On Mon, Dec 18, 2017 at 3:50 AM, Rob O'Connor <xxxxxx@ozemail.com.au> wrote:
Richard Aiken wrote:
> So . . . when I give my Fireflyesque multi-function reaction engines
> enough on-board fuel endurance to handle 4 round trips to jump point
> and back from a typical planet for ~5% of ship volume, I'm in the
> right ballpark, physics-wise?

5% volume implies (initial mass/final mass) gets close to one. If the fuel is liquid hydrogen, the mass is about 0.4%. So ln(1/0.996) is ~0.004.... The required exhaust velocity exceeds the speed of light.
 

The fuel is liquid water, which IIRC actually works out to be a more efficient reaction mass (given the relatively uncomplicated storage requirements for water versus liquid hydrogen).

 
You're going to need lots more fuel.
 

Okay. 

 
I decided to push things to the limit with my previous post. What would it take to get the performance level required?

Direct conversion of most of the fuel's mass-energy to kinetic energy.
 

Would running the water through a fusion reactor core accomplish that? If not, would adding an antimatter afterburner (spraying antiprotons into a secondary exhaust chamber) help?


Exhaust (waste energy) is a plume of neutrinos to avoid too many unpleasant interactions with nearby matter.
 

Not sure what the exhaust from my Fireflyesque rockets would consist of materially, but I have serious doubts it would be harmless. I have visions of something like the "hard burn" effect upon that Reaver ship, from the pilot episode. Yet that exhaust only gets really that bad - normally - after the ship has climbed to vacuum, so it's probably not going to nuke anything too important (at least not if the PCs stick to the departure vector assigned to them by traffic control, such that they don't torch any satellites or passing traffic).

  

180G-hours thrust? 0.4% of the volume of the hull is fuel. 3 parts per 10,000 mass units is fuel.
 

So . . . my math makes 5% some 125 times the above amount. Is that close enough to "lots more fuel"?

-- 
Richard Aiken

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