> how do we transform the shipyard steel hull of a BDB into
> lightweight SPS girders?
aluminium instead, simply by making it ~50% thicker.
http://www.kastenmarine.com/alumVSsteel.htm
There is some aluminium in the 1963 version of the Sea Dragon:
http://neverworld.net/truax/Sea_Dragon_Concept_Volume_1.pdf
"As for the Stage I tanks, the material assumed for study purposes
was 2014-T6 aluminum. ... The transition structure will be primarily
constructed of aluminum reinforced with stiffeners designed also to
take longitudinal loadings. ... The first-stage fuel tank (RF-I)
would be fabricated of 2014 T6 aluminum in a shipyard in the
following manner. ... The welding of 2014 aluminum in 8 in. thick
plates exceeds the present state of the art. A preliminary material
study was performed to determine the theoretical possibilities...."
Also, one might design his BDB hull in the shape of a tubular girder
section. That way, it would not need to be (extensively) reworked
once in orbit.
> Generally, any hull designed to be made of steel can be made of
> aluminium instead, simply by making it ~50% thicker.
> http://www.kastenmarine.com/alumVSsteel.htm
construction costs?
> http://neverworld.net/truax/Sea_Dragon_Concept_Volume_1.pdf
> "The welding of 2014 aluminum in 8 in. thick plates"
And this is why it's only partially useful. It is very difficult to
transform such material into anything remotely useful. The expense, mass,
and cost of the factory needed to do this would very likely make the concept
uncompetative against other supply systems.
It doesn't need to be dismantled and made into something useful - it is already something useful. It is a orbiting volume capable of holding more than one atmosphere of pressure. The space shuttle ET has a bigger interior volume than the ISS and Mir put together, and keeping them in orbit makes heaps of sense, even if only being reused as a propellant depot. Yes there are engineering issues such as the spray-on foam insulation outgassing, circularizing orbit, establishing control, propulsion, navigation, power and so forth, but those are solvable. The Martin Marietta engineers already solved most of those issues with an Aft Cargo Carrier back in the 70s. Ed
> Generally, any hull designed to be made of steel can be made of
> aluminium instead, simply by making it ~50% thicker.
> http://www.kastenma rine.com/ alumVSsteel. htm
Ah. So you'd (partially) solve the problem by dramatically increasing
construction costs?
> http://neverworld. net/truax/ Sea_Dragon_ Concept_Volume_ 1.pdf
> "The welding of 2014 aluminum in 8 in. thick plates"
And this is why it's only partially useful. It is very difficult to
transform such material into anything remotely useful. The expense, mass,
and cost of the factory needed to do this would very likely make the concept
uncompetative against other supply systems.