this post was submitted on 14 Jan 2025
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How do you re-enter with heavy vehicles? (e.g. carrying 4 tourists) (aussie.zone)
submitted 1 month ago by Zagorath@aussie.zone to c/ksp@lemmy.world
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I'm trying to re-enter from orbit after ferrying 4 tourists. My general strategy has been to burn retrograde from my periapsis (which is at ~71 km) until the new periapsis is about 35 km. But no matter how I steer, I haven't been able to get it low enough to even deploy drogue chutes

I also tried a strategy where I put antennae on both of the tourist pods, and separate parachutes on each, and decouplers between the two of them and before the command pod, with the intention of all 3 landing down separately. A week ago, this worked for me on a flight where the tourists only wanted to enter space. But right now, coming down from orbit, every time I try this they seem to crash...but only if I'm not observing them. They come down at a safe speed and the parachutes clearly do deploy, but then upon touching down...they're not available to collect, and the mission is failed. I even tried switching to one of them, and then the command pod disappeared instead.

I suppose there are two questions in this: (1) how can I slow down a 3 tonne vehicle enough with fairly early tech to safely deploy the parachutes? (2) What do I need to do to make sure I can properly track separate craft after they land down?

Screenshot of KSP showing 9 techs researched, all in the first 4 tiers.

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[–] Gurfaild@feddit.org 8 points 1 month ago

The easiest way to do this contract with your tech is probably to take the tourists on two separate flights - use only one crew container per rocket and take half the amount of tourists. You could also replace the command pod with a probe core to save mass, or try increasing the drogue chute deployment altitude to 5000 m if you haven't already.

Any vessels that fly in atmosphere and are out of physics range (used to be 2.5 km, but I can't remember if that's still the case) from the active vessel are destroyed by the game, so the pods were probably deleted before hitting the ground.

[–] rescue_toaster@lemm.ee 7 points 1 month ago (2 children)

Strange. I've landed ships almost identical to that. You aren't forgetting a heat shield, are you? Maybe try a higher periapsis, like 45k-50k?

[–] Zagorath@aussie.zone 3 points 1 month ago (1 children)

I don't have a heat shield. I'm not quite entering fast enough to need one to avoid burning up. Would a heat shield help slow down faster, too? If so, how would I ensure the craft can face retrograde to point the heat shield forward?

[–] rescue_toaster@lemm.ee 4 points 1 month ago (1 children)

I guess I'm confused as to what's going wrong then. I assumed you were blowing up due to heat. Are you going too fast for the drogue chutes? Do they rip off when you deploy? I don't think I've ever had a problem with not slowing down enough to deploy drogues.

When you come in, you do want to be retrograde. If I remember correctly, with that vessel, it will come in a bit sideways, heating up the crew capsules, but still should be okay.

[–] Zagorath@aussie.zone 3 points 1 month ago (1 children)

Oh I see. Sorry, I guess I could have explained the scenario a bit clearer. But yeah, no issues with blowing up due to heat. It gets quite close to that, but even though I actually enter and try to stay facing skyward as long as possible (to present maximum surface area to the wind, and slow down as much as possible—at least I assume that's how the physics should work), the craft survives until it slams into the ground. Eventually I'm not able to keep it facing skyward and the physics forces it to face anterograde. idk if adding a heat shield to the bottom would add enough mass to that end for it to fall retrograde instead.

Unfortunately it never seems to deploy the drogue chutes, but I'll take a closer look next time I'm able to play the game; maybe they are deploying and ripping off. How do I tell?

[–] rescue_toaster@lemm.ee 5 points 1 month ago (1 children)

Are you actually deploying them via staging? They should be staged before your main chutes. You still need to press spacebar for them to deploy.

If the icon is red, you are going too fast and they will simply rip off when you press spacebar. But from your scenario, i would guess you lose enough speed for the icon to turn yellow and then grey, when it is completely safe to deploy.

[–] Zagorath@aussie.zone 2 points 1 month ago (1 children)

If the icon is red, you are going too fast and they will simply rip off when you press spacebar

I thought that a red icon will cause them to wait and not deploy until it is safe? That's how I've usually done it in previous successful flights, anyway.

This is what it looked like shortly before crashing on my latest attempt (where I set periapsis to 46 km from an apoapsis of 71 km). It didn't slow enough to deploy before I crash landed.

[–] rescue_toaster@lemm.ee 2 points 1 month ago (1 children)

Are you sure those are drogue chutes? Perhaps they need to be staged separately. I just cheated a similar vessel into orbit and had no issues on re-entry to 45k periapsis. They turned yellow at about 700 m/s and I pressed spacebar to deploy. They were staged separately and before my main chutes.

[–] Zagorath@aussie.zone 2 points 1 month ago (1 children)

Are you sure those are drogue chutes?

Yup. I've got two radially-mounted Mk2-R Radial-Mount Parachutes, two radially mounted Mk12-R Radial-Mount Drogue Chutes, and the Mk16 Parachute as the nosecone.

I tried again with a 48 km periapsis (71 km apoapsis, IIRC) and still crash landed. I tried the separate staging idea and no luck. It stayed red the whole way down.

[–] rescue_toaster@lemm.ee 3 points 1 month ago (1 children)

Well I am confused. You're under 600 m/s which should be safe. I literally tried it last night and deployed fine at 700 m/s. Maybe just try to deploy the drogues anyway when you get under 700 m/s and see what happens? Did you change any of the parameters of the drogues? I don't remember what the defaults are.

[–] Zagorath@aussie.zone 2 points 1 month ago

I actually just managed to get it to work, after adding radially-mounted radiator panels to help add some drag. I think the drogues only deployed at 500 m/s, which I reached at about 3,000 m above ground, so really the last moment before a crash. You can see the parameters I was using in the screenshot above, which I think was intended to allow it to deploy earlier than the defaults.

Out of interest, were you using orbit speed or surface speed? A difference of about 200 could be explained by you using orbit speed when I'm using surface.

[–] Jumuta@sh.itjust.works 1 points 1 month ago

actually this is the correct solution, i seriously just forgot that heat shields would be unlocked by this point haha

[–] Jumuta@sh.itjust.works 6 points 1 month ago (1 children)

the second problem is kinda a ksp limitation, it's because the second craft exiting the simulation distance and getting MIAed. you can kinda solve this by using physics range extender (mod), but it'd be pretty finicky.

I guess what you could try to do is attach a bunch of small 1.25m parts (empty fuel tanks?) below the 2 crew modules and point retrograde in reentry, basically using them as sacrificial ablator

[–] Zagorath@aussie.zone 3 points 1 month ago

attach a bunch of small 1.25m parts (empty fuel tanks?) below the 2 crew modules and point retrograde in reentry, basically using them as sacrificial ablator

At the moment, I don't especially need ablator, unless that would somehow actually help with slowing down (would it?). I actually entered pointing skyward until aerodynamics made that completely impossible and forced me to face anterograde. Some parts were experiencing heat stress as a result, but not enough to be destroyed, and I figured that angle presents the largest possible surface area to help slow down the most; it still didn't slow me down enough.

[–] Mandarbmax@lemmy.world 3 points 1 month ago (1 children)

Some small wings and control surfaces might help you slow down, belly flop into the atmosphere instead of pencil diving. Maybe glide a bit if you really have to to burn off speed.

[–] Zagorath@aussie.zone 3 points 1 month ago* (last edited 1 month ago) (1 children)

I tried adding some wings but they caused the craft to repeatedly flip during take-off.

I actually had already tried belly flopping into the atmosphere with just the craft as shown in the OP. I stayed that way until eventually aerodynamics took over and I was physically unable to do anything but pencil dive for the last stretch.

edit:

That's how I had the fins configured, fwiw

[–] Mandarbmax@lemmy.world 3 points 1 month ago (1 children)

You will be able to prevent flipping during launch if you either put the top stage in a fairing to cover the wings or if you put bigger wings on the bottom. maybe experiment without wings that are upside down but idk if that is a problem or not.

Let me know how things go!

[–] Zagorath@aussie.zone 3 points 1 month ago (1 children)

I don't think I have any fairings unlocked yet unfortunately.

I didn't see this comment until now, but I did just manage to get it to work after adding radial radiator panels, which I think acted similarly to the wings to add just enough drag to let me deploy the drogue chutes.

[–] Mandarbmax@lemmy.world 3 points 1 month ago (1 children)

Awesome! Glad you cracked it!

[–] Zagorath@aussie.zone 3 points 1 month ago

Thanks for all the help!