> 2. Has anyone done the calculations to see how much fuel it will 
> take to run
> that thing up into orbit? And could it, or multiple its, lift that 
> much
> fuel?

You can be absolutely certain that they have done extensive 
calculations on what it can achieve BEFORE they ever built it.
I also wondered and have already asked John what altitude it would 
achieve with and without an aeroshell.

Achieving orbit is a factor of (as well as a zillion other lesser 
things) Propellant energy (Isp), drag and mass ratio.
This machine by itself falls far far short of being able to achieve 
orbit in all those areas - it's intended as prototype of part of a 
larger system which will in due course reach orbit. Isp is probably 
around 250. Shuttle achieves 400+. More like 300 would help greatly. 
Drag of this unit, quite apart from the lack of an aeroshell, would be 
badly affected by its large area to length ratio. Drag is far far more 
significant for small rockets due to the square-cube law (area to 
volume ratio goes down as size goes up so, to a first approximation, 
drag effect decreases with size). Mass ratio (Mass_full /  Mass_empty) 
is an utterly crucial factor for orbital systems and for this unit 
would be good but modest. State of the art achieves better than 20:1 
(better than a coke can in some cases) whereas this unit probably has 
an Mr in the 2 to 5 range. This is not to be sneezed at - it's 
amazingly hard to get vastly above this.

The altitude results would depend on all sorts of parameters which are 
either adjustable and/or unknown to me but a rough check with 
guesstimated parameters suggests that "in atmosphere" it would 
probably achieve something in the 20,000 to 30,000 foot range with a 
rudimentary aeroshell, and without atmospheric drag it would be 50 to 
100 miles. Drag matters a lot for something this small.

Note that this is a long long long way away from being orbit capable 
as the overwhelming requirement for orbit is a sideways component of 
about 22,000 mph and at maximum altitude this unit alone would have 
minimal sideways component.

It is in fact intended as the prototype of a modular multi stage 
system.

- Stage three is 2 tanks rather than 4 in that unit, standing on top 
of each other.
- Stage two is 4 of those units.
- Stage one is 16 units.

(Maybe the units are all only 2 tanks stacked vertically - I'd have to 
go and look at the Spacex 2007 video again. Well worth seeing.
All 60 MB of it available here


            http://media.armadilloaerospace.com/misc/sas07_high.mpg

(My existing copy is 63.5 MB so they may have altered it slightly).



"Rocket Science" at a basic level is not that hard. Rocket practice 
can be as hard as you want it to be.

> James. (so not a rocket scientist)




            Russell
            [[Almost vaguely sort of an amateur rocket scientist.]]








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