In the Early 1960's, Aerojet designed a BDB (sea dragon) capable of putting
550 tonnes into LEO
http://www.friends-partners.org/mwade/lvs/searagon.htm
design a BDB today, how would we design for minimum cost? I suppose that we
could use fibre-glass for much of the upper stage design. With a 550 tonne
to LEO booster, we could assemble something like the ISS on the ground and
fire it into orbit in one piece. This would surely be much cheaper than
carting 30 different pieces up on the ultra-expensive shuttle and trying to
assemble them in a vacuum.
The BDB that I had in mind would have a lift capacity closer to 1000
tonnes to LEO. Something like this, would be capable of putting 200 tonnes
of men and materials on the lunar surface or alternatively, 500 tonnes in
HEO or 450 tonnes on a NEA.
Tony
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income streams, from the comfort of your own home.
>
> In the Early 1960's, Aerojet designed a BDB (sea dragon) capable of
putting
> 550 tonnes into LEO
> http://www.friends-partners.org/mwade/lvs/searagon.htm
>
> I have been looking at various designs and BDB concepts. If we
were to
> design a BDB today, how would we design for minimum cost? I suppose
that we
Minimum cost BDB is a STS derived HLLV. Scrap the orbiter, replace
with cargo container and expendable engines. This would require the
least ammount of R&D and testing compaired to building a new launch
system from the ground up (no pun intended).
king_rodent (putting the eek in geek)
> >
> > In the Early 1960's, Aerojet designed a BDB (sea dragon) capable
of
> putting
> > 550 tonnes into LEO
> > http://www.friends-partners.org/mwade/lvs/searagon.htm
> >
> > I have been looking at various designs and BDB concepts. If we
> were to
> > design a BDB today, how would we design for minimum cost? I
suppose
> that we
>
> Minimum cost BDB is a STS derived HLLV. Scrap the orbiter,
replace
> with cargo container and expendable engines. This would require the
> least ammount of R&D and testing compaired to building a new launch
> system from the ground up (no pun intended).
system = brand new VAB, transport, launch gantry, roads, pipes, fuel
depo's, launch control centers, data lines, power lines, ect. STS
HLLV would require very little in augmentation to the assembly
building and launch gantry.
king_rodent (putting the eek in geek)
>
> In the Early 1960's, Aerojet designed a BDB (sea dragon) capable of putting
> 550 tonnes into LEO
> http://www.friends-partners.org/mwade/lvs/searagon.htm
>
> I have been looking at various designs and BDB concepts. If we were to
> design a BDB today, how would we design for minimum cost? I suppose that we
> could use fibre-glass for much of the upper stage design. With a 550 tonne
> to LEO booster, we could assemble something like the ISS on the ground and
> fire it into orbit in one piece. This would surely be much cheaper than
> carting 30 different pieces up on the ultra-expensive shuttle and trying to
> assemble them in a vacuum.
> The BDB that I had in mind would have a lift capacity closer to 1000
> tonnes to LEO. Something like this, would be capable of putting 200 tonnes
> of men and materials on the lunar surface or alternatively, 500 tonnes in
> HEO or 450 tonnes on a NEA.
these, or many. If many, developing something new from scratch (or based
on reasonably good existing designs) is definitely the way to go - the
operational cost of using a design based on the shuttle, and using its
facilities, is going to be ridiculously high.
One problem with BDB's or any large rocket is transport and assembly
from the manufacturing facility to the launch pad. Transport over land
for any significant distance is vastly more expensive for objects larger
than a typical shipping container. Transport over water makes things
easier, and if you launch from the water as SeaLaunch does, and as
SeaDragon was supposed to, and manufacture at some coastal facility,
you'll be cutting transport costs quite a bit.
Non-cryogenic fuels simplify fuel transport, transfer, and storage, so
they are worth looking at even with the lower specific impulse. Since
BDB's are generally expendable, you'll save costs using cheaper
materials; fiberglass, or steel say. Probably more important is ease of
manufacture: what is the lowest precision in parts that's acceptable?
Having lots of comfortable margins is a good way to reduce operational
costs - you don't have to so precisely monitor everything if you have
20% extra fuel as if you have only 5% extra for the mission; but of
course there's a balance there with the loss of cargo capacity. Other
redundant systems similarly can reduce operational costs by limiting the
things you have to worry about, but also reduce cargo capacity and
increase the sunk costs in expendable systems.
I'd be interested to know who is actively working on any such thing? The
real problem seems to be the lack of a market, the usual chicken and egg
problem.
Arthur Smith (apsmith@...
>>>>Non-cryogenic fuels simplify fuel transport, transfer, and storage, so
they are worth looking at even with the lower specific impulse. Since
BDB's are generally expendable, you'll save costs using cheaper
materials; fiberglass, or steel say. Probably more important is ease of
manufacture: what is the lowest precision in parts that's acceptable?>>>>
soft cryogen (b.p. -182.962C).
Another alternative fuel for a BDB would be liquified-natural-gas/LOX.
Maybe the best solution for a BDB concept, would be a large, re-usable,
Steel lower stage, fuelled with ordinary diesel and LOX. The stage would be
fitted with a single, very large pressure fed engine. The engine would be
inherently simple and robust. The combustion chamber would be heavily lined
with refractory materials, so that no active cooling is required during the
relatively short first stage boosting. The lower stage will not require a
heatshield and would be robust enough to survive impact with the ocean.
After successful firing and 1st stage separation, a parachute would slow
the descent of the first stage so that it would splash down several hundred
Km downrange. The empty fuel tanks would provide enough buoyancy for the
stage to float. The stage would then be towed back to port and refitted
with another upper stage. Turn around times could be kept short.
Lower stages are so large and inherently simple, they are probably best
manufactured in ship yards. Ordinary steel is therefor the best material.
The large, pressure-fed engine, might only have a few hundred parts.
The best material for upper stages is probably fibre-glass. Fibre
glass/epoxy is substantially more expensive than steel, but not
unreasonably so. Using fibreglass, dry weight percentage could be as low as
7% engine included. The advantages to be gained through the use of fibre
glass are lower structural mass fractions, the elimination of special
bending and shaping techniques and special machinery. This is why so many
people use fibre glass as the construction material for boats. If we plan
to mass-produce the upper stages, it may be the material of choice. Upper
stages could be moulded from fibre-glass and mass produced in facilities
like giant car factories. If we were to plan for upwards of 100 launches
per year (one every few days), a mass production facility seems
appropriate.
Tony
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income streams, from the comfort of your own home.
> Lower stages are so large and inherently simple, they are probably best
> manufactured in ship yards. Ordinary steel is therefor the best material.
> The large, pressure-fed engine, might only have a few hundred parts.
yet? They always seem to be anxious to find work, and are pretty good at
lobbying through, for example, the DoD to get more nuclear subs or
whatever built...
Arthur Smith (apsmith@...
>>>>>Non-cryogenic fuels simplify fuel transport, transfer, and storage, so
>>>>>
> Maybe the best solution for a BDB concept, would be a large, re-usable,
> Steel lower stage, fuelled with ordinary diesel and LOX. The stage would be
> fitted with a single, very large pressure fed engine. The engine would be
> inherently simple and robust.
engine gets the more chance there is of 'combustion instability'.
This phenomena has killed one or two Russian programs outright, and
set back some others. Note the Russians are not noted for their
cluelessness in space launch vehicles.
Basically the combustion chamber resonates and sets up some kind of
oscillation with the fuel feeds. The engine frequently fails at that
point. Annoyingly, right before they fail, they apparently can have
greatly improved performance(!) ;-(
The smaller the engine is, the less chance there is of meeting it,
but quite small engines can meet it also; although much more rarely
as they oscillate at higher frequencies which tend to damp out.
Another annoying feature of these instabilities is that they
don't alway's occur and are difficult to test out.
This is one of the reasons that clustered engines are used.
Another advantage of clustered engines is that you need more of them,
but they are all identical, so they can come out cheaper due to buying
them in greater volumes.
Reliability is usually improved with clustered liquids, upto a
point; they rarely fail catastrophically, unlike solids.
> After successful firing and 1st stage separation, a parachute would slow
> the descent of the first stage so that it would splash down several hundred
> Km downrange. The empty fuel tanks would provide enough buoyancy for the
> stage to float. The stage would then be towed back to port and refitted
> with another upper stage. Turn around times could be kept short.
That's not really the BDB idea. The BDB idea is you ditch it in the sea
and buy another one; going for more volume and lowering the cost that
way.
If and when you have enough market to cost reduce the BDB you should be
able to borrow the money as you have a market. One idea is that
reusability is, to a fair extent, antagonistic to reducing launch cost
as it pushes up the costs of the launch vehicle, and probably reduces
performance due to having to make it stronger. A lot of the costs of
a launch vehicle go into the launch facilities and R&D costs;
reusability raises these costs some too.
> Tony
civilization?"
On combustion instability... Beale Aerospace claimed that using hydrogen peroxide as an oxidizer basically eliminated the combustion instability problem. Before they went out of business, they had hot-fired an 800,000 pound thrust 2nd stage engine,and planned to build a 3-million pound thrust first stage engine. Their theory was to use singular rather than clustered engines to reduce complexity, and H2O2 allowed them to do that,apparently.
Ian Woollard
Ian Woollard
>>>>>Non-cryogenic fuels simplify fuel transport, transfer, and storage, so
>>>>>
> Maybe the best solution for a BDB concept, would be a large, re-usable,
> Steel lower stage, fuelled with ordinary diesel and LOX. The stage would be
> fitted with a single, very large pressure fed engine. The engine would be
> inherently simple and robust.
There are problems with scaling up engines in fact. The larger the
engine gets the more chance there is of 'combustion instability'.
This phenomena has killed one or two Russian programs outright, and
set back some others. Note the Russians are not noted for their
cluelessness in space launch vehicles.
Basically the combustion chamber resonates and sets up some kind of
oscillation with the fuel feeds. The engine frequently fails at that
point. Annoyingly, right before they fail, they apparently can have
greatly improved performance(!) ;-(
The smaller the engine is, the less chance there is of meeting it,
but quite small engines can meet it also; although much more rarely
as they oscillate at higher frequencies which tend to damp out.
Another annoying feature of these instabilities is that they
don't alway's occur and are difficult to test out.
This is one of the reasons that clustered engines are used.
Another advantage of clustered engines is that you need more of them,
but they are all identical, so they can come out cheaper due to buying
them in greater volumes.
Reliability is usually improved with clustered liquids, upto a
point; they rarely fail catastrophically, unlike solids.
> After successful firing and 1st stage separation, a parachute would slow
> the descent of the first stage so that it would splash down several hundred
> Km downrange. The empty fuel tanks would provide enough buoyancy for the
> stage to float. The stage would then be towed back to port and refitted
> with another upper stage. Turn around times could be kept short.
That's not really the BDB idea. The BDB idea is you ditch it in the sea
and buy another one; going for more volume and lowering the cost that
way.
If and when you have enough market to cost reduce the BDB you should be
able to borrow the money as you have a market. One idea is that
reusability is, to a fair extent, antagonistic to reducing launch cost
as it pushes up the costs of the launch vehicle, and probably reduces
performance due to having to make it stronger. A lot of the costs of
a launch vehicle go into the launch facilities and R&D costs;
reusability raises these costs some too.
> Tony
civilization?"
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
There are problems with scaling up engines in fact. The larger the
engine gets the more chance there is of 'combustion instability'.
This phenomena has killed one or two Russian programs outright, and
set back some others. Note the Russians are not noted for their
cluelessness in space launch vehicles.
oscillation with the fuel feeds. The engine frequently fails at that
point. Annoyingly, right before they fail, they apparently can have
greatly improved performance(!) ;-(
The smaller the engine is, the less chance there is of meeting it,
but quite small engines can meet it also; although much more rarely
as they oscillate at higher frequencies which tend to damp out.
Another annoying feature of these instabilities is that they
don't alway's occur and are difficult to test out.
This is one of the reasons that clustered engines are used.
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
This is the legendary POGO phenomena. It may be possible to avoid these
problems with advanced computer modelling techniques. This is something
that those industrious Russians just did not have. During the early 60's,
when most of the development was being done, the US didn't have them
either.
Would it be possible to introduce damping of some kind? Maybe some kind of
spring damping system? Many previous BDB studies found that combustion
instabilities were reduced by keeping the feed pressures several atm higher
than the combustion chamber pressures.
Anyway, I'm no rocket scientist. If we manufacture clustered engines by
the thousand, then we might still retain the cost advantage. The amount of
R&D that would need to be pumped into a costly new engine development
program, means that it is probably best if we steer clear of engines that
might develop POGO problems.
On the other hand, some computer models may allow us to anticipate POGO
problems and therefor, allow us to design much larger engines.
Tony
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income streams, from the comfort of your own home.
>>>>On combustion instability... Beale Aerospace claimed that using
hydrogen peroxide as an oxidiser basically eliminated the combustion
instability problem. Before they went out of business, they had hot-fired
an 800,000 pound thrust 2nd stage engine, and planned to build a 3-million
pound thrust first stage engine. Their theory was to use singular rather
than clustered engines to reduce complexity, and H2O2 allowed them to do
that, apparently
the causes of combustion instability? Is this something that we can iron
out of designs with dampening devices and computer modelling?
The Sea Dragon BDB, designed in the early 60's anticipated the use of a
single, huge pressure-fed first stage engine, producing 36 million Kgf of
thrust. Since the design was never built and tested, are we to assume that
the designers of the early 1960's were ignorant of POGO effects?
http://www.friends-partners.org/mwade/lvs/searagon.htm
Tony
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income streams, from the comfort of your own home.
> I'm certainly no rocket scientist. Can anyone give me a basic outline of
> the causes of combustion instability? Is this something that we can iron
> out of designs with dampening devices and computer modelling?
>
Causes: vibrations in the feed line, resonances in the combustion chamber
working as an organ pipe,... There are two remedies: Put a Helmoltz resonator
to dampen vibrations, or use a pintle injector to get a better fuel mixing.
> single, huge pressure-fed first stage engine, producing 36 million Kgf of
> thrust. Since the design was never built and tested, are we to assume that
> the designers of the early 1960's were ignorant of POGO effects?
> http://www.friends-partners.org/mwade/lvs/searagon.htm
The Sea Dragon problems are not technical, they are monetary, Where do you
find the billions to build the first unit?
The only workable alternative is a OTRAG-like design with up to 600 smaller
rockets. Each could have the theoretical possibility to launch may be 2000 kg
in LEO and would have a mass in the 60 - 80 t at take-off. A 120 thrust motor
would do the job on each elementary rocket. Using the V2/A4 injector
clustering technique, such a motor could be derived from a 1/20th scale
system or 6 - 7 t thrust motor, something in the range of amateur desing. I
am working on such a concept for some time now. The first version of that
motor would be itself a 20 cluster, each element with a thrust in the 500
lbf domain. This first step has been ground tested.
Would you be interested in that project? If yes, I can even tell you how to
make money with it right now (no risk, no money going out of your pocket!)
Yvan Bozzonetti.
>> There are problems with scaling up engines in fact. The larger the
>> engine gets the more chance there is of 'combustion instability'.
>> This phenomena has killed one or two Russian programs outright, and
>> set back some others. Note the Russians are not noted for their
>> cluelessness in space launch vehicles.
> problems with advanced computer modelling techniques. This is something
> that those industrious Russians just did not have. During the early 60's,
> when most of the development was being done, the US didn't have them
> either.
Actually pogo is a somewhat easier issue. Pogo is longitudinal
oscillation of the vehicle. It's caused by interactions between the
acceleration of the vehicle and the hydrostatic pressure of the fuel;
and is fairly well understood, and may well be removable
with computer control.
Combustion stability is usually at a much higher frequency, and need
not be longitudinal. It's mainly a mixing thing within the combustion
chamber; and is far more complex.
> Would it be possible to introduce damping of some kind? Maybe some kind of
> spring damping system? Many previous BDB studies found that combustion
> instabilities were reduced by keeping the feed pressures several atm higher
> than the combustion chamber pressures.
Yes. Combustion instability is to do with mixing patterns that varies in
an oscillating way. Combustion instabilities are improved by higher
pressure, and preburners (i.e. using gases rather than liquids)
helps very greatly.
> Anyway, I'm no rocket scientist. If we manufacture clustered engines by
> the thousand, then we might still retain the cost advantage. The amount of
> R&D that would need to be pumped into a costly new engine development
> program, means that it is probably best if we steer clear of engines that
> might develop POGO problems.
>
> On the other hand, some computer models may allow us to anticipate POGO
> problems and therefor, allow us to design much larger engines.
>
> Tony
civilization?"