Spacecraft question

[garrowolf]

I am working on my fusion age game in Nexus D20 and my brain is too tired from work this week to think straight. I want to have the ships have a high acceleration rate 10-20 gs with everyone in shock gel and controlling the ship through VR. The problem is that I can't think of a good justification for the ship to have a high Acceleration and a fairly low burn endurance. Fuel wise would that be a bad idea or would it be basically the same as a low acceleration/high burn endurance engine?

 

[Umbran]

Broad generalization - a high-power engine will be less efficient than a low-power engine.

On the other hand, a low-power engine must be in longer continuous operation (and thus need to be more durable) than a high-power engine.

 

[tomBitonti]

Broad generalization - a high-power engine will be less efficient than a low-power engine.

On the other hand, a low-power engine must be in longer continuous operation (and thus need to be more durable) than a high-power engine.

Umm, perhaps some of the parts (e.g. control circuits and such) don't need as much durability, but other components (e.g., exhaust nozzle, high speed pumps) will need to be very well built to operate at high power. Wouldn't the trade off between high and low loads, with issues of non-linearity, allow a lower power engine to deliver much much more power over its service lifetime than a high power engine?

Thx!

TomB

 

[Stormonu]

If the ship is using something akin to nuclear explosions to propel itself, there's your justification for high acceleration. Radiation output/accumulation then might become a reason for short burns.

Likewise, for ship control, have you considered "mind control" instead of VR, akin to the latest fad of games that use cranial eletricity to control/maneuver objects (such as [ame="http://www.amazon.com/Star-Wars-Science-Force-Trainer/dp/B001UZHASY"]here[/ame])?

 

[garrowolf]

Well the VR would connect to the crew through neural induction so yes.

I like the idea of shorter bursts because of radiation. That's a cool idea. I was planing on using Fusion Torch engines so it should work perfectly!

 

[Umbran]

Wouldn't the trade off between high and low loads, with issues of non-linearity, allow a lower power engine to deliver much much more power over its service lifetime than a high power engine?

This one *is* rocket science, so it gets complicated very quickly.

Small point on definitions. "Power" is "energy per unit time". A low-power engine can't deliver more power. It is, by definition, low power. How long you run the engine doesn't change the power.

But yes, a low power engine, over its lifetime can deliver more energy. This is what the ion engines NASA's playing with these days are all about, in fact. And, yes, it may be that the durability of parts in the low-power engine winds up not being an issue, as the lower power often means much, much lower stress and wear on parts.

In reality, the choice of what engine to use depends on what you plan to do with it, what technologies you have, and what fuels you can use. If you're really "blue sky", there's no way to tell you which is better or which is worse. For fiction, you have to externally apply some restrictions in order to make a decision.

 

[Stormonu]

Just putting this out for the heck of it...sometimes it's good to think just beyond what's available in technology, and to ponder how humanity interacts with that technology...

The sci-fi setting I've been developing, Romeworld, is on the verge of the graviometic age. At this time the vast majority of ships run on fusion torch; colonization has gotten as far as the asteroid belt and there are several projects underway at Jupiter looking at extending colonization to the remainder of the sun-starved planets with plotting for colonization of other systems. By means of cutting edge gravity devices, Mar's orbit is now fixed to parallel Earth's (so there is no variance in travel distance through the months). Mars has been mostly terraformed, but sometimes suffers from tectonic plate shifts induced by the alteration to it orbit.

A ship running at full burn can traverse the distance from Earth to Mars in about 3 months. However, due the limits of ship's stores, fuel and crew psychology (ships tend to be cramped and available food is dehydrated & prepackaged) and physiology (artificial gravity is too expensive and bulky for starships except for the largest warships or pleasure cruise ships), most ships make the trip in up to 6 months time. There are "waystations"/space stations set at intervals along the way to facilitate travellers. Known as the Marium Causeway, it's similar to the way towns sprang up along railroad routes in the old U.S.

However, one of the latest projects being tested near Jupiter is known as the HyperGun. This is a gravio/magnetic "launch tube" that is being tested primarily for eventual use in intersystem travel. It consists of the Hypergun and a "net" to catch objects. It can obtain speeds up to .95C (with hope they can get it up to .97C once it's out of beta testing) Currently, the designers are trying to work out a serious flaw in the system - they have devised a ship that can survive the rapid acceleration and deceleration, but they have yet to been able to design an accelerometer system that can react fast enough to prevent living objects from being pulped by the speeds that are obtained.

 

[Umbran]

The sci-fi setting I've been developing, Romeworld, is on the verge of the graviometic age.
....
By means of cutting edge gravity devices, Mar's orbit is now fixed to parallel Earth's (so there is no variance in travel distance through the months).

Um, if you have gravity devices on planetary scale (especially that big - you may not understand the amount of energy you'd need to maintain the scenario you're describing - it is equivalent to having an entire planet "under thrust", permanently), you don't get to claim the culture is "on the verge" of the graviometic age.

(artificial gravity is too expensive and bulky for starships

You have fusion torches. You don't need artificial gravity. Just arrange the deck so that the torch pushes up on people's feet, and so long as you're under thrust, you've got "gravity".

However, one of the latest projects being tested near Jupiter is known as the HyperGun.

You realize that whoever owns this device owns the solar system, right? Hitting a planet with a largish object going 0.9C or better is an extinction-level event.

 

[mmadsen]

I recommend reading Winchell Chung's Atomic Rockets site from (virtual) cover to cover.

 

[garrowolf]

[MENTION=33447]Storm[/MENTION]omu I think that you have your tech levels mixed up there. Moving a planet is a very high tech level solution and there are a lot of lower tech solutions. Terraforming would take a long time and you would have at least a few tech levels during that process.

This is the tech level break down that I am using and I think it is pretty good:Nexus Tech Levels - Nexus D20 Wiki

I put rearranging solar systems at tech level 15, and artificial gravity at 11. Keep in mind that once you have artificial gravity you also would likely have inertial compensators so that your crew is not effected by the acceleration in the first place. They would be both effects of controlling gravitic fields (assuming that it is possible in the first place).

There is also a huge leap from colonizing the outer planets to colonizing another solar system. It is a few orders of magnitude higher (AUs to light years to kiloparsecs).