|
Post by newageofpower on Jan 17, 2017 14:27:11 GMT
Resistojets are basically superior NTRs if you have the power budget already; if your fuel tanker runs 200GW power for MPD its better to use resistojet rather than NTR as the secondary drive.
|
|
|
Post by caiaphas on Jan 17, 2017 15:35:15 GMT
Resistojets are basically superior NTRs if you have the power budget already; if your fuel tanker runs 200GW power for MPD its better to use resistojet rather than NTR as the secondary drive. Really? I have some fine-tuning to do on mine, then, because mine aren't getting the performance of my mainstay decane NTRs. And do you mean superior in terms of dV or in terms of thrust-to-weight?
|
|
|
Post by teeth on Jan 17, 2017 15:39:19 GMT
You can get higher exhaust velocity out of them if you use a tantalum hafnium carbide coil because the melting point is so high, 7.5 km/s for methane in a resisto compared to 6.24 in an NTR.
|
|
|
Post by thorneel on Jan 17, 2017 15:48:37 GMT
Resistojets can achieve far greater temperature than NTR, as coil material has a higher melting point than fission dioxide. As such, they can achieve greater dV from the same propellant, while still giving high thrust. In addition, the engine itself is cheaper, lighter and simpler than a NTR, as power generation is not included in it.
So if you have unused power capacity, it is a better solution to use resistojets. In the above example, your 200 GW MPD tanker is going to sit on its power generation when not MPDing, so it makes sense to add resistojets for negligible additional cost, especially if you want higher thrust to escape gravity wells (or threats). Similarly, if you design your warship with a big power margin, it makes sense to use resistojets. My own laserstars almost always use resistojets, as I find simpler and more efficient to add some power generation and stick resistojets including for a non-modelled "industrial efficiency". Others find it more effective to be tighter on power and add NTRs. It may make sense to bring up pen and paper and actually calculate how the cost is balanced, including the lower dV per ton of propellant, for a given ship.
|
|
|
Post by newageofpower on Jan 17, 2017 16:46:43 GMT
On warships I prefer to bite the inefficiency and use NTRs for tactical propulsion, while my lasers use the X gigawatts my MPD was sucking up.
It is important to note that below certain energy thresholds (not quite certain where) the resistojet is less efficient than the NTR, but with our fleets of gigawatt spewing ships you should never encounter this problem.
|
|
|
Post by argonbalt on Jan 17, 2017 16:47:54 GMT
Hey so how hard do you think it would be to get a resisto jet up to 9.30/50 kms on a hydrogen diet?
|
|
|
Post by caiaphas on Jan 17, 2017 17:13:44 GMT
Hey so how hard do you think it would be to get a resisto jet up to 9.30/50 kms on a hydrogen diet? Well, I managed to make (an absolutely terrible, I'm getting a thrust-to-weight of only 123 g) an 11.1 km/s resistojet right now just be taking one of my decane resistojets and dropping the fuel flow rate, so probably not that hard. I think that around 15 km/s might be a hard limit, though (not based on any hard data, just a gut feeling), because I keep melting the coil if I try to drop it any further.
|
|
|
Post by bluuetechnic on Jan 17, 2017 22:21:32 GMT
One thing that might help advance the meta is to find out the operations behind various components, so we can calculate out and optimize our weapons and hopefully other systems too. Even if we don't design everything by mathematics, it could give us very valuable data on materials and designs, as well as a good starting point. I would compare it to finding out the frame data in fighting games, something that is pretty necessary to truly push the metagame, and by comparison we're playing a game about engineering which is in reality almost entirely about math.
I'm sure the calculations are in there somewhere, but as to exactly where I'm not sure. I also can't calculate things based on real numbers and equations, because 1.) they might be different, if only slightly from their real life counterparts and 2.) Many of the equations either use numbers we don't have access to, or worse they use calculations that aren't based directly on how they work in real life, like all of the energy weapons using constant power sources rather than capacitors.
So does anyone already know where they are, or should we start looking for them now
|
|
|
Post by kitten on Jan 18, 2017 7:12:38 GMT
On warships I prefer to bite the inefficiency and use NTRs for tactical propulsion, while my lasers use the X gigawatts my MPD was sucking up. It is important to note that below certain energy thresholds (not quite certain where) the resistojet is less efficient than the NTR, but with our fleets of gigawatt spewing ships you should never encounter this problem. Given the low weight of the resistojet proper (excluding its power source), you can even have MPD strategic propulsion, NTR main tactical propulsion and resitojets as auxiliary tactical propulsion (possibly side mounted, or as RCS or just for extra thrust in an emergency). If you consider the resistojet + reactor, it will always lose to a NTR. This is for a quite intuitive reason: the resistojet turns fission thermal energy into electricity into thrust, whereas the NTR converts the thermal energy into thrust directly. Obviously, the NTR can be made more efficient. However, if you're carrying the reactor anyway, the resistojet can offer performance similar to the NTR without having to take an additional reactor along. So the niche of resistos is thrusters you only use some of the time, on ships that already have high power requirements. P.S. as I understand it, the niche of chemical rockets in-game is very low endurance applications (for instance terminal guidance of coilgun-launched missiles). Basically whenever the mass of a fission reactor would be considerable compared to the mass of propellant, the simpler chemical rocket wins out.
|
|