The Orion's Arm Universe Project Forums





Possible acceleration systems
#4
Getting caught up on replies...

(06-29-2020, 05:54 AM)The Architect Wrote: Indeed, I had forgotten the details of what mass beams are and treated them like laser beams. The footnote article was quite interesting, although I have not read all of it, but I think I get a better sense of how it works. Do you think it would be possible to use collimated solar wind instead of streams of micropellets?

Unfortunately, no. The particles making up the solar wind move at about 400km/s while even the slowest 'practical' interstellar velocity (1% of c) is 3000km/s. In order to accelerate a ship up to the sort of speeds you are contemplating a mass beam needs to be moving at least as fast as the ship (or the final velocity of the ship) and solar wind just doesn't do that.

You could use a very large magsail (or lightsail, or lightsail/magsail combo) to get your ship around a solar system or even start it traveling out of a solar system before other systems take over. But using the solar wind or passive light pressure alone to get up to any kind of 'practical' speed isn't doable. Although if you wanted to do something where the ship takes thousands of years to travel between stars with the protagonist coming out of stasis or activating (if a sophtware or AI) only when the ship is in a system or there's an emergency, that would be doable.

Also, the infrastructure needed to make a Caplan thruster type system work seems to me to be at least as large, and quite likely larger, than what would be needed for a mass-beam based system.

(06-29-2020, 05:54 AM)The Architect Wrote: During flight, the ship needs to monitor the environment (although I don't think I need to get into details here), be able to make some level of course correction, resist to erosion, defend itself against hostiles. It can brake and accumulate energy by deploying a forward magsail towards the end. Ideally, it would run as fast as a Conversion drive or some drive of equivalent efficiency would permit. Ideally somewhere between 0.5 and 0.8c

Agreed, you probably don't need to worry about the details environmental monitoring on general principles, unless it plays a role in the story. Note that if the ship is potentially engaging in combat while in flight, being able to monitor the environment and detect incoming enemy ships/weapons could play a very important role in the story that could result in you needing/wanting to delve into this aspect of things more. But you know this project better than I so will defer to your judgement on this.

Course corrections in the realm of STL interstellar flight are doable, but take a long time. Given the already established use of magsails and such, your best bet might be to configure the magsail to interact unevenly with the galactic magnetic field to allow the ship to turn. Such turns will be very gradual (think years to decades to accomplish, depending on how much you want to turn), but in principle the ship could do a 180 given enough time. You can also in principle use this to generate electricity onboard. Like magsail based braking, this will also tend to slow the ship a bit, so this isn't something you can just use without limit. But its doable and the details may or may not be something you need to do a deep dive on.

Combat at interstellar speeds in a STL framework is not a topic that comes up a lot in SF. I/OA can offer some notions (and also contribute to the OA projects info on this since this sort of thing also applies to OA), but I'd also recommend seeing if Sevoris has some thoughts on it or can point you at relevant posts on the ToughSF blog. One of the biggest single factors may be the amount of kinetic energy wrapped up in the ships and how that can be used (or have to be defended against) in combat. Put another way - one of the most effective weapons in this kind of fight could be throwing a bag of gravel (or even just a bunch of glitter or a lightsail) overboard and slowing it enough so that your opponent then runs into it at high speed with an effect like a bunch of high explosives going off in their face.

Magsail braking can work very well, and works better the faster the ship is moving. I can point you at an article by Robert Zubrin about this. See HERE and the references at the end. Note that decel via this method starts out at multiple gravities and then drops off over a period of years (assuming high initial speed) and ceases to be effective once the ship slows down to about one half of one percent of the speed of light (1500km/s). After that you need some kind of other system to get down to 'interplanetary speeds' - rockets or some combo of rockets and other things probably.

In the OA setting, we presume that the Y11k versions of magbrakes can also operate as a ramscoop and collect/slow down/package and store interstellar material during the decel phase so that it can be used as reaction mass once the magbrake stops being effective. We don't have any hard numbers on this to share, but it seems doable. Using the energy generated during decel to make antimatter is a new (and fun) variant, but I'm not sure how much electricity you could actually extract or how much amat you might be able to make this way based on the energy available. That might be possible to calculate in terms of what the absolute physical limit is although the details could be left vague. And not sure you want to/need to get so much into the weeds to even calc the absolute limit for purposes of this story. Basically, it's an editorial choice on your part mostly.

In terms of the ship's velocity (.5-.8c) - Beamrider tech can do this in principle as long as you can keep the beam focused long enough. My preferred method is the 'smart dust' approach proposed by G. David Nordley in which a 'beacon laser' shines on the dust (which is actually a complex nanotech built construct) which in turn ejects parts of itself to push itself back into the focus of the beam. This system has limits (exactly how limited is open enough that you can partly make an editorial choice in this area), which generally mean the ship will want to accelerate hard at first and get up to cruise speed quickly while still close enough for the beams to work.

In terms of OA, for reaction drive ships with ramscoops, we describe using boostbeams to get the ship up to 'ramming speed' (the speed where the ramscoop works), then switching over to rocket drive using the scoop until the scoop is no longer effective (ramscoops have their own issues), then coasting until it is time to deploy the magbrake to slow down. This method has the option of only needing to get the ship up to ramming speed (generally ranging from 1% to 5% of c depending on who you ask) rather than all the way up to cruise speed. So your boostbeam energy and accelerator systems could be vastly smaller than those needed to get the ship all the way to .5-.8c.

In terms of drive specifics - Assuming you don't have conversion drive based on magnetic monopoles, you could use something involving antimatter (there are lots of designs). If you really want to push the limits of amat tech, I'd refer you to the q-mirror article HERE. Q-balls are a real think in RL theoretical physics and if you wanted to use a Q-mirror you could basically match OA monopole conversion capabilities or even exceed them in some respects depending on the details.

Ok - I think that about covers things for now.

Hope this helps,

Todd
Reply


Messages In This Thread
Possible acceleration systems - by The Architect - 06-29-2020, 05:54 AM
RE: Possible acceleration systems - by Drashner1 - 07-01-2020, 12:35 AM

Forum Jump:


Users browsing this thread: 1 Guest(s)