Alien War: Chemical Rockets ?!?

[DrTemp]

I bought Terran Empire and was amazed. I bought Alien Wars and, well, at least I liked it (though i like Terran Empire a lot more), and both are worth their money.

 

But there is one detail I don't quite understand: The United Earth Ships in Alien Wars use chemical rockets for sublight propulsion.

 

So we have a Centauri class battleship, 100 000 tons, that accelerates at 0.5 g, uses chemical rockets to do that, and has fuel for one month aboard. This computes down to... uhm. 250 million tons of reaction mass. Is that correct?

 

I'd say that is a conceptional error- not a big one, easy to correct (if they were very high efficiency fusion rockets with a specific impulse of 1 million seconds, the reaction mass could go down to as low as 125 000 tons or so), but nontheless it should be mentioned.

 

Or am I overlooking something?

[Outsider]

I dont have the product, so I know this isnt the right explaination, but...

 

 

Maybe the 0.5 acceleration is its maximum combat accel, while the 1 month's worth of fuel is at its much lower "cruising" rate?

[DrTemp]

Originally posted by Outsider

 

[...]

 

Maybe the 0.5 acceleration is its maximum combat accel, while the 1 month's worth of fuel is at its much lower "cruising" rate? [/b]

 

Well, I may have misunderstood the data given, but even then, several dozen million tons of reaction mass for a 100.000 ton-Ship (which thus is about as heavy as a modern-day US Navy Nimiitz class aircraft carrier) is too much anyway.

 

I am pretty sure that the "chemical rockets" should be changed to fusion rockets, which use hydrogen as reaction mass. The latter is just as easy to obtain (or even easier) as Hydrogen-Oxygen fuel for chemical rockets, and the ships in question do already have a fusion reactor aboard.

 

BTW, does anyone know why UV lists fusion rockets and antimatter rockets as "rubber science"? That does not make much sense, since the scientific base for both is as hard as that for a gauss rifle or a fusion reactor.

[CorpCommander]

Originally posted by DrTemp

BTW, does anyone know why UV lists fusion rockets and antimatter rockets as "rubber science"? That does not make much sense, since the scientific base for both is as hard as that for a gauss rifle or a fusion reactor.

 

I can't speak for the author but in the case of anti-matter the problem is where do we collect it from? I've read one essay on a collection system that required a pipeline looped around the Moon. Such large scale engineering is a nice concept but not very practical in terms on actual construction or for political reasons. Still, its less rubbery than Zero-Point energy. At least with Anti-Matter you don't have to make any of the science up.

 

Fusion rockets don't sound very rubbery to me. In fact Stanislaw Ulam saw fusion powered flight as being a realistic goal for the mid-twentieth century: Ulam's Hydrogen Saucer

[DrTemp]

Originally posted by CorpCommander

I can't speak for the author but in the case of anti-matter the problem is where do we collect it from? I've read one essay on a collection system that required a pipeline looped around the Moon. Such large scale engineering is a nice concept but not very practical in terms on actual construction or for political reasons. [/url]

 

Well, a thousands-of-stars-spanning empire should be able to construct large sites that use solar power (or fusion power) to produce antimatter. Should even be economical, given the enormous perfomance increase throuhg antimatter rockets.

[Syberdwarf2]

I could be wrong but I seem to remember seeing documentaries on fusion reactors (Tokamaks?). IIRC, the problem with fusion power not it's creation, it's with its sustainability.

 

Basically, sustainable, safe energy efficient fusion reactions are not currently a reality, but certainly are attainable (in theory) as technology improves.

[CorpCommander]

good point

 

Originally posted by DrTemp

Well, a thousands-of-stars-spanning empire should be able to construct large sites that use solar power (or fusion power) to produce antimatter. Should even be economical, given the enormous perfomance increase throuhg antimatter rockets.

 

which came first? The Anti-matter collection facility or the thousands-of-stars spanning empire? lol.

 

You have a good point though. By the time of the Alien Wars it should be very easy to create such a beast.

[Cybrarian]

Re: Alien War: Chemical Rockets ?!?

 

Originally posted by DrTemp

But there is one detail I don't quite understand: The United Earth Ships in Alien Wars use chemical rockets for sublight propulsion.

 

Just acquired AW this afternoon. Seems to me that the first reference to chemical rockets in the Starships section is a typo/omission/oversight. The paragraph immediately below it specifically says that, "Humans commonly used chemical and fusion rockets for STL movement of starships." My emphasis. The accompanying table lists Fusion Rockets as being developed in 2253, easily in time to be in general use by the 24th century. Just say they're using fusion and roll from there.

 

I wish this had been available two years ago when I started my SF campaign (Star Wars d20 mixed with Traveller 2300.) I'm more and more tempted to actually pull the trigger on converting to Hero.

[DrTemp]

Re: Re: Alien War: Chemical Rockets ?!?

 

Originally posted by Cybrarian

Just acquired AW this afternoon. Seems to me that the first reference to chemical rockets in the Starships section is a typo/omission/oversight. The paragraph immediately below it specifically says that, "Humans commonly used chemical and fusion rockets for STL movement of starships." My emphasis. The accompanying table lists Fusion Rockets as being developed in 2253, easily in time to be in general use by the 24th century. Just say they're using fusion and roll from there.

 

Well, I assume the first working prototypes of a fusion rocket were developed much earlier in the Hero universe. Terran Empire lists even later years for chemical and fusion rockets, so I assume these are simply the introduction dates fo those specific designs of rockets.

 

Of course, fusion rockets are the obvious answer. It's just a pitty they did this one mistake in an otherwise very good work. Drops the overall rating of the book to just "good". 8)

[Cybrarian]

Re: Re: Re: Alien War: Chemical Rockets ?!?

 

Originally posted by DrTemp

Well, I assume the first working prototypes of a fusion rocket were developed much earlier in the Hero universe. Terran Empire lists even later years for chemical and fusion rockets, so I assume these are simply the introduction dates fo those specific designs of rockets.

 

You're right, the dates have to be for the specific designs. By the 24th C, chemical rockets have been around for millennia, centuries if we're talking liquid fuel and/or those actually used in space. An introduction date of 2253 with UTES 7 has to represent a new spin on an old idea.

 

It might still make sense to use chem rockets for attitude adjustment, etc. During docking maneuvers you wouldn't normally want to spray other ships with fusion thrust.

[Metaphysician]

Re: Alien War: Chemical Rockets ?!?

 

Yep, thats the impression I got: fusion rockets.

 

Another thing I noted: given the movement figures, its pretty clear Alien Wars space combat is based on using those movement rates as acceleration figures. Which makes sense, given the 30"/60" is pretty much exactly the human acceleration limit.

 

Makes for some interesting consequences on how battles are fought tactically, given a detailed look. . .

[travellerne]

Re: Alien War: Chemical Rockets ?!?

 

I'd say that is a conceptional error- not a big one, easy to correct (if they were very high efficiency fusion rockets with a specific impulse of 1 million seconds, the reaction mass could go down to as low as 125 000 tons or so), but nontheless it should be mentioned.

 

Or am I overlooking something?

 

I don't know. I can't see how you got your calculations. A back-of-the-envelope calculation I did shows that your fusion example would need about 250% of the ship to be reaction mass for the fusion engines--close to yours. That's assuming the weight of the fuel is calculated using 0.5g.

 

K.