Need help building a spaceship propulsion unit.

[jguerin]

I am trying to build a spaceship engine with a specified effect and can use some suggestions.

 

The ship will be based loosely on Newtonian physics with constant acceleration. If the ship flys 10” in one phase, 20” in phase two, 30” in phase three, etc as long as it keeps acceleration with the only upper limit to acceleration will be the fuel it carries. This is pretty standard to build with the cumulative advantage. The troubling part is how to write up the fuel source. The fuel is extremely easy to acquire and readily available cheaply at just about any location a ship can dock at but the ship needs to consume the fuel only when it accelerates or decelerates. For example, the ship with two engines embarks on a voyage with 20 units of fuel. The ship accelerates to a speed of two hexes per turn. Since both engines burned the fuel, however, this means that four units of fuel have been used (one for each inch of flight per engine). The ship later on increases acceleration by 3” burning an additional 6 units of fuel. The ship is now traveling at 5” and has used 10 units of fuel. The ship now has just enough fuel to decelerate at its destination.

 

Any suggestions on how to build the fuel consumption for this type of drive?

[Basil]

Re: Need help building a spaceship propulsion unit.

 

I would suggest taking an idea I've seen on these board (which I think was barely mentioned in Star Hero):

 

Consider "hexes" of Flight to represent acceleration, NOT velocity. Thus, using (say) 10" of Flight is automatically an acceleration of ten hexes per phase per phase (what an ugly-sounding unit that is).

 

Note that this means you "coast" when you're not accelerating, and you don't need Cumulative to go faster. Much simpler.

 

Then, just run the Flight off an END Battery that has a REC dependant on accessing a fuel source. If you're not pumping in fuel, you don't get a Recovery, and you risk running out of fuel.

[AmadanNaBriona]

Re: Need help building a spaceship propulsion unit.

 

I would suggest taking an idea I've seen on these board (which I think was barely mentioned in Star Hero):

 

Consider "hexes" of Flight to represent acceleration, NOT velocity. Thus, using (say) 10" of Flight is automatically an acceleration of ten hexes per phase per phase (what an ugly-sounding unit that is).

 

Note that this means you "coast" when you're not accelerating, and you don't need Cumulative to go faster. Much simpler.

 

Then, just run the Flight off an END Battery that has a REC dependant on accessing a fuel source. If you're not pumping in fuel, you don't get a Recovery, and you risk running out of fuel.

 

*pssst*

Hey Basil.... They've been called END Reserves for at least 2 editions.

You're showing your age

[jguerin]

Re: Need help building a spaceship propulsion unit.

 

Defining inches of flight as acceleration instead of velocity is a good suggestion and easy enough to implement. Should I just use charges for the fuel?

[Chris Goodwin]

Re: Need help building a spaceship propulsion unit.

 

Star Hero does in fact define that as an option for vacuum environments. Also note, 60/SPD inches per Phase is one G of acceleration (also in Star Hero).

 

You can use Fuel Charges if you like. I prefer Basil's idea of an END Reserve with limited REC.

[Basil]

Re: Need help building a spaceship propulsion unit.

 

*pssst*

Hey Basil.... They've been called END Reserves for at least 2 editions.

You're showing your age

 

No, I'm showing the age fo the people I've heard and read (sometimes on these very boards) call it that.

 

That's my story, and I'm sticking to it.

 

[Thia Halmades]

Re: Need help building a spaceship propulsion unit.

 

No, he's right. I started in 5th and I call it a bloody END battery. So nyah. And you KNOW I started only a year and change ago, ANB.

 

Insofar as the mechanics suggested, I agree with my peers, to be quite honest. Delta V movement is defined in game (in either 5ER or TUV or SH, or all of the above). This is also how I plan on handling it for my campaign.

[AmadanNaBriona]

Re: Need help building a spaceship propulsion unit.

 

No, he's right. I started in 5th and I call it a bloody END battery. So nyah. And you KNOW I started only a year and change ago, ANB.

 

Insofar as the mechanics suggested, I agree with my peers, to be quite honest. Delta V movement is defined in game (in either 5ER or TUV or SH, or all of the above). This is also how I plan on handling it for my campaign.

 

Heh.

Sometime I should decribe to you the crazy way End Batteries used to work, and some of the BUH-ROKEN ways that they could be abused.

 

To at least vaguely contribute...

I agreee that the default campaign assumption should cover 0G acceleration as cumulative. The fact that you have to use similar "negative" acceleration to slow down balances it out.

I'm also quite fond of the END reserve "Engine"/Recovery based on fuel model. It works well without adding too much complexity

[Chris Goodwin]

Re: Need help building a spaceship propulsion unit.

 

Heh.

Sometime I should decribe to you the crazy way End Batteries used to work, and some of the BUH-ROKEN ways that they could be abused.

 

Hee hee.

[jguerin]

Re: Need help building a spaceship propulsion unit.

 

The only problem I see with and Endurance Reserve is to factor in multiple engine consumption, ie 2 engines going 2" uses 4 units of fuel, if a vessel had 3 engines going 2" it would use 6 units of fuel..but still only travel 2".

 

The number of engines is a special effect of the size of a ship..all ships will have the same velocity, just that as the ship gets larger, it has to mount more engines to maintain the same velocity.

[Chris Goodwin]

Re: Need help building a spaceship propulsion unit.

 

So you buy Increased Endurance Cost for larger ships. Say, for every three levels of Size above X, all Flight takes one level of Increased Endurance Cost.

[jguerin]

Re: Need help building a spaceship propulsion unit.

 

So you buy Increased Endurance Cost for larger ships. Say' date=' for every three levels of Size above X, all Flight takes one level of Increased Endurance Cost.[/quote']

 

Perfect! Thanks

[jguerin]

Re: Need help building a spaceship propulsion unit.

 

Then' date=' just run the Flight off an END Battery that has a REC dependant on accessing a fuel source. If you're not pumping in fuel, you don't get a Recovery, and you risk running out of fuel.[/quote']

 

Would the Endurance Reserve be written up go like this?

 

 

Fuel Supply: Endurance Reserve (10 END, 10 REC) (11 Active Points); Requires Fuel to REC (-2) Total Cost 3

 

Assuming the refueling is not easy to get, -1/4 if its easy obtained? Or should I do REC at 0 with a lim of needing fuel?

[Roy_The_Ruthles]

Re: Need help building a spaceship propulsion unit.

 

You may want to have it take longer than 1 post phase 12 to refuel, a few min at least.

 

And my gut reaction wants more END in the end reserve, but that's because it's so cheap, not because it fits in your game :-p

[jguerin]

Re: Need help building a spaceship propulsion unit.

 

You may want to have it take longer than 1 post phase 12 to refuel, a few min at least.

 

And my gut reaction wants more END in the end reserve, but that's because it's so cheap, not because it fits in your game :-p

 

I was just picking arbitary numbers what I was focusing on was could I buy the endurance reserve without a specified REC and use the lim of needing to refuel or, if this is against the spirit of rule (which I think it is) buy REC at just 1 or whatever with the lim of needing to refuel.

 

Even with large amounts of END it's going to be cheap because the reserve will only be to power the drives, since its a fuel source for the drive and not the rest of the ship, and will have the power lim of needing to refuel.

[Basil]

Re: Need help building a spaceship propulsion unit.

 

Would the Endurance Reserve be written up go like this?

 

 

Fuel Supply: Endurance Reserve (10 END, 10 REC) (11 Active Points); Requires Fuel to REC (-2) Total Cost 3

 

Assuming the refueling is not easy to get, -1/4 if its easy obtained? Or should I do REC at 0 with a lim of needing fuel?

 

The Limitation should only be applied to the cost of the REC, not the END. And yes, you should buy the REC; putting it at 0 means no Recovery, the "refueling" bit doesn't change that.

[Thia Halmades]

Re: Need help building a spaceship propulsion unit.

 

Hey, you know what i forgot? Engines. Anyway, HERO: Combat Evolved uses the Teleport/Megascale (1" = 1 lightyear) model. Bigger engines have bigger sub-space drives, but the "standard" is a 10 LY jump, however, I'm still trying to find out how far they can go in a single shot.

[Vanguard]

Re: Need help building a spaceship propulsion unit.

 

Something else you could do, if you want to go with the 1 engine uses 2 units of fuel (end) and 2 engines use 4 is to do just that. Figured out how fast you want your ship to move (or how many engines you have on it) and then buy each engine separate so that it's got it's on End cost. Then have them draw from the same End Reserve.

 

Little bit more complicated, book keeping wise, but it's another way to do it if you want.

[Chris Goodwin]

Re: Need help building a spaceship propulsion unit.

 

30" of Flight uses 3 END/Phase.

 

If you want it to cost more END, buy Increased Endurance Cost. The SFX for your Increased Endurance Cost is that it's a more massy ship and therefore requires more energy (i.e. more engines) to get the same amount of velocity (acceleration).

[Wyrm Ouroboros]

Re: Need help building a spaceship propulsion unit.

 

Despite presumptions to the contrary, if you're working primarily with Newtonian physics there is a 'top end' in space -- specifically, the amount of crap your shielding can deal with. While dinking around at sub-cee-fractional speeds you haven't a worry in the world, when you start hitting some serious speeds, well, you need to worry about that stuff.

 

Interplanetary/interstellar hydrogen and miscellaneous microscopic particles may be comparatively rare at 1 atom per cubic centimeter (and for the dust, only 1% of the interstellar medium, which itself is about 5% of the galactic mass), but at .1% of the speed of light you're running through about 150,000 hexes per second (i.e. segment), and thus 1.2 trillion molecules per second. No, this isn't a lot of weight -- 2 x 10^-12 grams -- but you are flying at 0.01c, a measureable fraction thereof, at which point that mass has an appreciable amount of energy.

 

Damned if I know how much energy, but I trust someone here is enough of a mathemetician and physicist to tell us. And to tell us how much shielding you need to 'defend' your ship from just such a constant bombardment ...

[Basil]

Re: Need help building a spaceship propulsion unit.

 

Interplanetary/interstellar hydrogen and miscellaneous microscopic particles may be comparatively rare at 1 atom per cubic centimeter (and for the dust' date=' only 1% of the interstellar medium, which itself is about 5% of the galactic mass), but at .1% of the speed of light you're running through about 150,000 hexes per second (i.e. segment), and thus 1.2 trillion molecules per second.[/quote']

If and only if:

A) a "hex" of volume is 8 cubic meters. I believe it's usually assumed to be 4*sqrt(3) {~6.9282} cubic meters, but I vastly prefer 8 cubic meters as you've done here, and will use that figure throughout this post.

you have a cross-section area of one "hex" of area.

 

No' date=' this isn't a lot of weight -- 2 x 10^-12 grams -- but you [i']are[/i] flying at 0.01c,

You just said .1%, aka 0.001c. If you want to use the higher figure, increase the volume and mass figures by a factor of 10.

 

a measureable fraction thereof, at which point that mass has an appreciable amount of energy.

 

Damned if I know how much energy, but I trust someone here is enough of a mathemetician and physicist to tell us. And to tell us how much shielding you need to 'defend' your ship from just such a constant bombardment ...

At 0.01c, we can still ignore the relativistic effects (increased mass and compacted distance), and use the Newtonian formulae (obviously, this is even more applicable at 0.001c).

 

E=½mv²

E=.5 * 2 x 10^-16 * (.01 * 2.998 x 10^8)^2

E=0.08988 Joules

Since this is a continuous process, this is = 0.08988 Watts. Of course, this is per "hex" of cross-sectional area.

 

BTW, I changed it to 2 x 10^-16, because Joules/Watts are based on kilograms (also to handle the higher velocity). Also, note that at 0.001c, the energy (and power) drop to one one-hundredth as much, because they are drependant on the square of the velocity.

 

In short, unless your craft has a dang big cross-section, you don't have much to worry about.

 

Except, of course, for those dust grains.