How is the rocket equation relevant? (was Why Sustainable Power is U

>> The problem with getting anything into space is the
>> rocket equation. For example using the best chemical
>> rockets a 6000 ton liftoff rocket delivers 100 tons
>> to GEO, that's one part in 60.
>
> Then how did the Sea Dragon lift to LEO for $8.90/lb?

It's been a long time since I looked at the Sea Dragon. But I
recently ran though the fuel numbers for Professor Koelle's Neptune.

http://htyp.org/Hundred_dollars_a_kg/Note_1

Assuming penny a kWh power, the energy cost for making LH2 and LOX for
the Neptune was close to $5/kg to GEO and the energy payback was
around 40 days.

But to get 10,000 tons to GEO used up a $1.5 billion rocket (rated for
100 flights) and cost $1.5 billion in operations. So the rocket cost
was $3 billion/10,000,000 kg or $300/kg. It's the high cost of buying
and maintaining aerospace hardware that drives up the cost. As I
recall, the Sea Dragon was to cost what ships do to manufacture.

> http://neverworld.net/truax
> http://neverworld.net/truax/Sea_Dragon_Concept_Volume_1.pdf
> http://neverworld.net/truax/Sea_Dragon_Concept_Volume_3.pdf
>
> If the question is cost, how is the rocket equation relevant?

Because the rocket equation concentrates the cost of the rocket into
the payload.

Sea Dragon design tried to get the cost of the rocket way down. The
other way is to jack the exhaust velocity way up so you get a high
fraction as payload.

Neptune is about 60 to one. Pop up and push might get down to 12 to
one, 25 tons of payload for 300 tons liftoff

Keith Henson