Asteroid Redirect Mission

[Brandon Kerbin]

What sort to tips and equipment is required for an asteroid redirection? Parts? Delta-v requirements? Is there a point to doing one besides the coolness of it?

[Rune]

2 hours ago, Brandon Kerbin said:

What sort to tips and equipment is required for an asteroid redirection? Parts? Delta-v requirements? Is there a point to doing one besides the coolness of it?

There is a point: not launching fuel ever again. And coolness, that too.

Basically, they are giant flying fuel tanks (better than stock tanks at times, there are some with >90%fuel inside!), already full and in orbit. The second rock in the pictures? About 1,500mT of "free" fuel in LKO, for the price of launching a ~50mT miner that I have actually reused a couple of times already, then retired by taking it back down to kerbin (so technically, it was free fuel, I launched it on a SSTO). The trick is moving them to a usable orbit. To do so, you basically need a Klaw, good navigation skills, and a sufficient amount of thrust and/or patience. If you are smart about it, you can actually use the asteroid as reaction mass for the trip, if you pack a set of ISRU stuff (drills, refinery and radiators to keep things cool), and have a kerb up there to run things along (mining without engineers is about 100x slower these days).

 

Rune. And afterwards you can install KAS/KIS and turn them into amazing space stations.

[UnknowingTea]

Asteroid fuel is great, but note that there is a bug in KSP 1.2.2 that will give you trouble: 

Another great thing about asteroid redirect is that the contracts can be very lucrative in career mode. In my latest career, I have used a 100k craft to complete 500k+ contracts that require pulling a class D into orbit around Minmus. 

On the subject of coolness, this is in my list of the coolest things I have seen in KSP: 

 

[Brandon Kerbin]

What's a good ISRU setup that you recommend? The reason is I'd like to add a basic ISRU capability to a multipurpose lander/Explorer I have already built.

[Rune]

9 hours ago, UnknowingTea said:

Asteroid fuel is great, but note that there is a bug in KSP 1.2.2 that will give you trouble: 

Another great thing about asteroid redirect is that the contracts can be very lucrative in career mode. In my latest career, I have used a 100k craft to complete 500k+ contracts that require pulling a class D into orbit around Minmus. 

On the subject of coolness, this is in my list of the coolest things I have seen in KSP: 

 

Yup, it has to be a bug. But it's the reason I said "bring a kerbal or two to mind things". The bug only happens on unmanned stuff, put an engineer in there and the radiators will suddenly start working properly (or at least at 85% efficiency with a lvl3 engineer). Otherwise, the thing overheats until you are pulling ore at <0.1% the rate.

7 hours ago, Brandon Kerbin said:

What's a good ISRU setup that you recommend? The reason is I'd like to add a basic ISRU capability to a multipurpose lander/Explorer I have already built.

Well, you need at least a drill (the small ones will do, and putting many is counter-productive because you are limited by the converter speed), a refinery (use the big one so you don't waste reaction mass and can power the whole thing with fuel cells), an ore container of some kind, and enough radiators and electrical power (remember the asteroid will shade solar panels sometimes!) to keep things running nicely. Something like this, but attached to a manned ship that has the power to move around the big rocks:

 

Rune. Hummm I might try the fix now that you've pointed me to it, @UnknowingTea. Thanks!

[Sharpy]

Note: drill efficiency is affected by kerbal engineer level the same as on planets. So a craft with a three-star engineer will mine an asteroid 25 times faster than unkerbed. That's why you really don't want unkerbed probes to be asteroid tugs.

Another thing worth attention: equip your tug with mining equipment and you're unlikely to run out of fuel. Although the asteroid will arrive into LKO more or less depleted.

Also, instead of pushing the asteroid, pull it - it's way easier on the joints - just make sure there's enough clearance between the nozzle and the asteroid (two orange tanks length is safe for about all engines) or the exhaust will push into the asteroid not producing any thrust.

Most asteroids enter Kerbin SOI at stupid inclinations. Start the maneuvers months before encounter, and you'll be able to enter at equatorial orbit for some 100m/s worth of delta-V, versus a couple hundred needed in Kerbin SOI.

Autostrut the asteroid to root part, and save every time before you use time warp. The game really loves to rip the tug apart when reactivating physics.

[Rune]

15 minutes ago, Sharpy said:

Note: drill efficiency is affected by kerbal engineer level the same as on planets. So a craft with a three-star engineer will mine an asteroid 25 times faster than unkerbed. That's why you really don't want unkerbed probes to be asteroid tugs.

Only there is a bug, and untended drills overheat until they are working at <0.1% efficiency no matter the amount of radiators. So yeah, quite a bit more than 25 times faster.

15 minutes ago, Sharpy said:

Another thing worth attention: equip your tug with mining equipment and you're unlikely to run out of fuel. Although the asteroid will arrive into LKO more or less depleted.

Hardly. Even if you use a 100% propulsive capture with chemical engines, the total dV is not going to be much over 1km/s, and at a mere 350s (i.e: a Poodle, a fine engine for this job since it also has a respectable thrust), that's works out to a mass ratio of 1.33. Meaning you might expend at most 25% of the rock's fuel, worst case, unless you really screw things up. And you can use much less, using fancy tricks like gravity assist and/or aerobraking.

56 minutes ago, Sharpy said:

Also, instead of pushing the asteroid, pull it - it's way easier on the joints - just make sure there's enough clearance between the nozzle and the asteroid (two orange tanks length is safe for about all engines) or the exhaust will push into the asteroid not producing any thrust.

That used to be true, but then autrostruts happened, as you note. Solid advice if you don't use them, tough.

57 minutes ago, Sharpy said:

Most asteroids enter Kerbin SOI at stupid inclinations. Start the maneuvers months before encounter, and you'll be able to enter at equatorial orbit for some 100m/s worth of delta-V, versus a couple hundred needed in Kerbin SOI.

I like to use the Mun for that. Fixing inclination is where the big dV expenditure is ('cause aerobrake), so it's always nice when you manage to make the Mun pay the energy bill for you.

 

Rune. Note: in order to catch a rock in a solar orbit, the easiest way is to retrace its steps, leaving kerbin along the trajectory the rock will come in.

[Sharpy]

4 minutes ago, Rune said:

Hardly. Even if you use a 100% propulsive capture with chemical engines, the total dV is not going to be much over 1km/s, and at a mere 350s (i.e: a Poodle, a fine engine for this job since it also has a respectable thrust), that's works out to a mass ratio of 1.33. Meaning you might expend at most 25% of the rock's fuel, worst case, unless you really screw things up. And you can use much less, using fancy tricks like gravity assist and/or aerobraking.

If your asteroid had a lousy ore content, say, 80%, and you needed good 200m/s to change its really stupid inclination (say, it was detected too short a time for the encounter to prepare adequately early) - you'll end up with 50% of ore depleted. And you need to refuel the tug for another capture from that. Although, admittedly, my tugs are waaay oversized. Well, I worked around this by modding asteroids Since Class E would be both too easy and arrive too depleted to be usable, now I have a neat new&shiny Class G in Kerbin orbit

[Rune]

1 minute ago, Sharpy said:

If your asteroid had a lousy ore content, say, 80%, and you needed good 200m/s to change its really stupid inclination (say, it was detected too short a time for the encounter to prepare adequately early) - you'll end up with 50% of ore depleted. And you need to refuel the tug for another capture from that. Although, admittedly, my tugs are waaay oversized. Well, I worked around this by modding asteroids Since Class E would be both too easy and arrive too depleted to be usable, now I have a neat new&shiny Class G in Kerbin orbit

Mmm...

e^[(200m/s) * (1/9.8m/s²) *  (1/350s)]=1.059997...

So that means mass ratio of about 1.06 for a 200m/s maneuver on Poodles. Substitute 350 by your Isp for another engine. That means that to accelerate an object 200m/s, you need to expend 6% of its mass.

 

Rune. Just how heavy are your tugs, compared to the rocks they push?

[Sharpy]

29 minutes ago, Rune said:

Mmm...

e^[(200m/s) * (1/9.8m/s²) *  (1/350s)]=1.059997...

So that means mass ratio of about 1.06 for a 200m/s maneuver on Poodles. Substitute 350 by your Isp for another engine. That means that to accelerate an object 200m/s, you need to expend 6% of its mass.

 

Rune. Just how heavy are your tugs, compared to the rocks they push?

1200m/s - 1.41 

0.41/80% = 0.51

 

Dry mass 170 ton. 3.5m Nuclear reactor, 3.5m ISRU, two Tremor drills (each equivalent to about 5 stock drills), lots of tankage and a decent amount of ore (allows to kick-start production, ISRU heats up to optimal temperature way faster than the drills), active radiators to keep it cool, two Rhino engines. It could exert 30m/s on the Class G in one burn-refuel cycle. A smaller class E with some 80% ore content... it drained it to some 70% upon initial fueling, then brought it into LKO in one burn including a rather expensive plane change, then drained it dry fueling itself to 90% BTW, the delta-V display is bull. KER doesn't understand the new fuel crossfeed rules and believes the central column is a dead mass unavailable to the engines.

I'll have to get home and check the mass of that Class G, although...

A mix-up, scaling radius instead of mass, it's essentially a Class K. Full tank got about 0.3m/s. 

 

 

Edited January 24, 2017 by Sharpy

[Rune]

37 minutes ago, Sharpy said:

1200m/s - 1.41 

0.41/80% = 0.51

Dry mass 170 ton. 3.5m Nuclear reactor, 3.5m ISRU, two Tremor drills (each equivalent to about 5 stock drills), lots of tankage and a decent amount of ore (allows to kick-start production, ISRU heats up to optimal temperature way faster than the drills), active radiators to keep it cool, two Rhino engines. It could exert 30m/s on the Class G in one burn-refuel cycle. A smaller class E with some 80% ore content... it drained it to some 70% upon initial fueling, then brought it into LKO in one burn including a rather expensive plane change, then drained it dry fueling itself to 90% BTW, the delta-V display is bull. KER doesn't understand the new fuel crossfeed rules and believes the central column is a dead mass unavailable to the engines.

I'll have to get home and check the mass of that Class G, although...

 

A mix-up, scaling radius instead of mass, it's essentially a Class K. Full tank got about 0.3m/s. 

Ah, ok, gotcha, 1000+200, that makes more sense. Then again, 1,200m/s to catch a rock sounds quite high. I've gotten rocks around Mun for about 500m/s... accounting for all maneuvers and without aerobraking. But of course, that takes a lot fine navigation.

And yeah, you seemed to have scaled your game x10 with respect to stock. That is what I call a really heavy duty miner! By comparison, my latest is tiny:

.

As you can see, I carry the refinery as a module inside a bay (so I can leave it at the asteroid when I'm done and have a functional fuel depot), and the legs are provided by four drive pods with a nuke each. A whooping 240kN at a really high Isp, for maximum efficiency. I should still get ~100m/s out of each tank refill with your run-of-the-mill 1000mT class E. I like the fact that it is a repurposed general-purpose Magdalena class transport (MkII), with a few of my standard modules chucked in, plus a KIS container (which is where the drills are stowed). I'm getting all industrial-standardized on this.

 

Rune. I'm so running out of places to park them around kerbin, I'm thinking about building a KSO constellation just for the lols.

Edited January 24, 2017 by Rune

[Sharpy]

13 minutes ago, Rune said:

As you can see, I carry the refinery as a module inside a bay (so I can leave it at the asteroid when I'm done and have a functional fuel depot), and the legs are provided by four drive pods with a nuke each.

 

Uh. So modular. I'm getting modularity overdose. I don't quite see how that all acts together during push and afterwards. I'm not really a Transformers fan.

Also, after spending a week (real time) capturing a Class E with nukes, I really don't want to repeat the experiment. Although that was before autostrut and with ISRU running causing engines to throttle to like 5%.

 

1000 for a powered capture is quite normal. Aerocapture of asteroids... uh. Bad memories. Asteroids surface is quite uneven, sometimes in a way that acts as a turbine in atmosphere. You really don't want your Class E to enter 200RPM spin with a kerbed craft still attached.

Edited January 24, 2017 by Sharpy

[Rune]

19 minutes ago, Sharpy said:

Uh. So modular. I'm getting modularity overdose. I don't quite see how that all acts together during push and afterwards. I'm not really a Transformers fan.

Also, after spending a week (real time) capturing a Class E with nukes, I really don't want to repeat the experiment. Although that was before autostrut and with ISRU running causing engines to throttle to like 5%.

 

1000 for a powered capture is quite normal. Aerocapture of asteroids... uh. Bad memories. Asteroids surface is quite uneven, sometimes in a way that acts as a turbine in atmosphere. You really don't want your Class E to enter 200RPM spin with a kerbed craft still attached.

It is a bit complicated. But mostly because I am also trying to turn the potato into an asteroid base at the same time. See, the refinery module, the KIS container, and the cuppola tug, are meant to stay on the asteroid, docked to ports and stuff that is carried inside the KIS container, with the drills. The Klaw Pod is pretty obvious, you need a Klaw and it also moves the pieces around, with RCS and a hefty reaction wheel. And the Magdalena is basically the big buffer fuel tank that can keep the nukes happily fed during a long-ish burn, the fact that the nukes are on independent Drive Pods just means I can tailor the thrust to the mission (i.e: put more if I get too bored). Once on the asteroid, the refinery module and stuff can find their own anchors, and then I put the Klaw on the nose of the transport and push. A bit like this, which was the improvisation that led to the idea (an old unmanned miner had to be converted to manned because of the radiator bug):

And yeah, aerocapture can be tricky (though aerobrake can be rather sedate, over many orbits), but capture around kerbin can be free even without it, if you use the Mun, just like any necessary plane changes if you are a good enough pilot. As I said, fancy navigation tricks.

 

Rune. Doing this repeatedly has made me rather good at a) intuitively knowing how a gravity assist works, and b) fiddling with maneuver nodes.

Edited January 24, 2017 by Rune

[SapperChop]

This is my first post, and am not very experienced with forums, but I really enjoy building my asteroid station. I hope you enjoy the pics. Does anyone know how to "right" the camera to give a better orientation of the station (vertical)?

This station has a solar farm attached to the main hub using KAS. The panels originally only allowed sun exposure for about an hour of the day. 

Link to Screens: http://imgur.com/gallery/mC7eD

 

[Rune]

14 minutes ago, SapperChop said:

This is my first post, and am not very experienced with forums, but I really enjoy building my asteroid station. I hope you enjoy the pics. Does anyone know how to "right" the camera to give a better orientation of the station (vertical)?

This station has a solar farm attached to the main hub using KAS. The panels originally only allowed sun exposure for about an hour of the day. 

Link to Screens: http://imgur.com/gallery/mC7eD

 

Welcome to the forums! That asteroid station is pretty impressive. For the camera to work the way I want it to, I usually just control for a docking port that I want to face 'upward', and then I just use SAS and patience to make it point normal (north). For inclined orbits, its trickier and I usually eyeball it. you could also try switching camera modes with 'v' and see if any of them suit you for a given screenie.

 

Rune. The new SAS does wonders with humongous objects, if you give it time. I absolutely love that about it.

[Sharpy]

36 minutes ago, SapperChop said:

Link to Screens: http://imgur.com/gallery/mC7eD

 

Pretty. What mod did you use for the solar and fancy structures? What are these "bow" things on the solar module?

[SapperChop]

43 minutes ago, Sharpy said:

Pretty. What mod did you use for the solar and fancy structures? What are these "bow" things on the solar module?

The curved panels are from future solar. The habitats are from K&K planetry mods. I will get back to you on where the trusses came from! Thanks!

[SapperChop]

1 hour ago, Rune said:

Welcome to the forums! That asteroid station is pretty impressive. For the camera to work the way I want it to, I usually just control for a docking port that I want to face 'upward', and then I just use SAS and patience to make it point normal (north). For inclined orbits, its trickier and I usually eyeball it. you could also try switching camera modes with 'v' and see if any of them suit you for a given screenie.

 

Rune. The new SAS does wonders with humongous objects, if you give it time. I absolutely love that about it.

Thanks I'll try that out. I'm usually pretty impatient lol.