top ten reasons there'll be faster progress

: Joe Strout
: But maybe I'm making an assumption here, which is that the flight
: profile needed to get a longer hang time must necessarily evolve towards
: an orbital profile. I suppose that, in principle, you could instead
: just throw yourself higher straight up, without accelerating
: horizontally. My intuition is that that would be a stupid approach,
: since (1) it would mean a much hotter reentry, and (2) you're not taking
: advantage of the curvature of the Earth to increase your hang time.

I don't think the curvature thing is significant until you get fairly
long horizontal distances, some hundreds of miles. Can somebody supply
numbers? Which brings up a reason to go straight up (or sort-of-mostly)
for longer hang times, and that's the fact that it seems simplest to
take off and land at the same facility, both for the vendor, and so the
customers don't have to get back to the starting point.

Of course, a) it could be sold as a package, or the return handled more
conventionally (though that makes the craft and support infrastructure
more complicated), and b) it could be exploited as a transition to
offering extremely fast trips to a few locations; then the longer trips
you support, the more cities you can reach, and that's an incremental
approach to near-orbit. Imagine new-york-to-tokyo suborbital commuting
service. Concorde, schmoncorde.

So it looks like a mixed bag; I doubt all the factors could be
predicted by market research, but it'd be interesting.


Wayne Throop http://sheol.org/throopw

(Henry Spencer) wrote:

Moreover, substantial suborbital operations will create the beginnings of
a supplier base for commercially-priced (as opposed to government-priced)
engines, guidance, materials, safety systems, etc. That will make it a
good deal easier to *build* an orbital vehicle, even if the design has to
be entirely new.

It'll be interesting to see how far that effect goes - as most
potential operators seem to be mostly 'rolling their own'. For the
long term health of the industry, we need to follow the same path
virtually every other transport industry has followed - airframe
manufacturers need to be seperate from operators.

D.
--
Touch-twice life. Eat. Drink. Laugh.

-Resolved: To be more temperate in my postings.
Oct 5th, 2004 JDL

But what about the point that, in a competitive market, those who offer
a longer microgravity time are offering a better product? If company A
gives you 5 minutes of weightlessness for $1X, and company B gives you
10 minutes of weightlessness for $1.5X, then many customers would prefer
to fly company B, assuming they have $1.5X available, I would think.

It is far from clear to me.

Is the appeal just saying "I went to space"?

Or is it more like "I was able to do acrobatic tricks a, b, and c, and
boy I hope I get to fly again so I can try d and e"? And if so, is
one ten minute flight better or worse than two 5 minute flights?

Or is "I went to space" for first time customers and "I want to do x
and y in space" for repeat customers? If so, what is the breakdown
between first time and repeat?

But maybe I'm making an assumption here, which is that the flight
profile needed to get a longer hang time must necessarily evolve towards
an orbital profile. I suppose that, in principle, you could instead
just throw yourself higher straight up

As long as there is a growth in delta V, you are still headed towards
orbital. The flight profile is a more minor aspect of vehicle design
than things like thrust, isp, and tank size.

There is a potential intermediate step at about 85% of the delta V of
orbital - passenger/package service to the other side of the globe -
but there's a big gap between SpaceShipTwo and that 85% craft.

Moreover, substantial suborbital operations will create the beginnings of
a supplier base for commercially-priced (as opposed to government-priced)
engines, guidance, materials, safety systems, etc.

It'll be interesting to see how far that effect goes - as most
potential operators seem to be mostly 'rolling their own'

Even at this early stage, there is some evidence that operators are
not just rolling their own. The most obvious example is Virgin:

Operator = Virgin Galactic
Vehicle = Scaled Composites
Engine = SpaceDev

I expect this kind of supplier base (I guess we call it "vertical
non-integration") to be more prominent if/when/as the industry starts
to grow. Having the engine company separate from the vehicle company
is more likely to produce benefits if more than one vehicle company is
buying engines from them. And it might take a while for that
situation to develop.

For that matter, even if the engines, guidance, materials, safety
systems, etc are developed in-house, they still might be available for
a future orbital craft. Either because their maker isn't trying for
orbital and is glad to sell to someone who is, or because the orbital
craft in question is their own, or because they don't mind
coopetition.

On 27 Jun 2006 19:11:22 -0400, in a place far, far away, Jim Kingdon
made the phosphor on my monitor glow in such a way
as to indicate that:

Moreover, substantial suborbital operations will create the beginnings of
a supplier base for commercially-priced (as opposed to government-priced)
engines, guidance, materials, safety systems, etc.

It'll be interesting to see how far that effect goes - as most
potential operators seem to be mostly 'rolling their own'

Even at this early stage, there is some evidence that operators are
not just rolling their own. The most obvious example is Virgin:

Operator = Virgin Galactic
Vehicle = Scaled Composites
Engine = SpaceDev

While I agree that this trend seems to be occuring, Scaled is not
using SpaceDev for their SS2 propulsion. They seem to be developing
it themselves.

And XCOR has stated from Day One that they're willing to sell vehicles
to independent operators.

One thing which has not yet been mentioned in this thread is the
concept of the space rotovator.

This is a permanently orbiting rotating cable which a suborbital space
craft can transit to.

As the cable probably something of 1000km long is rotating in the
opposite direction to the orbit it can be arranged so that the Delta V
to reach this is very low.

http://www.liftport.com/forums/showthread.php?t=437

: "steve"
: One thing which has not yet been mentioned in this thread is the
: concept of the space rotovator.

That would be sweet, but is the tech really probable in the near term,
next decade or two? Last I heard, testing of space tethers hadn't
proceeded far at all, and proposals for keeping the main cable in orbit
despite lifting loads, where pretty speculative.


Wayne Throop http://sheol.org/throopw

Jim Kingdon wrote:

Moreover, substantial suborbital operations will create the beginnings of
a supplier base for commercially-priced (as opposed to government-priced)
engines, guidance, materials, safety systems, etc.

It'll be interesting to see how far that effect goes - as most
potential operators seem to be mostly 'rolling their own'

Even at this early stage, there is some evidence that operators are
not just rolling their own. The most obvious example is Virgin:

Operator = Virgin Galactic
Vehicle = Scaled Composites
Engine = SpaceDev

No. The vehicles comes from The SpaceShip Company - owned by...
Virgin (and Scaled) and with an exclusivity clause that prevents the
ships from being sold to anyone but Virgin.

D.
--
Touch-twice life. Eat. Drink. Laugh.

-Resolved: To be more temperate in my postings.
Oct 5th, 2004 JDL

Joe Strout wrote:

Well, for starters, this is almost always the nature of technological
progress. Check out any of Kurzweil's work, for example [1]; he has
plotted quantitative progress over time on a wide variety of
technologies, and finds an exponential curve again and again. The
illusion of linear progress is a result of the fact that, on the very
short timescale at which our attention generally operates, an
exponential curve is approximately linear. But that approximation
quickly breaks down at longer time scales.

To be precise, progress in a technology proceeds in S-curves. A long
slow start which at a certain point curves upwards exponentially, until
it approaches the physical limitations of the scientific principle
being exploited, at which point it asymptotically approaches that
limit. At this point, what generally happens is that a new technology
starts, and the S-curve repeats itself for that technical purpose. You
can see this in transport tech with (for example) railroad trains,
groundcars, and airplanes. What Joe's saying is that we're almost done
with the long slow start phase and orbital spaceflight is about to grow
exponentially. I hope he's correct on this.

Next, let's consider all the things that were being done wrong for the
last 30 years, which are finally starting to change:

- Space was developed as a massively wasteful government program;
without any tangible benefits, such programs are politically
unsustainable, leading to the stagnation we have seen. Now, we are
seeing substantial progress being made on a commercial basis (e.g. Zero
Gravity, Virgin Galactic, SpaceX), and this is far more likely to be
self-sustaining, leading to progress.

Yes. The reason is that private carriers are more likely to push for
efficiency over prestige or perfection.

- Once the cold war rivalry as justification for space development
evaporated, the space community seized on science as its raison d'etre.
This was a mistake; space science is almost entirely pure research, and
there isn't much money in that (in the short term anyway); moreover,
similar amounts of pure research could be done on the ground for far
less money, making every space project a political battle.

Not only that, but it led to a scientific elitist attitude towards
space as some zone of purity which must never be corrupted by human
beings or their dirty little practical purposes. This has produced
absurdities such as space scientists actively _opposing_ the manned
exploration of space, even though such exploration would actually
advance their research purposes as well (by putting scientists
literally "on the ground" of many of the celestial bodies they want to
study). And, of course, the public has been unenthusiastic about
paying for research whose _advocates_ are arguing is purely theoretical
and never to be of any practical value to any non-scientists!

Now space is
being developed for more mundane but far more profitable purposes, like
space tourism. The only politics involved here is in regulation, and
that seems to be going reasonably well so far.

Right. One thing that helps is that there are multiple national
agencies involved in orbital launches: witness what happened when NASA
tried to block tourism on the ISS.

- Flight rate. So far, about 500 humans have ever been in space.
Virgin Galactic plans to fly about 500 passengers per year. Manned
space launches currently happen at a rate of about half a dozen
(launches, not people) per year; Virgin will be flying more than once
per week. And of course, VG will not be the only game in town; Space
Adventures also seems pretty credible to me in their plans for
suborbital tourism. So in a few years, we're looking at a flight rate
orders of magnitude higher than what we have now. Even if this is
suborbital rather than orbital, this will result in a much faster
feedback & revision cycle, and so faster progress.

.... and the technologies required for suborbital and for orbital flight
are essentially the same; the difference is an issue of single versus
multistage rockets.

- Advances in related technologies. Electronics, GPS, avionics, and
other technologies are now available in forms that were science fiction
30 years ago. They're not only dramatically more capable, but
dramatically cheaper, too. These make up a substantial fraction of the
cost of a spacecraft, even if not the weight, and advances is these
should drive the overall cost down too.

Very much so.

Anybody want to add to this list?

Sure.

More national-level players. The first Space Race was America vs.
Russia. We now see America, Russia and China launching manned
missions; Europe, Japan and Israel are close to manned spaceflight
technology. National-level players are important for two reasons (a)
they do the licensing of private space ventures, and (b) as of yet,
they are doing all the orbital launches.

The more players the merrier because if one player (say, America via
NASA) wants to discourage private space ventures, it wil swiftly find
that the other players are only too happy to take the business away
from them. (This is what actually happened over the last 25 years with
NASA and the Russian Space Agency). Also, if one player (say, Russia)
withdraws from a specific goal such as Lunar Exploration, the other
players can keep advancing towards that goal.

The multipolarity of present space exploration and exploitation renders
it robust; makes it less probable that there will be another Retreat
from Space such as we saw in the 1970's.

Sincerely Yours,
Jordan

Wayne Throop wrote:

My problelm with this one is that you can revise and improve suborbital
flight all you want, and you're still no farther along than the X15 was,
in terms of basic capability. Is there some reason to think this will
spill over to orbtial capability?

Well, yes. Suborbital and orbital technology are just different
aspects of the same technology, which is launch technology in general.
If one launches at less than orbital speeds, it's "suborbital"; if one
launches at greater than suborbital speeds, it's "orbital." What's
even better, there are actual commercial applications of suborbital
technology -- one being thrill-flights, but another one being very
rapid intercontinental air travel. Incidentally, this last application
was long seen by science fiction writers, by the 1940's it was a
standard component of their fictional futures.

My problem with this is that there has been lots of money to be made for
less costly launch capability for some time. Slots for comm satellites,
weather satellites, mapping satellites, and on and on. Projects like
Iridium might have been profitable if the costs of keeping the satellites
up and supplying more were less. So it seems to me there's been economic
motive for a long time, and not much has come of it.

A lot has come of it. The _reason_ why there are multiple space
agencies in the commercial launch business today is _because_ of the
satellite launch work. Much that has come of it, though, has been slow
and incremental improvements in the safety and reliability of the
launchers. This is not as dramatic as, say, a breakthrough leading to
an SSTO reusable space ship, but it is _very_ important to the ability
of private companies to get into the business.

It is possible that
governments block progress, such as insisting that the Shuttle program
can and should do everything. But even so, if somebody else could launch
for a lower price, I don't think they'd have problems getting customers
away from the Shuttle.

They have been doing just that, especially after the _Columbia_
disaster.

Note: I'm wearing my skeptical hat here. I *do* see these points,
and agree that that they are positive. I am not merely dismissing
them, or even attempting to "refute" them. I'm just not very optimistic
on how much they will accelerate progress.

They have been doing so visibly in the last few years. You now have
space tourism, with at least one large corporation interested in
getting into the business and multiple smaller entrants in the field.
You also have at least five national space agencies launching orbital
payloads, and at least two interested in constructing manned Moonbases.
We're seeing a Second Moonrace starting right before our eyes.

Sincerely Yours,
Jordan