Jump to content

Deorbiting a class D asteroid on Kerbin


Recommended Posts

That is the contact in the title. 

Mission profile:

The spawned asteroid flies past Kerbin on a polar escape trajectory (about 90 degrees inclination). I can launch into polar orbit without problems from Woomerang, rendezvous and dock with the asteroid. I get into Kerbin orbit. 

Apoapsis is several thousand km out, periapsis is around 34km. After 4 aerobraking orbits it looks like the rock is going to stay in the atmosphere and land. Except I hit 10km at about 1200 m/s and hit the ocean at about 800 m/s destroying everything. 

The ship

4 Klaw grabbing units, 5 Nerv atomic engines, 5 reaction wheels, RCS, bells and whistles. I have attached about 20 drogue shoots and 20 normal ones. I don't have mining units because I have just enough delta v for everything technically. This is the ship that's supposed to push this rock around. 

How can I land the asteroid from low Kerbin orbit? It seems like my problem is with slowing it down enough. 

As a result, I haven't had a chance to test the parachutes. I have a feeling they might not work or they would yank the whole ship apart as they open. I started thinking on a concept to put together a probe core, Klaw, rcs and parachutes and send about 6 of them up on a second launch possibly with an engine attached to the side of the rock opposite the pushing ship. Rendezvous in low Kerbin orbit and use the new engine to slow down a bit more? 

I was excited to nail the mission up to the point of reaching the atmosphere but I am bummed by not being able to land it. 

Link to comment
Share on other sites

I recommend mining the asteroid. This removes a lot of its mass, while leaving its shape unchanged. Meaning, it will have a lower ballistic coefficient (mass in relation to drag), which in turn means it will slow down much better in the atmosphere.

If you don't want to do that, then you'll have to attach additional spacecraft with airbrakes, so that you can slow down enough for drogues to safely open.

Link to comment
Share on other sites

4 hours ago, MZ_per_X1 said:

Apoapsis is several thousand km out

In addition to @Streetwind's recommendation that you mine the asteroid, you may consider lowering your apoapsis more.  Your periapsis velocity (neglecting air resistance) is almost a thousand metres per second greater when your apoapsis is at a few thousand kilometres than it is when your apoapsis just outside Kerbin's atmosphere.

Link to comment
Share on other sites

  • 3 weeks later...

Guys, thanks so much for the comments. I managed to land that beast. I could get it into Kerbin orbit with periapsis at 45km and apoapsis at several thousand. I did about 40 aerobraking orbits trying to lower apoapsis to 2000km and just managed to get the periapsis back to 72km on the last drop of fuel. It was the most painful thing to do in Ksp.

As you recommended I sent a mining rig and I had to mine that thing silly. It still didn't float but did slow down enough to pop the parachutes. I feel elated. 

 

Lessons to learn :

Don't get alarmed that the ship's delta v drops to two digits after capture. Makes sense considering the combined mass of 700t. On Entry my asteroid was about 48t. I left 1% resource in it so it can be shared with other agencies.

I was worried how many expensive mining missions I need to send to empty that asteroid. One is enough because ***you can jettison the ore from the holding tanks***. They don't tell you that anywhere. So it's really about learning as you go. It took about an hour or so to take 90t from the asteroid so luckily that didn't take for ever. 

For some reason I don't trust asteroids when it comes to fuel transfer from one docked ship to another. It's probably user error but I couldn't refill the ship that I wrangled it to Lko in the first place. Never mind. 

Entry was shallow and only slowed down below700m/s below 10km. That gave me time to fiddle with the parachutes. They were deployed at 68km from the staging icons but they did not open so I actually had to stage them fearing that I would decouple the whole thing (which was the last stage). 

 

I would like to know how to disable a staged decoupler. 

Pure luck, I landed it on the North Pole. If I recover the ship, will the asteroid disappear? I want more of a memento than a surface sample. 

Oh and my Ps4 was really put to the test with this mission. 

I didn't make any kerbucks on it but got 65 reputation. Yay! 

 

 

Link to comment
Share on other sites

15 hours ago, MZ_per_X1 said:

If I recover the ship, will the asteroid disappear? I want more of a memento than a surface sample. 

I believe that it will disappear if the ship is still connected to it; asteroids are treated as a special category of vessel parts, so they are recoverable.  I don't know whether they are worth anything.  Be certain to disconnect any clawed parts and recover them separately if you should want a decorative rock accessory for your planet.

Link to comment
Share on other sites

17 hours ago, MZ_per_X1 said:

For some reason I don't trust asteroids when it comes to fuel transfer from one docked ship to another. It's probably user error but I couldn't refill the ship that I wrangled it to Lko in the first place.

From what I've read, KSP 1.10[.1] appears to have some issues with fuel transfers overall.

Asteroids usually allow crossfeeding (just imaging some pipework being laid across) and even crew transfers. My first asteroid fuel station ended up looking a bit like a pin cushion with refineries and tanks strewn everywhere:

Spoiler

thu1KRp.jpg

 

18 hours ago, MZ_per_X1 said:

I would like to know how to disable a staged decoupler. 

I don't think it's possible within the game. You could edit the .sfs file and set "stagingEnabled = False" for the part's "ModuleDecouple" module, although I'm not sure how to do that on a PS4 or if that is even an option.

Link to comment
Share on other sites

This thread is quite old. Please consider starting a new thread rather than reviving this one.

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...