SSTOs

also_larrison wrote: To be generous to Harry Stine, who I met multiple times at
conferences, a lot of the difference is a difference of
interpretation on circumstances and situations. Harry
would look at a situation and immediately claim "XX" was
going on, but when I looked into it, I would find there
were other less exciting, but probably more realistic
situations going on.

I never met the man and I didn't know who he was until I got the book
and I looked him up on the web and found he was dead. Opps!!!
Well, I guess data can lead to different theories. I don't know enough to judge.
Moreover, the hidden assumption in Stine's model seems to
be that he assumes a vehicle is bought from an existing
production line, no (or very little) new infrastructure is
needed, and that there is a large un-met, immediate demand.
These assumptions seem fairly optimistic in the immediate
near term, such as within the next 10 years.
Those assumptions might be true for a second- or third-
generation SSTO, when the markets are known, the operations
refined, and the technology well understood. But for a
nearer term case, a more realistic commercial SSTO case
might assume the initial cost of vehicle will be higher and
there will be some development cost incurred in getting it.
The development cost for the vehicle has to be recovered --
either by the developer selling multiple vehicles to
multiple operators, or by taking back an equity stake in
the operations entity, or through some other party
absorbing the development cost (such as NASA or the USAF).
If you assume some amount of investment cost has to be
recovered, then the effective price to the operational
entity goes up, and the prices have to increase comensurate
to allow the rate of return back to competitive levels.

I always assumed even before I read Stine's book was that the first 2 markets
for reusable spaceships would be satelite launches and fast passenger and cargo
transport around the world. The satelite market already exists and the second
market might be kicked off by flying a ship from New York to Tokyo in under an hour
and then back again 2 days later. I think such a stunt showing that it could be possible
might encourage investors who would then smell the money. A lot depends on how reusable
the ship is, how much it can carry, and how much maintenance it needs.
I would assume the development of SSTO transport would follow the development
of air transport. At first it would be expensive and it would go down as technology
and markets expanded. How fast it might go I have no idea.

NASA has problems, yes. And yes there are people there who
want to protect the programs they've spent years working on
like Space Shuttle. But NASA also has been the primary
source of funding for studying and demonstrating the
technologies for SSTOs for the last 20 years. I wouldn't
say NASA is "wasteful clowns", but that they have not been
able to galvanize public opinion to finance a replacement
to the Shuttle let alone a SSTO demonstrator. There are a
number of reasons for that -- but the DC-X program was a
real sparkplug in breaking through that barrier. From what I read an SSTO is something NASA doesn't want.
I am not talkinging about just Stine's book but various web pages and
interview of various people, etc. It threatens their monopoly.
Certainly not everyone in NASA is like this but if those who make the decisions
are against it then NASA is against it.
I wouldn't say NASA "blocks" the road to space, but that
NASA is one factor that has to be considered, particularly
if you want commercial investment into space activities. A
lot of enthusiasts find it really easy to blame NASA when
they don't want to do the harder work of figuring out the
more detailed things that need to be done to actually pull
it off. And sometimes folks find it easier to blame
someone than change their beliefs. Everything I have read says NASA is part of the problem and not the solution.
I will be the first to change my tune if this is not so but what evidence I have
seen supports my theory. I do agree with you that it is better to try to do something
and figure out how to do it then just wining about NASA. Complaining about a problem
never solves it.
>From another perspective if you look at
the success stories of the space business today (and
commercial space activities product more revenues per year
than NASA's space budget), you'll find that most of them
came out of NASA technology development. Now, they weren't
viable commercial businesses until NASA got out of the field
but many of them started with NASA contracts or NASA-developed
technology. So I'd say its more of mixed bag about NASA
involvement in commercial space activities -- not that they
are just a "block" for space development. You definitely
have to deal with them, but there are some potential pluses
as well as minuses in the equation. I am quite happy about the spin-offs and side effects of NASAs activities
that provide technology and other useful things and the money they generate for the
private sector. I am just annoyed with the fact NASA seems to be a bloated
Beaurocracy now.
Basically, the DC-Y would have to be substantially bigger
than the DC-X, involving different materials, new engines
and quite a different way of going things. It's sort of
like comparing Piper Cessna with a 747. To get into orbit
you need to go around Mach 25, or 25x the speed of sound.
>From a kinetic energy standpoint, you need to put in more
than 25 squared time as much energy into the DC-Y, than the
DC-X (since kinetic energy scales as .5* mass* velocity
squared). That's more than 625 times as much fuel, plus
bigger propellant tanks, plus bigger engines to launch that
big of a vehicle, plus you have to make all the other
changes for orbital flight.
Now, it isn't the math, its that you need the time and
money to go out and actually figure out if you can build
something and put the time and effort into figuring out how
you can build something to do what the math says you want
to do. For example, to make the SSTO work as was being
promised for the Delta Clipper or Harry Stine's
hypothetical SSTO, you need a very efficient (in thrust to
weight) rocket engine that is both reusable and can be
operated at high reliability with little to no maintenance.
That's something no one has ever managed to do.. Can it be
done? I'm pretty sure it can, but its going to take a team
of people some time to figure out exactly how to do it (and
I mean down to doing the full blown detailed design) and
probably quite a bit of testing to make sure you really
know that the engine works. That's cost... I know what you mean, I was playing with the rocket equation recently.
I keep wondering how the reusable ship gets down since to decelerate from orbit
is also a delta-v. To be sure you get air friction to help and gravity will pull down
but you will still need some fuel.
I did think of an idea which I am going to write up in more detail as a way of
solving the design problem. I got the idea when thinking of how Linux was developed.
thousands of hackers(not the people who break into systems but the older meaning of the term as a computer tinkerer) on the internet would design, write and debug the software.
The model depended on the fact that the source code was open and anyone could look at it.
People were invited to modify, debug, fix and improve the code. Since Linux had certain
requirements the best code was chosen to be included but it was and still is under constant development. Why cannot rocket design be done the same way? Certainly
the actual testing of engines and ships would require people with resources to build and
test them but the physics and engineering of the design could be tinkered, debugged,
Keeping the designs open source like with linux allows them to be reviewed
and tested(at least by simulation) by thousands of hobbiests, engineers, physisists,
etc all over the world. A company could access these and find that all the design work
that would cost them millions was done for free by enthusiasts and all they needed to do
was test and build. Maybe a rich enthusiast might have tested some of them already.
It worked so well for Linux. It is just a thought. Hope it catches on though.
I'll agree with this -- but "Halfway to Anywhere" isn't a
technical book. It was a political call to arms, designed
to rile people up and get them enthused about SSTO. It's a
very good book on that basis -- but its not a technical
book. There aren't a lot of good technical books on this
subject since this has been a side light topic without a
lot of major funding for years and year. There are lots of
technical papers around, but they are real technical papers
and rather complex to read since they were never written
for a more general audience. I know Halfway to Anywhere was not a technical book.
I have trouble finding books on Rocketry. I am lucky I held on to
my college physics texts! The math involved never seems that hard either.
It isn't like anyone is being asked to learn linear algebra!
Not that that is a hard subject mind you, I didn't find it that difficult.
We seem to live in a nation of math and science phobics. Bummer.
One of the problems (which came back to bite the McDonnell
Douglas DC-X folks) was that they had promised a bit more
than the company they worked for was willing to commit to.
The company isn't run by true believers, and even if you
are a true believer you have a legal requirement to make
the best decisions for your stockholders. But, the
enthusiasts couldn't understand why the company didn't just
go ahead and build a SSTO after being promised all these
great things the Delta Clipper would do (meanwhile the
company was struggling to stay solvent at one point). At
another point, the enthusiasts tried to re-direct the
company to put billions into SSTO (which didn't make the
company managers fans of DC-X), and at another time tried
to cancel one of the mainstays of McDonnell Douglas's space
business in favor of putting more funds into SSTO. There
was a lot of fuzzy thinking going on about SSTO and not of
lot of folks sitting back trying to rationally think
through what was necessary to pull off an SSTO, let alone
one a commercial investor would put their money into.

The problem I observed with people trying to get other people to
do things, especially if it is risky or visionary, is the need for salesmanship.
The case for a full SSTO delevopment program was not made to McDonnell Douglas
in such a way as to convince them of its value to the company, not even as a long term
goal. I suspect you need more than one company involved anyway.
Even if McDonnell Douglas builds a wonderfully designed SSTO that can carry 50 people
or a nice amount of cargo anywhere in the world or into space and is fully reusable,
cheap to run, etc, someone needs to buy them. You need to get shipping companies,
airlines, satelite launch customers, space tourism developers, etc interested
long before the ships roll out of the factories or there may not be a market
large enough. To do all that requires a salesman with vision and financial savy.
Someone who can get people with money excited about something that is risky
but could pay off really big! He also needs to sell it to the people of the world too
so they will want it and thus creat a market looking for a seller so large that
the risk will seem small. A salesman or a sales team would do the trick.
That any anything that lowers the cost of research such as my opensource rocket design idea.
I fully agree. The DC-X did everything they asked for it
to do, and was a wonderful success in generating enthusiasm
for SSTO development and funding to start developing what
was necessary to do a real SSTO. But how far did it really
push the technology forwards for SSTO? Well, It was the first reusable rocket. It sparked an interest in spaceflight
that died out in the late 80s in me and in several others I knew. I am sure many people
now are interested in sapce flight who gave up when the realized they were never going to go into space when the delta clipper held out the promise of cheap spaceflight again.
Publicity of an idea pushes technology forward by getting people involved in developing
it.
>
Stine's book is not a technical book. To really understand
the technical issues though, you'll have to go dig up some
of the good technical papers put together from the trade
literature -- which means you'll have to dig into Journal
of Spacecraft and Rockets, AIAA journal, AAS, and others.
STAR and RECON are good data bases to start with, but
you'll have to weed out the really detailed stuff from the
higher level systems and conceptual papers. I know they
exist because I've read a bunch of them. I know Stine's book wasn't technical. I checked up on
the SSTO designs he mentioned and his fuel/Mass ratio arguements
using the rocket equation. I keep wondering if there is a way to get
the exaust velocity higher. If you could only get it higher the fuel you would need
would go down.
If you want to talk about this more, drop me a line.

Ok.
Darkstar