Re: starship-design: HOTOL SeaDragon idea.

[KellySt@aol.com]

In a message dated 12/2/2002 1:47:55 PM Eastern Standard Time, ben franchuk <bfranchuk@jetnet.ab.ca> writes:

>KellySt@aol.com wrote:
>> 320 isp with LOx/LH??  Thats hardly better then the numbers for the 
>> LOx/Kerosine engines of the '60's?  Its actually worse then the current gen 
>> of LOx/Kero engines which get up to 350 isp!  Shuttle LOx/LH engines get 
>> about 450isp!
>
>> A 747 has a empty weight about half its max takeoff weight.  Course it has to 
>> takeoff at slower speeds.  I think lift is one of those V^2 things.  Given 
>> the size of this monster, it can handal light seas at speed.  Probably lift 
>> off into its ground effect, then run up into far high speeds for assent.  
>> (lots of open ocean out there.)  So possibly tripling its speed to 450-500ish 
>> mph could get you 9 times the take off weight?  That big Russuan surface 
>> effect ship had numbers like that.
>
>The problem with Rocket design is because things are so sensitive to
>the isp factor a minor change can throw a design right out the window.
>I think a smallish designed craft can be optinum for mass/payload in
>the 800 kg/2400 kg range providing the second stage is unmanned to
>a fixed space platform. Has any work on a third stage using microwave
>or solar powered engine that stays in orbit and captures the second
>stage?
>1st stage -- air breathing/wings manned
>2nd stage -- payload pod /winged reentry
>3rd stage == booster shuttle/space frame
>Ben.


ISP isn't a critical cost factor, though you need to avoid designs with ISP to do it.

Its worth noting that airbreathing systems have ISP's in the thousands, so they make up for a lot of upper stage issues.

As to solar or microwave upper stages, only for orbit to orbit transfers.  They simply don't mave the raw power needed for burning into Earth orbit.

Their was some studies of a mid orbit intercept by a nuclear powered tug.  In theory you could do a factor of ten increase  cargo to orbit with a rocket based SSTO, overloaded into a suborbital capacity to intercept the boster tug.  NOt real sure I'ld recomend the idea though.  might as well just add the nuke to the upper stage or cary more fuel, and deal with a simpler system.

Kelly