Could we get this into space?

[All Seeing Eye]

OK, MagBeam Propulsion it is then.

OMG i've had a brain storm!

We use a propulsion system that can connect and disconnect at the aft of the main craft, that means both the propulsion system itself and the fuel tank. Before the ship is launched towards Mars a seperate aft section is slung towards Mars and enters Mars orbit, because it is slung there by some kind of slingshot device it expels only a small amount of fuel and expels it only when it gets to Mars in order to enter orbit.

When the ship itself gets to Mars it disconnects the depleted aft section and then connects the spare aft section full of fuel for the journey home.

In case something goes wrong we could sling a spare aft section just as a precaution.

 

[scotthm]

Before the ship is launched towards Mars a seperate aft section is slung towards Mars and enters Mars orbit, because it is slung there by some kind of slingshot device it expels only a small amount of fuel and expels it only when it gets to Mars in order to enter orbit.

Now we have to invent a whole new line of rubber band technology.

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[Jadzia]

That's just unrealistic T.

I know you have a dream, but the onboard power issue really is the crux of the problem. Nuclear could work, but it's not gonna be a runabout, it'd be a monster. We're talking of something with more output than sellafield on the back of a ship which has to be at least that big just to carry its generator.

If we find a decent solution to our Earth-bound energy crisis, such as easier form of nuclear fission, or fusion, we could transfer that technology into spacecraft.

But honestly, I don't hold much hope for that happening any time soon.

I doubt we'll ever get these kind of delta-flyer-type space cars, you're dreaming about.

 

[All Seeing Eye]

Before the ship is launched towards Mars a seperate aft section is slung towards Mars and enters Mars orbit, because it is slung there by some kind of slingshot device it expels only a small amount of fuel and expels it only when it gets to Mars in order to enter orbit.

Now we have to invent a whole new line of rubber band technology.

---------------

Something like this but in orbit should suffice.

 

[Jadzia]

I've done a few calculations just now, which admittedly were rushed so I might be wrong.

We have a ship weighing 100 tonnes. Power production is such that the ship experiences negligible loss of mass through one trip to a nearby planet and back.

I think this is a reasonable specification for an interplanetary runabout. Fuel shouldn't be so poor that it is the bulk of the ship's mass, nor should it be so tightly measured that we only have enough for one little journey. It should be consumed at a similar rate to a car: Fuel is maybe 10% of the mass of the vehicle, and that is enough to last you a couple of long distance round trips, and with enough freedom for you to run a couple of errands to the moon on your way home, should you decide to do so.

Suppose we spend approximately 10% of our journey accelerating, 80% cruising, and 10% decelerating, then what power output must our engines have, if the journey to a nearby planet (eg, Mars) takes:

(1) 1 day; (2) 10 days; (3) 1 year


Answers: consider that 1 nuclear power plant produces around 1 GW.

(1) 20000 GW
(2) 20 GW
(3) 0.5 GW



I hope that puts things into perspective for you Tachyon.

 

[Alpha_Geek]

An additional factor- How many G's you pulling to get to Mars in a day or in 10 days?

Signed,

Mr. Pancake

 

[Jadzia]

I had thought of that

(1) 1 day :: around 20 g (fatal)
(2) 10 days :: < 1 g (happy)
(3) 1 year :: negligible (essentially weightlessness)

This reveals that even the 20GW engines are not powerful enough to push against the earth's gravity. It wouldn't get off the launchpad. You'd need maybe 100GW at launch, and gradually reducing this once you are up and away.


The link below tells you more about the energy available in given masses of fuels. Interesting data, and see how hydrogen combustion leads the way for chemical energy:

http://en.wikipedia.org/wiki/Calorific_value#Heating_value

Most hydrocarbons (under oxidation) yield around 45-50 MJ/kg
Hydrogen (under oxidation) yields 140 MJ/kg
Uranium (under fission) yields 2,000,000 MJ/kg

 

[All Seeing Eye]

Jadzia, I appreciate all the calculations you're doing and how much thought and energy you're putting into all this but to be honest stuff like those calculations and fuel consumption etc just boggles my mind. It just looks like gibberish to me.

So what you're saying is that it may be possible for such a craft to get to Mars and back without expelling all it's fuel but it would take maybe a year?

 

[All Seeing Eye]

and is 100 tonnes a correct weight for the type of craft we're talking about?
How much does a space shuttle weigh? because the type of craft we're talking about would be larger than a space shuttle.

EDIT: Oh wait, I think a space shuttle weighs like 72 tonnes so 100 tonnes is probably near enough right.

My bad.

 

[Jadzia]

What I'm saying is that you can build your scrapheap challenge "delta flyer" for us. (Remember we want separate bedrooms )

I estimated the delta flyer size ship at 100 tonnes. I might be wrong.

Find a way of installing a nuclear power plant in the aft section capable of outputting 1 GW (sellafield in a can)

That would be powerful enough to drive us to Mars, but it will take a year to get there.

It would perform like a car: having enough fuel to do several round trips before needing refueling with more plutonium.

The engine output would high enough to run a chemistry lab for converting our waste products into water, oxygen, and sustenance. For an unlimited mission time.

However, this craft would need taking up to orbit on the back of a rocket. It can't take off from ground level because its nuclear engine is not powerful enough.

Also I'm saying that if you made the reactor 20x more powerful, it could get you to Mars and home again in three weeks. And the g-force would be safe and tolerable. But it would still have trouble lifting off from Earth.


However, it would just about be able to land and lift off Mars' or the Moon's surface, because they have much weaker gravity.

 

[All Seeing Eye]

What about this for a propulsion system?

What I'm saying is that you can build your scrapheap challenge "delta flyer" for us. (Remember we want separate bedrooms )

Seperate bedrooms!!! darn it.

 

[Jadzia]

Here. This website tells everything you want to know about the possibility of nuclear space ships:


http://www.projectrho.com/rocket/