how hard is it to use a stationkeeping drive as a transit drive?

[glitterboy2098]

basically what it says in the title. how difficult is it to use the 1/10th g stationkeeping drive that jumpships and space stations have to transit within a solar system?

[cray]

It's not hard, and it's covered in the StratOps' system transit rules. You just have to multiply normal 1G transit times by 3.17 (the square root of 10).

Compared to any engine invented through 2024, 0.1G in deep space is fantastic. You can reach Pluto in about 2 months, or go from Sol's standard points to Terra in 27 days. Mars isn't 9 months away like for our probes on Hohmann transfer orbits, it's about 9 days (at 1AU).

[glitterboy2098]

and there wouldn't be any drawbacks to running a drive for months at a time?

[AlphaMirage]

and there wouldn't be any drawbacks to running a drive for months at a time?

It already runs frequently in order to keep station relative to it's home point.

[Kerfuffin(925)]

I think for jump ships it’s the fact that most carry small amounts of fuel more than anything. And they generally have limited cargo to carry a second round of fuel.

[AlphaMirage]

I think you could use a dropship tug to put a space station into an Aldrin Cycler type orbit.

[glitterboy2098]

ok some related questions.

can you dock dropships to a spacestation while it is using that tenth of g to transit?

and can primitive dropships with no KFboom use station docking collars?


for a worldbuilding project i'm doing, i'm trying to come up with some options for large transit vehicles for moving around distant parts of a trinary system, in a society that lost the ability to build jumpships.

[AlphaMirage]

As I recall you can dock under such low thrust but you don't need it running all the time either once you get in a good orbit.

I believe that is forbidden but they can dock to cargo doors.

You really should look up Aldrin cyclers, there's a bunch of good YouTube videos about it. Isaac Arthur has a bunch of other options too including laser sails which could also exist in btech

[glitterboy2098]

aldrin cycler would be too slow in this case.. i'm currently looking at feasibility for getting to the more distant sun in the system, which would be about a 5th of a lightyear trip. according to the travel time calculator i found, even with 1/10th g constant thrust you'd be looking at nearly 3 years one way.

getting between the two main stars (which range from only ~36 to 12 Au apart) would be comparatively easy, it would just need good sized fuel tanks on regular dropships.

[AlphaMirage]

How fast do you need to get there?

Perhaps the far star is like the penal colonies of Dredd or frontier and under developed on purpose. You have say six-ten of these cyclers and they arrive every 4-6 months to pick up new 'colonists' and drop off frontier guards.

Or you just don't develop that solar system and focus effort on the binary . Otherwise you could push it with droptugs to a higher speed, it just makes transfer windows shorter.

[cray]

and there wouldn't be any drawbacks to running a drive for months at a time?

They already run for years at a time.

can you dock dropships to a spacestation while it is using that tenth of g to transit?

Docking hard points (be they cargo bay doors or actual collars) are not meant to carry attached ships while under thrust. You'd need dropshuttle bays.

and can primitive dropships with no KFboom use station docking collars?

The boom doesn't matter for normal docking. Use a cargo bay door as a docking spot. StratOps clarified that doors are suitable docking points.

i'm currently looking at feasibility for getting to the more distant sun in the system, which would be about a 5th of a lightyear trip. according to the travel time calculator i found, even with 1/10th g constant thrust you'd be looking at nearly 3 years one way.

Sounds correct. A 0.1G drive could do that.

Note that BT fusion engines went to high thrust levels pretty quickly. The Magellans were launched in the late 2020s at 2Gs for interstellar flight.

getting between the two main stars (which range from only ~36 to 12 Au apart) would be comparatively easy, it would just need good sized fuel tanks on regular dropships.

Sounds like you're modeling it on Alpha and Proxima Centauri.

I think you could use a dropship tug to put a space station into an Aldrin Cycler type orbit.

If you have BT fusion engines then cyclers are painfully slow. In 2027, the Columbia made the trip to Mars in 14 days. Shortly thereafter, the Magellan probes managed 2Gs for months at a time. In comparison, cyclers often have years-long cycles between two planets. 0.2 light-years would have cycler flight times in terms of millennia.

[Giovanni Blasini]

I think for jump ships it’s the fact that most carry small amounts of fuel more than anything. And they generally have limited cargo to carry a second round of fuel.

Yup.  Your most common JumpShip in the Inner Sphere, the Invader, will burn through 1.975 tons of fuel per day while flying in transit.  Its fuel tanks are only 50 tons, though.  The good news is that it's got two cargo bays of approximately 288 tons each, and so can easily devote some of that to extra fuel to make a transit, or even an emergency fusion-powered KF jump (around 197.5 tons) possible.

[AlphaMirage]

If you have BT fusion engines then cyclers are painfully slow. In 2027, the Columbia made the trip to Mars in 14 days. Shortly thereafter, the Magellan probes managed 2Gs for months at a time. In comparison, cyclers often have years-long cycles between two planets. 0.2 light-years would have cycler flight times in terms of millennia.

Yes, but if you can't make jumpships or 'large enough' dropships you need to move mass some other way and that way is space stations and hollowed out asteroids. That way is just slow.

Also, could it be adapted? I think it could, just shove it in the right direction with a little adjustment thruster to make small corrections en route and catch it when it gets there.

Again, how fast do you need it to get there?

[cray]

Also, could it be adapted? I think it could, just shove it in the right direction with a little adjustment thruster to make small corrections en route and catch it when it gets there.

For the proposed star system: a cycler or Hohmann transfer orbit crossing 12AU would take about 7-8 years one way, never mind the full cycler orbit. 36AU would take 50 years one way. 12,600 AU (0.2 light years) would take about 5,000 years one way.

Again, how fast do you need it to get there?

Probably faster than 5 millennia. 

Even the shortest crossing of 7-8 years would demand a very large vessel to support a crew for that length of time. Fusion actually lets you shrink the ship because travel time drops down to months at 0.1G.

[glitterboy2098]

Sounds like you're modeling it on Alpha and Proxima Centauri.

i am, mostly because it is the only one i could find that both had a lot of good data on the system structure available to the public, and has some proof that planets exist around one or more of the stars (Proxima has one confirmed planet, iirc, and there is a currently unverified detection of one around Alpha Centauri a)

plus the orbits of the two central stars are far enough away that you can have worlds within their habitable zones, without having to worry that the two star's close approach would wreck them. though i'm sure that day/night cycles get a little weird during the years of close approach.

you can't really justify gas giants though alongside the normal planets, but mining such is a fun trope i want to include. sticking one around the distant companion would fit, and make for a neat detail. and if it takes a huge "mobile space station" vessel to do so and return with useful amounts of resource-cargo, that's a neat feature.

[idea weenie]

i am, mostly because it is the only one i could find that both had a lot of good data on the system structure available to the public, and has some proof that planets exist around one or more of the stars (Proxima has one confirmed planet, iirc, and there is a currently unverified detection of one around Alpha Centauri a)

Watch out for the Mind Worms

plus the orbits of the two central stars are far enough away that you can have worlds within their habitable zones, without having to worry that the two star's close approach would wreck them. though i'm sure that day/night cycles get a little weird during the years of close approach.

you can't really justify gas giants though alongside the normal planets, but mining such is a fun trope i want to include. sticking one around the distant companion would fit, and make for a neat detail. and if it takes a huge "mobile space station" vessel to do so and return with useful amounts of resource-cargo, that's a neat feature.

What are you mining that makes it worthwhile to send cargo stations back and forth like this?

[Paul]

What are you mining that makes it worthwhile to send cargo stations back and forth like this?

Probably plotonium, might also be handwavium. He wants a system that works that way, so it works that way.

[Daryk]

Germanium is the most valuable element in BattleTech, last I checked... :)

[cray]

Germanium is the most valuable element in BattleTech, last I checked... :)

At less than 1 C-bill per kilogram? KF drives without docking collars set sort of a maximum for germanium prices.

[Daryk]

Value and in-universe price are often disconnected... ;)

Seriously... Germanium is the sine qua non of FTL travel.

[cray]

Germanium is the sine qua non of FTL travel.

I'm learning all sorts of new words this week. "Basic," "extra," and now "sine qua non." Gen Z lingo is crazy. ;)

[Daryk]

Sine qua non is Gen -2 at least... Latin FTW! ;)

[glitterboy2098]

germanium is also not going to be as valuable if they lack KF drives.
i was thinking things like helium 3 (which while not needed for fusion in BT, could easily be needed for various industrial processes), with perhaps some of the noble gasses like argon or xenon (which at least IRL, tend to be found in much higher concentrations in the gas giants than on earth)

admittedly that bit is kinda more nebulous, since i didn't want to develop the idea too much until i knew the feasibility of the hardware side of such trips. and i might be able to handwave in a gas giant in a closer orbit than the tertiary star.

[AlphaMirage]

You could also have some Lostech piece of equipment made by DoME there.

One that say could transmuting elements into more valuable elements but its placed within a dyson ring or something similar so it can harvest the necessary power.

No one wants to live out there but it is a potentially very valuable piece of equipment that you could use and might be worth the trip for long duration scientists and their support staff.

[Paul]

One that say could transmuting elements into more valuable elements but its placed within a dyson ring or something similar so it can harvest the necessary power.

Making a dyson sphere requires tech massively in excess of what the star league is capable of. Thousands of years of tech advancement, materials that are stronger than atomic bonds alone, and the ability to transport dozens of entire planets from multiple nearby solar systems to process in to the shell.
Then the device to transmute materials would be ludicrously more advanced still. ST level magic.

Whatever you're playing at that point, it's got absolutely nothing to do with BT anymore.

[AlphaMirage]

Perhaps but we are also talking about a setting that regularly rapidly terraforms planets. Connected by KF superluminal drives scheduled by radio broadcasts through weird physics. One that also has canon giant constructs made of strange, super advanced materials and for a time fairly good AI. It is not impossible that like Niops the Star League had other scientific outposts or that a detached settlement could evolve in a different way from a strong knowledge base.

I did also say ring not sphere, it could even be a swarm. It just needs to be something difficult to make and useful enough to warrant regular trips between it and the main binary. Since it is only a few light-years it would've been easy to jump there if you had a ship.

[Paul]

Perhaps but we are also talking about a setting that regularly rapidly terraforms planets.

A trivial and routine activity done as a school project by the time you're making dyson spheres. Or rings.

It is not impossible that like Niops the Star League had other scientific outposts or that a detached settlement could evolve in a different way from a strong knowledge base.

Sure. But the tech required for what you speak of requires them to advance to an extent we can't even dream of, and then also find the time to grind down literal planets needed to get enough materials for the job.
Whoever these gods are, they stopped caring about K-F a few thousand years ago.

I did also say ring not sphere, it could even be a swarm.

OK, so now you just need to move and grind down all the planets and asteroids in the solar system you're in. Definitely easy than moving some a couple of light years.

It just needs to be something difficult to make and useful enough to warrant regular trips between it and the main binary.

I understand that goal, but I'm trying to indicate you've overshot the mark by a few millennia and light years. The technological gap between us and the people who built the pyramids is much smaller than the gap between us and the people who could make a dyson swarm.