Re: APR Extra: Moderately gigantic drawing of Sea Dragon

From: Pat Flannery (flanner_at_daktel.com)
Date: 03/29/05 

Date: Tue, 29 Mar 2005 03:54:28 -0600

Scott Lowther wrote:

>
> Keep in mind that this is an alternate historey discussion, not a
> "let's do it now" discussion. That being the case, if Orion was a
> going concern in the early sixties, satellite makers would know what
> was coming, and would beef up satellite shielding accoridingly. Since
> this alternate history woudl require vastly more space lift capability
> than the real world, perhaps on the order of a Sea Dragon a day or
> more, space launch woudl be dirt cheap... and thus so would satellites.

You've still got all the infrastructure to support that sort of
spacelift capability; the more Sea Dragons you build, the more the R&D
is divided up between the vehicles, so that cost drops...but the
vehicles themselves still cost money for the material to build them, and
the man hours that go into their assembly, and that will drop as
efficiency of large scale production cuts cost, but it never will be
dirt cheap- the Russians have built literally thousands of R-7 Semyorkas
in various variants, but they still cost a fair amount apiece. And the
satellite itself can be a significant part of the overall price of
launch; you can build large numbers of low-tech heavy and cheap
satellites if the launch price drops significantly, but you end up with
a really severe space debris problem, as well as how many you have to
put on one Sea Dragon launcher to make a launch worthwhile...that's the
problem with the thing- it's very economical- provided that you can use
its total payload capacity on every launch, otherwise the price starts
going up.

>
>> The only real way to make full use of Orion's exceptional ISP is to
>> surface launch it,
>
>
> Incorrect. Launch from ground to orbit requires nothing fancy,

It was going to take 2-3 Saturn V launches to put a 33 ft. diameter
Orion's components into orbit and get it all ready to go... and that's
into LEO. The full size Orions that gain the full efficiency of the
motor concept are probably take more than a Sea Dragon could carry (550
metric tonnes) In fact, the original surface launched Orion design
weighed in at 10,000 tonnes.

> and in fact suffers when launch vehicles are desired to be at the
> bleeding edge. A Sea Dragon, obviously, would do it. Orion provides
> *no* benefit here. The point is not to get the best mass fraction from
> Earth to orbit, but to get the lowest cost per pound from Earth to
> orbit. But Orion can send a shitload of stuff from Earth orbit to
> Jupiter... Sea Dragon can't.

There are two things about this rosy scenario that make me think that
implementing it might be a tad harder to accomplish than it at first seems:

1.) The Sea Dragon's designer is the man who built the rocket to shoot
Evel Kneival across the Snake River Canyon... it got around halfway across.
Then he got hold of some surplus Atlas vernier rockets and designed a
rocket to shoot a guy named "The Human Fly" IIRC up to the edge of
space, Prof. Fate cape and all.
This never got built.
 
2.) The Orion's big champion is the guy who suggested building a shell
around the Sun with a diameter of one Earth orbit, even though there
isn't enough raw material in the entire solar system to make such a
shell structurally sound. He also overlooked the fact that the Sun would
be effectively weightless inside this sphere, and could drift all over
inside of it...so that it would require some means to keep it centered,
or bad things will occur when it decides to leave one day and melts its
way through the sphere's surface.

This whole concept needs one thing added... a means of getting the
colonists around on the Martian surface, given how rocky it is...I'm
thinking modified Moller Skycars driven by small cold fusion reactors
might be just the ticket to solve that problem. ;-)

>
>>
>> You can save trip times to Mars with higher velocity between the two
>> planets (I don't know if the Moon is even worth it in regards to
>> higher velocity; it would be a "hurry up and stop" situation at Lunar
>> distances), but except for crew and passenger movement does it really
>> matter if you get your colonization cargo from point "A" to point "B"
>> in a week, or via a Hohman transfer orbit? That extra speed you used
>> to get there has to be damped out at the arrival at the destination,
>> and that's wasteful.
>>
> Remeber, we're talking about military. These are the guys who
> regualrly bust Mach 1 getting from here to there. Civilians do not do
> that.

It doesn't work very well at distances as short as the Earth/Moon run; a
couple of decades ago (boy, but I'm getting old) I came up with the
ultimate space passenger/cargo ship- it had a drive that generated a 1G
thrust for as long as you wanted it... travel consisted of accelerating
toward you destination at one G, turning around at the halfway point,
and decelerating for the rest of the way there- no weightlessness, no
bone mass loss... you saved time on the Earth/Moon run, but it really
paid off in regards to Mars and the outer planets.
The travel times to Jupiter and beyond were spectacular.
What was the propulsion system to be? Okay, that's a small detail, but
I'm sure that with a little work..... ;-)

Pat