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2 hours ago, Laie said:

May I inquire about comets? The wiki still lacks information about them, and this here looks like a good place to ask.

a) how do I find them? If I enter the tracking station at game start, it doesn't take very long for a small population of Asteroids to turn up. Will comets work in the same way, only  requiring more patience? Or is some kind of player action required to trigger their appearance.

b) what kind of mass do I have to expect? The screenshot above shows a 50,000t comet -- do we already know whether that is one of the lighter or heavier ones?

I believe they can be found by both the tracking station and SENTINEL scope, they're just rarer. If you fire off a few SENTINELs in a solar orbit past Dres (?) it should turn up a few comets.

As for size, I believe the largest comets are Class-I, as in I for Isabella. Class-I are always on an interstellar trajectory (to my knowledge) and are massive, although I can't find any concrete numbers. The one in the screenshot above is a Class-G, which is two steps down from I. For comparison, regular asteroids only go up to Class-E, which can be up to 4000ish tons. Not sure if comets can be asteroid sized, or if it's A-E for asteroids and F-I for comets with no overlap.

 

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@SomewhereOutInSpace: thanks.

I started looking and it seems that perhaps one in ten objects discovered in the tracking station is a comet. They're quite obvious: while asteroids are clustered near Kerbin, comets turn up elsewhere. I could spend a hundred words describing it, but they really stick out from where they show up.

So far I found one class E (of similar mass as an E class Asteroid), one class G (40,000t when I visited), and one class H (191kt).

Unlike Asteroids, their mass appears to be fixed at the moment they fist show up in the tracking stations -- I got exactly the same mass on two visits to the same comet. With asteroids, you can saveload: they only get their mass when you first get into physics range -- or at any rate, it was such when I last caught an asteroid in KSP v1.7.

I see resource concentrations in the usual range, 80-90%, but it seems as if comets cannot be mined: The drill shows a "Start Comet Harvester" button, but pressing it only wiggles the drill for a moment before it deactivates on it's own. No Ore is being mined.

As my drill nearly touches the surface even when retracted, I don't think it's a matter of it not getting deep enough.

Mining worked on the next attempt with a different vessel.

ETA: crossposting this to Gameplay Questions.

 

Edited by Laie
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Mining comets is wonky due to a bug with the drills - looking at the drill configs, it appears the new ModuleCometHarvester (why they couldn't just use asteroidharvester since they're mechanically identical I have no idea) was straight-up copy-pasted by SQUAD from the small drill to the large - hence the large drill having incredibly short range and low yield on comets.
 

Edited by SuicidalInsanity
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On 7/26/2020 at 10:53 PM, SuicidalInsanity said:

Mining comets is wonky due to a bug with the drills - looking at the drill configs, it appears the new ModuleCometHarvester (why they couldn't just use asteroidharvester since they're mechanically identical I have no idea)

Well, a new module gives them the ability to make things work differently, for better or worse. I've tried drilling a comet and it looks as if the comet doesn't actually lose mass, even though the data in the PAW says so.

This dramatically reduces the dV you can get from mining the comet, by about half. You also don't get the benefit of a steadily increasing TWR.

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2 minutes ago, Laie said:

Well, a new module gives them the ability to make things work differently, for better or worse. I've tried drilling a comet and it looks as if the comet doesn't actually lose mass, even though the data in the PAW says so.

This dramatically reduces the dV you can get from mining the comet, by about half. You also don't get the benefit of a steadily increasing TWR.

Fortunately it seems like this is a bug. Mining a comet and having the overall mass increase obviously violates the law of conservation of mass.

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On 7/26/2020 at 4:35 PM, OutInSpace said:

As for size, I believe the largest comets are Class-I, as in I for Isabella. Class-I are always on an interstellar trajectory (to my knowledge) and are massive, although I can't find any concrete numbers. The one in the screenshot above is a Class-G, which is two steps down from I. For comparison, regular asteroids only go up to Class-E, which can be up to 4000ish tons. Not sure if comets can be asteroid sized, or if it's A-E for asteroids and F-I for comets with no overlap.

Comets are class E - I according to the CometDefs.cfg in the GameData/Squad/Resources folder. So the class E overlaps for comets and asteroids. There are 4 types of comets:

  • short (class E-F)
  • intermediate (class F-H)
  • long (class G-H)
  • interstellar (class G-I)

The short, intermediate and long seems to refer to the period of the comet.

The smallest comet I've seen so far was 1.622 kilotons (class E), the largest was 763.089 kilotons (class I).

A class I comet cheated onto the KSC:

Spoiler

EzpQ8vV.jpg

 

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13 hours ago, EveMaster said:

Comets are class E - I according to the CometDefs.cfg in the GameData/Squad/Resources folder. So the class E overlaps for comets and asteroids. There are 4 types of comets:

  • short (class E-F)
  • intermediate (class F-H)
  • long (class G-H)
  • interstellar (class G-I)

The short, intermediate and long seems to refer to the period of the comet.

The smallest comet I've seen so far was 1.622 kilotons (class E), the largest was 763.089 kilotons (class I).

A class I comet cheated onto the KSC:

  Hide contents

EzpQ8vV.jpg

 

I am thinking of what I can do with getting an interstellar comet into solar orbit. My guess that it will take the largest spacecraft that I have ever made. It's on the list but not right now...

I think I am going to focus on my first Eve Crew mission

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So, let's do some math. Delta-V values dependent on propellant fraction ore concentration:

ISP

80% 90% 95%
340 (Rhino) 5370 7680 9990
380 (Wolfhound) 6000 8580 11150
800 (Nerva) 12600 18000 23500

This neglects the mass of the hardware you're sending, but that shouldn't make much of a difference.

For all practical purposes, you're limited by your mining and ore conversion rate. A maneuver of 250m/s will consume 3% of the vessel mass at ISP=800s, and 7% at 340s. Even with a rather lightweight G class of 25kt, that resolves to 750t or 1750t, respectively. That's a lot of propellant. Either you bring enough tanks to store the required amount, or enough converters to create it on the fly, or any combination thereof. By and large, converters (incl. fuel cells, radiators, drills) are way more mass efficient than stocking up on tanks.

If the Wiki is to be trusted, one drill per converter will be good down to 30% concentration for chemicals, or 10% concentration for nukes. It takes 1.2 converters to provide for a single nuke,  5.4 converters for a Wolfhound, or 32 for a Rhino. These numbers assume a 5-star engineer.

More numbers in the spoiler.

Spoiler

Nominally, one converter recipe (not sure how to call it) will require 30EC to  produce 5kg of propellant, per second. With a  5-star engineer (125% efficiency), that becomes 37.5 EC and 6.25kg.

The drill is supposed to generate 5 units of ore (50kg) per second, multiplied by concentration and engineer. So the ratio of drills-per-converter is the same at any kind of engineer level. At 10% concentration, one drill will provide enough ore to drive one converter recipe.

Thermal requirements are flat regardless of what level of engineer you have: 200kW for every recipe you're running.

An engine's fuel flow can be calculated as (thrust / (isp * 9.81)). That's how I arrived at 7.65kg/s for a LV-N, or 100.6kg/s for a Wolfhound. Divide by 6.25 and you have the number of converters needed.

Operating a Rhino also requires 20 large radiators and approx. 150 Gigantor Panels or ~220 large fuel cells, and when running on fuel cells you need 2-3 more converters just to provide for the fuel cells.

Up to now, I've only detected comets when they were already inside of Dres' orbit, often even inside Duna's. Unless you get really lucky with Kerbin's position at the time, you can only reasonably rendezvous with them after they went through their PE. Placing Sentinels beyond Jool may give more of an early warning, though I don't know how useful that will turn out to be in the end.

The typical mission profile will probably include maneuvers at high solar AP, followed by gravity assists near Eve or Kerbin or Jool, possibly several of them.

Edited by Laie
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29 minutes ago, Laie said:

The typical mission profile will probably include maneuvers at high solar AP, followed by gravity assists near Eve or Kerbin or Jool, possibly several of them.

What about a Kerbin aerocapture? It'd take some trial and error, but the comets are so massive (and therefore draggy) that you could probably do it with one relatively high pass. That way you just need to get it onto a Kerbin encounter.

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1 hour ago, Laie said:

If the Wiki is to be trusted, one drill per converter will be good down to 30% concentration for chemicals, or 10% concentration for nukes. It takes 1.2 converters to provide for a single nuke,  5.4 converters for a Wolfhound, or 32 for a Rhino (also 20 large radiators and approx. 150 Gigantor Panels or ~220 large fuel cells, and when running on fuel cells you need 2-3 more converters to provide for those).

Thanks for doing the math. What distance to the sun did you assume for the Solar panels calculation? After reaching the periapsis, the comet will move quickly away from the sun. Will the total power generated by covering the whole comet with solar panels be enough to extract and convert all ore to fuel assuming you start to mine at periapsis? For capturing an interstellar comet you only have one try. Fuel cells might be an option if the solar power is not enough.

 

1 hour ago, Laie said:

Up to now, I've only detected comets when they were already inside of Dres' orbit, often even inside Duna's. Unless you get really lucky with Kerbin's position at the time, you can only reasonably rendezvous with them after they went through their PE. Placing Sentinels beyond Jool may give more of an early warning, though I don't know how useful that will turn out to be in the end.

Comets will always spawn between Duna and Dres. In CometDefs.cfg the spawn distance from the sun is defined as 1.5-2.5 semi major axis of Kerbin. Duna has an orbit of around 1.5 Kerbin SMAs and Dres about 3.0.

 

1 hour ago, OutInSpace said:

What about a Kerbin aerocapture? It'd take some trial and error, but the comets are so massive (and therefore draggy) that you could probably do it with one relatively high pass. That way you just need to get it onto a Kerbin encounter.

For an interstellar comet the chances are very slim that it might come close to a planet on its path so that a aerocapture or gravity assist might not be an option. For a normal comet or an interstellar comet that has already been captured it might work. Smaller comets will be easier to capture though. The mass of a comet increases with the cube of the radius. The cross-sectional area increases only with the square of the radius. The drag is proportional to the cross-sectional area so the larger comets have a smaller drag to weight ratio, making them harder to capture. A comet that has been mined of all its ore will also be easier to aerocapture. If the comet breaks apart during the aerocapture, the remaining parts will also be smaller and easier to handle.

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16 hours ago, EveMaster said:

What distance to the sun did you assume for the Solar panels calculation?

Nominal output, that is, Kerbin distance. And 100% insolation. Good luck with that.
 

16 hours ago, EveMaster said:

Will the total power generated by covering the whole comet with solar panels be enough to extract and convert all ore to fuel assuming you start to mine at periapsis? For capturing an interstellar comet you only have one try. Fuel cells might be an option if the solar power is not enough.

Probably not, but I don't think that's entirely necessary. Once you're seriously past PE, time is no longer quite as essential. You can afford to do several mine/burn cycles where mining happens in timewarp. Even more so at AP.

The need to do very long burns is most urgent near solar PE or when trying to capture at Kerbin.

I'd still recommend to not rely on solar panels, though: covering the whole comet with solar panels will be a lot of work to begin with, keeping them oriented towards the sun can be a PITA, and for all that your capture burn may be interrupted by entering Kerbin's shadow.

16 hours ago, EveMaster said:

Comets will always spawn between Duna and Dres.

Good to know, thanks -- I won't even try the Sentinels then.

17 hours ago, OutInSpace said:

What about a Kerbin aerocapture?

A long long time ago I tried to aerocapture a large asteroid. It had a nasty tendency to spin and tumble, exposing my tug that was supposed to ride safely in it's slipstream. Boom. Also, comets are said to break up in the atmosphere.

Edited by Laie
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18 hours ago, Laie said:

Good to know, thanks -- I won't even try the Sentinels then.

Excuse me quoting myself, but interesting tidbit: the more Sentinels you have, the more objects you can track. With the tracking station alone, you can expect to discover perhaps two comets a year, but if you place a number of sentinels, anywhere really, you can track more objects overall and hence are also more likely to turn up a comet.

I'm looking for a comet that's just right, so I though this would be useful...

Very quickly, I had veritable clouds of asteroids both near Kerbin and Eve. Some of these would receive the weirdest gravity assists, tossing them to Jool and beyond, giving me a lot of false positives on my quest for comets.

I'll try putting the sentinels below Moho next. If that still doesn't work to my satisfaction, I'll look into editing the cfg... but no sooner.

I also consider readying several redirectors, and parking them in the Asteroid cloud that is soon to engulf Moho. Just to have a craft on the ready when and if a suitable comet shows up.

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2 hours ago, Laie said:

Excuse me quoting myself, but interesting tidbit: the more Sentinels you have, the more objects you can track. With the tracking station alone, you can expect to discover perhaps two comets a year, but if you place a number of sentinels, anywhere really, you can track more objects overall and hence are also more likely to turn up a comet.

Thats true. But the number of found comets seems to go up slower than the number of found asteroids. If there are already comets around the comet spawn chance is reduced. If you have dozens of Sentinels running you end up having over 1000 untracked asteroids and the game becomes very slow. So I advise you to disable the tracking for the sentinels once you have found the comets you searched for. If you disable the sentinels the number of untracked asteroids goes down with time and the game runs fast again.

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I performed a mission to an interstellar comet (and other space objects) and back.

From a waiting orbit at Dres to the insterstellar comet an back to Kerbin it took me 27.5 km/s with a lot of gravity assists on the way back.

I guess redirecting an interstellar comet to an orbit is really hard. You have to be really quick, if you want to reach it with all your equipment  before the comet is beyond the reach of the antenna.

 

Edited by EveMaster
posted in wrong thread
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3 minutes ago, EveMaster said:

I completed my submission for round 3. My space craft, the CometChaser goes to

Huh, round 3? Visiting many? I thought this was about redirecting one...?

Be that as it may, have my upvote. And a thousand thanks for taking the time and converting your pictures to jpg.

 

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4 hours ago, doggonemess said:

What I don't get is how to position the craft so you can actually maneuver or change the velocity of the comet. I tried grabbing it right over the center of mass and all it did was tumble when I started the engine.

When docked, unlock the connector, target the center of the comet and lock the connector again. I find that often the SAS does not a good job at targeting the center of the comet, so I target it manually and enable SAS once the connector is locked.

With a locked connector the comet and all docked spacecraft are considered one craft. To turn it you need a lot of reaction wheels or RCS thrusters.

Shorter rockets make it easier to push the comet. You might also try to pull a comet with a frame that has rockets attached on the sides. The frame must be larger than the comet, so that the rockets fire to the sides of the comet and not against it.

Edited by EveMaster
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On 8/2/2020 at 3:06 PM, EveMaster said:

I performed a mission to an interstellar comet (and other space objects) and back.

From a waiting orbit at Dres to the insterstellar comet an back to Kerbin it took me 27.5 km/s with a lot of gravity assists on the way back.

Did you use part mods to get that much delta V?

 

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On 8/3/2020 at 3:56 PM, doggonemess said:

What I don't get is how to position the craft so you can actually maneuver or change the velocity of the comet. I tried grabbing it right over the center of mass and all it did was tumble when I started the engine.

Many possible reasons, starting with not hitting the CoM to begin with. Flex in the joint and excessive gimbal action is another common culprit.

I'd recommend to take it to Gameplay Questions with a screenshot, or perhaps a short video.

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Still torn. The mining bug hasn't been fixed yet, so the comets won't lose mass -- it's still totally possible to do it with the dV you get from mining, but acceleration won't ever pick up.

More generally, I don't see myself targetting anything bigger than a F class, or perhaps a lightweight G. Not with stock parts, at any rate -- but if I start scaling up converters and adding big-S nuclear reactors, this becomes just as easy or hard as any asteroid redirect mission.

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Does anybody know what‘s the crash tolerance of a comet? If it‘s high enought and we manage to enter Kerbins atmosphere with an comet, we could „land“ it. But it would be a very hard landing...:D

Edit: Unless it breaks apart...

Edited by s_gamer101
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1 minute ago, s_gamer101 said:

Does anybody know what‘s the crash tolerance of a comet? If it‘s high enought and we manage to enter Kerbins atmosphere with an comet, we could „land“ it. But it would be a very hard landing...:D

Edit: Unless it breaks apart...

The crash tolerance seems to be nearly infinite. I let a class I comet crash into Tylo at 3000 m/s and the comet survied. It even survives some times when I put it onto a retrograde Jool orbit and let it crash into Tylo straight on at 5000m/s. It seems that a comet can only be destroyed by a crash if it ends up to deep in the ground within a simulation step. It also survives being dropped from orbital height into the Mohole. It would require about 10 layers of class I comets to fill it up. :D

Not sure what the tolerance against atmosphere is. The comets tend do break up into multiple smaller parts when the speed is to high and these parts then explode.

OKLmOnP.jpg

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Well I know what I want to do next. Looks like I am going to be doing A comet base. The inspiration actually comes from Star Wars Spaudrons.

Specifically this map

Nadiri Dockyards | Wookieepedia | Fandom

Of course I would want to redirect it into a more stable easier to approach orbit...

I first have to choose a comet size but first Eve Crew mission

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