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Did something significantly change with reentry heat in 1.1?


Mare Veris
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I have the feeling that managing the reentry heat is now much, much more difficult than it was in 1.0.5.

In 1.0.5 I've been playing with a normal difficulty, for the 1.1 I've started a new career (because I *knew* there would be bugs, I wanted to see all the new stuff, and - just a very, very little - I hoped for the "barn-style" level 1 base), but this time with "moderate" difficulty.

Where previously I would just make sure that I have enough parachutes, and I'm not diving down from the LKO at 90 deg angle, now I seem to need to consider adding a heat shield even for the Mk1 Command Pod, and really stress my fingers managing the ship orientation so none of the stuff attached to it (like that flat thermometer) burns in the atmosphere.

I see that the difficulty setting for the heat is the same as it is for a "normal" difficulty game, so it should not matter.

Is there so much changes in 1.1, is that some bug or imbalance, or my pilot skills got rusty sending yet another Kerbal with a rescue-to-a-rescue-of-a-rescue mission, and not really having time to bring them back?

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Yes, the MK1 parts in particular had tweaks, primarily drag / aero and now you'll plummet through the atmosphere with even a few extra empty tanks. You'll want to leave everything behind that you don't need before you attempt re-entry. Either remove experiments from modules (putting data/science in the pod) or transmit them. Note the MK1 Pod with nothing but a heat shield is quite aerodynamically stable and should have no problem slowing down on its own, at least reasonably within kerbin's sphere of influence. Here's some other suggestions;

  • Drogue chutes are able to deploy quite a bit higher up and with higher speed, they will slow you down enough for your main chutes (provided you can slow down enough to get them open).
  • Heat shields should be necessary with 100% re-entry heat. It's re-entry. It's definitely possible to bring an MK1, 2 goo cans, a set of drogues and a small chute in without a heat shield from LKO, FWIW, but you should get in the habit of packing one anyway.
  • Retro-burners or saving a bit of fuel in the last stage can slow you down dramatically. Even 300 dV is going to make most life-threatening entry a painless one. for that matter, gimballing engines can help you keep control when you're coming back in, even w 5-10% retro-thrust.
  • Finally, if you're bringing in top-heavy payloads without service bays, you may want to consider RCS to "strong-arm" yourself retrograde, to keep your instruments in a non-obliterated state.

Stock aero makes re-entry somewhat nerve-wracking again in 1.1 (so that's good), they may only need to tweak those settings to ease up slightly, but otherwise it's a nice challenge. I suppose its also worth mentioning that the expanding heat shield is allegedly OP and should keep most anything safe from burning up (haven't unlocked it yet to try)

Edited by Violent Jeb
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12 hours ago, KocLobster said:

I'm sorry I can't provide you a detailed explanation of what's changed, you'll need to wait for someone smarter than me to respond. I can confirm that reheating has gotten more difficult though, yes.

Almost exactly what I was going to say, only in fewer words.

I keep losing stuff attached to my Mk1 pods :/

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Also, having an "heavy" heatshield with 100% ablator resource is a good thing as it helps to stabilize the spacecraft in the shield-first attitude. And you can even jettison it later on the descent to make parachutes task easier.

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As a former DRE user I found it's not particularly difficult with stock reentry. My trajectories are always shallow and it takes several orbits to lower the Pe to the point of no return.

Just yesterday I was returning from Minmus at 3.5 km/s. The capsule survived but mystery goo canisters burned. I took another approach - put Pe down to 65 km and let the physics do the rest. Finally the capsule slowed to 2.3 km/s and I started the final descent (the Pe at the last orbit was at about 52 km). When I saw that I'm not making another orbit turn, I just used the remaining fuel to brake even further before I jettisoned them. At this point my speed was at about 1.5 km/s and nothing got burned. I lost less than 5% of ablator.

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Beyond just dropping weight and adding a heatshield or rockomax decoupler -- you can also go a different route, and make the aerodynamics work for you.

Try testing out the ship in this link, and think about applying a similar technique to your problem: 

 

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I'm primarily being burned on SSTO spaceplane deorbits... literally.

I have to figure out how to do them all over again. I do my standard shallow descent (I lower my orbit to 30 km on the opposite side of the planet, over KSC, and glide in full airbrakes. I generally don't even need to use the engines that way). Slight problem. Airbrakes or not... I'm not slowing down. In fact, I keep accelerating down to about 53 km... Only then I start to very slowly decelerate... WAY too slowly. I eventually disintegrate at around 40 km altitude, still going almost 2200 m/s. May have to hit the atmosphere at a much greater AoA and see if that helps.

For now, I worryingly enough cannot land my SSTO spaceplanes anymore... uhoh. Something definitely changed.

The fact that I usually use an extremely gentle deorbit is worrying me slightly though....

Edited by Merandix
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I haven't seen the problems some of you have with 1.1 and re-entry. 

I have been throwing some craft out to Duna and Eve and then coming back to Kerbin without making orbit and it just hasn't been a problem. I'm not doing anything special, just a mk1 capsule with a heatshield (200 ablative), setting the Pe at about 20km and holding retrograde on the way down. Not been getting close to overheating. 

Do you perhaps have a lot of junk sticking out?

SSTOs I point straight up during re-entry and use the wings etc as big air brakes. Not getting overheating issues then.  

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26 minutes ago, Foxster said:

I haven't seen the problems some of you have with 1.1 and re-entry. 

I have been throwing some craft out to Duna and Eve and then coming back to Kerbin without making orbit and it just hasn't been a problem. I'm not doing anything special, just a mk1 capsule with a heatshield (200 ablative), setting the Pe at about 20km and holding retrograde on the way down. Not been getting close to overheating. 

Do you perhaps have a lot of junk sticking out?

SSTOs I point straight up during re-entry and use the wings etc as big air brakes. Not getting overheating issues then.  

That's interesting. In 1.0.5, my interplanetary (and Minmus) re-entry Pe was generally around 29-30km. Could the fact that you're going straight through that 30-40km boundary quite quickly have something to do with the difficulties we're experiencing?

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A couple of days ago, I was returning my 2.2t probe from Mun flyby, with 2.5m heat shield strapped to the bottom of it, and Pe of about 35km. My Materials bay burned and exploded. Should I set lower periapsis perhaps?

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3 hours ago, 11of10 said:

A couple of days ago, I was returning my 2.2t probe from Mun flyby, with 2.5m heat shield strapped to the bottom of it, and Pe of about 35km. My Materials bay burned and exploded. Should I set lower periapsis perhaps?

Have a picture of the craft?

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On 4/27/2016 at 2:16 PM, Merandix said:

I'm primarily being burned on SSTO spaceplane deorbits... literally.

I have to figure out how to do them all over again. I do my standard shallow descent (I lower my orbit to 30 km on the opposite side of the planet, over KSC, and glide in full airbrakes. I generally don't even need to use the engines that way). Slight problem. Airbrakes or not... I'm not slowing down. In fact, I keep accelerating down to about 53 km... Only then I start to very slowly decelerate... WAY too slowly. I eventually disintegrate at around 40 km altitude, still going almost 2200 m/s. May have to hit the atmosphere at a much greater AoA and see if that helps.

For now, I worryingly enough cannot land my SSTO spaceplanes anymore... uhoh. Something definitely changed.

The fact that I usually use an extremely gentle deorbit is worrying me slightly though....

When I have problems with SSTO reentry (I use a path similar to yours), I point up above the horizon as if I want to climb.  Thus I use my lift to slow how fast a drop into the atmosphere.  That way, I keep my altitude high enough that I don't overheat until a slow down enough to drop lower.  If I decelerate slowly, then I drop into the atmosphere slowly.

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