long stalks should go, or course. The jet engines can pop up (I'm not
even sure they need to pop up, they might be okay in position during
re-entry) close to the top surface of the capsule. The wheels can deploy
through the bottom of the cone.


/---\
(o)/ \(o)
/ \
( )
\_ ________ __/
U U

Still needs fins though ...


(for directional stability. Really. Not just because they are cool).


--
Peter Fairbrother

"Jeff Findley" wrote in message ...

"Perplexed in Peoria" wrote in message
m...

And why are you assuming a capsule full of tourists. Why not a smaller
capsule with one tourist, or a slightly larger capsule with three. Is
there some major economy of scale here that I am missing?

Yes. It's the same economy of scale that drives airliner size bigger and
bigger. Soon we'll be seeing airliners bigger than the Boeing 747 flying.

By your argument, we ought to see hundreds of small planes replacing 747's
instead of bigger planes.

I'm sorry, you will have to be more explicit. I can imagine many different
economies of scale favoring large aircraft. For example, more passengers
per crew member, or more passengers per airport takeoff/landing slot. I don't
see how either of these applies to reentry capsules. One I have thought of
is the ratio of pressurized volume to pressure-containing surface area. But
increasing the volume decreases the curvature of the skin, so more reinforcement
might be needed. Therefore, it is not clear to me that there is an economy
of scale here.

I do see that the mass of the re-entry vehicle must be proportional to the
surface area of the re-entry vehicle. But assuming fixed vehicle geometry,
that seems to me to favor smaller reentry vehicles.

So, I don't yet understand your argument. There may well be economies,
but I don't know what they are.

Perplexed in Peoria wrote:

I do see that the mass of the re-entry vehicle must be proportional to the
surface area of the re-entry vehicle.

Then you see something that's not true. There is no such simple
relationship.

"Jeff Findley" wrote in message ...

"Dave O'Neill" wrote in message
om...
Rand Simberg wrote in message
link.net...
And right now, the key to low-cost lift is satisfying the vast market of
people who want to visit space.

There we go again, "vast market" - could we please be a little more
specific about what exactly you mean by "vast".

It might be "large" but not anything like large enough to fund the
development of vehicles which can operate at the necessary price
points.

Basic economics. As the cost for the product is lowered, demand soars. The
key to getting "large" demand is getting the cost "low enough".

Right now, the only private, paying passengers on spaceships have flown on
Soyuz for around $20 million per flight. If you drop that cost by an order
of magnitude ($2 million), the demand will go up. Drop it three orders of
magnitude ($20,000) and I think you've arrived at a cost low enough to
generate the demand that Rand is talking about (millions of people).

Of course, the devil is in the details. Just how much you can decrease the
cost of spaceflight is very much a topic of debate.

OK, just to have numbers to play with, assume a million paying passengers
per year and a ticket price of $20,000. Assume that $15,000 of that goes
to pay the tour guides, buy fuel, amortize the capital costs, and pay for
the liability insurance. Assume that the other $5000 goes to pay back the
investors for the R & D and development costs they incurred. Of this $5000
in development costs, assume that $3000 was tailored to the specific
requirements of the tourist industry, but that $2000 went into technological
innovations that will reduce the cost of all lift for all missions that
require lift (such as lunar colonization, SPS construction, and so on).

$2000 times 1 million passengers per year is $2 billion per year. Hmmm.
That is not peanuts. What is NASA's annual budget?

Of course, different numbers will give different results.

"Rand Simberg" wrote in message link.net...
Perplexed in Peoria wrote:

I do see that the mass of the re-entry vehicle must be proportional to the
surface area of the re-entry vehicle.

Then you see something that's not true. There is no such simple
relationship.

Gee thanks. That helped me a lot.

Perplexed in Peoria wrote:

I do see that the mass of the re-entry vehicle must be proportional to the
surface area of the re-entry vehicle.

Then you see something that's not true. There is no such simple
relationship.


Gee thanks. That helped me a lot.

Sorry, but I can't be expected to provide you with a course in entry
vehicle systems design and structures. There are many different factors
that determine vehicle mass besides surface area. Anything beyond that
is a treatise.

Perplexed in Peoria wrote:

$2000 times 1 million passengers per year is $2 billion per year. Hmmm.
That is not peanuts. What is NASA's annual budget?

About fifteen billion, of which over half is manned spaceflight.

Of course, different numbers will give different results.

Indeed.

Jeff Findley wrote:

"Dave O'Neill" wrote in message
om...
Rand Simberg wrote in message
link.net...
And right now, the key to low-cost lift is satisfying the vast market of
people who want to visit space.

There we go again, "vast market" - could we please be a little more
specific about what exactly you mean by "vast".

It might be "large" but not anything like large enough to fund the
development of vehicles which can operate at the necessary price
points.

Basic economics. As the cost for the product is lowered, demand soars. The
key to getting "large" demand is getting the cost "low enough".

No. The product also needs to be desirable.


Right now, the only private, paying passengers on spaceships have flown on
Soyuz for around $20 million per flight. If you drop that cost by an order
of magnitude ($2 million), the demand will go up. Drop it three orders of
magnitude ($20,000) and I think you've arrived at a cost low enough to
generate the demand that Rand is talking about (millions of people).


Millions of people is rather optimistic for *ANY* price range, much less $20000.

Of course, the devil is in the details. Just how much you can decrease the
cost of spaceflight is very much a topic of debate.

You also need to find a way to sustain teh desire to go there.


Jeff

--
Sander

+++ Out of cheese error +++

"Perplexed in Peoria" wrote in message m...

Those bucks will pay the development costs of a new generation of low
cost lift capability, as well as paying for the operational costs of the
fun part. Of course, those operational costs are just wasted money as
a step toward MY idea of progress, which, to be specific, is, say, a few
dozen large scale robotic sample-return missions to near earth asteroids.

Except for the fact that a reduction in launch costs might make it
*possible* for you to do those "few dozen large scale robotic
sample-return missions."

Yours is the classic "unmanned space" argument. Spending money on
human spaceflight will somehow take money away from your "unmanned"
missions. Okay, assuming we don't develop a new generation of low-cost
lift. How many large-scale robotic sample return missions can you
afford right now? Even one?

But perhaps the development costs of the amusement park ride will actually
help to achieve my goal.

Whether it does or not, rich people don't actually have an obligation
to spend *their* money in a way that enables *you* to achieve *your*
goals. If you aren't interested in human spaceflight, fine, but that
doesn't mean "amusement park rides" are somehow less worthy than your
radio-controlled toys.

Let us examine how. Hmmm. Maybe some of the
R & D for the tourism can be used in my program. Better rocket fuels, perhaps? Unlikely.

Better rocket fuels are not needed. (James Bond to the contrary.)

Maybe better engine design? Also unlikely to happen.

It's already happening. So, you ought to rethink your probabilities.

Operational
economies? But those are unlikely to translate to my very different mission
profile. But perhaps I can simply use some of the already developed and now
presumably-mass-produced hardware from the amusement ride for my mission.
Yeah. Thats the ticket!

Indeed.

I'll just strap the pieces-parts for my asteroid mission into the passenger
seat of the amusement ride, pay the (quite reasonable!) price for the SSTO
lift(s), and then assemble my mission in orbit!

That would be one way to do it, although the baggage compartment might
be more practical.