How to save my engines?

[goregonzola]

With the full release comes a new set of challenges and loving it all so far. Money is tight in career mode for me and I'm trying to recover my engines after separation as my launch involves a first stage separation that sends 4 Mainsail Engines tumbling back to the sea. I have staged decoupling and parachute deployment on each engine simultaneously but of course the chutes now burn up during re-entry. I tried to manually deploy each chute after re-entry but they don't (no electrics?).

I was hoping there was some way to do this where the chutes auto deploy at a certain height, remember I have had to stage them during decoupling.

Many Thanks.

[Red Iron Crown]

Welcome to the forums!

The stock solution to this problem is to add a probe core (and perhaps a battery if needed) to your engine module, which turns it into a spacecraft of its own right. You can then switch to it as it descends and deploy the parachutes when you like.

If you don't mind a mod, SmartParts has a timer that can stage your chutes for you.

In either case you must proceed a little cautiously. If your dropped engines fall too far into atmosphere and away from your focused vessel they will be deleted, chutes or not. Quickly get the rest of the vessel into a stable orbit, then switch focus to the engine module and follow it down.

Also, as this is more of a gameplay question I've moved it to the appropriate forum.

[KerikBalm]

Everything you decouple will despawn if below 23km in the atmosphere, and farther than 20km from your active craft (I think, it used to be 2.5km, but I hear the last update made it 10x as much)

As to the question of a timer, you can set the minimum deployment pressure to be pretty high... like 0.5 atmospheres.... that way your decoupled stuff should decelerate enough that when yoru parachutes deploy they aren't destroyed.

Just remember, they need to be touched down before your craft is more than 25km away...

or they need to stay above 23km (I think this is the critical altitude/air pressure) until you can switch your focus to them (ie your craft is in orbit, or at least has a very high apoapsis that will allow you to follow the boosters all the way down, before it reaches apoapsis)

[moronwrocket]

I follow the recommendations given by Kerik with a few extra:

1. Make sure you use two boosters. With 4 boosters you're more likely to have them spread out too far, ie the one closest to the planet will get pulled down and more than 22km away from the one furthest from the planet. Make sure you arrange the boosters so that when they detach they are at the same height above Kerbin, ie parallel to the ground.

2. Design your boosters so that they burn out and can be detached just before the circularization burn. Aim for a 100km orbit - this gives plenty of time for your main craft to circularize and to switch back to the booster group.

3. Transfer any remaining fuel out of the boosters to keep them light.

4. Put 4 radial chutes on the top of the boosters, in the same stage as the decoupler. Adjust to taste.

5. Change their minimum deployment pressure to the max. The chutes will activate with the decoupler, but hold off until well past reentry.

Or you could download and install Stage Recovery. Haven't done that yet but might if it gets annoying swapping to the boosters to watch them land.

[Laie]

Reposted from another thread, with minor edits:

The basics:

1. put a sufficient amount of chutes on the stage you want to recover.
   
2. toggle the chutes together with the decoupler
   
3. in a quiet moment, visit the tracking center
   
4. by default, debris is not shown. Mouse over the different icons to identify which is which, toggle debris on
   
5. select any debris from the list (or click on the map), then "recover"
   
6. PROFIT!
   
7. if there is no probe core or other command module, you will get no recovery dialog (and if there is, the parts will not be "debris", but a "probe"). But you still get money, just check your bank account before and after recovery.
   

The Problem:

Any pieces that are a) sufficiently far away from your active vessel, moving and c) too deep in the atmosphere, WILL BE DESTROYED. That means:

• You can easily recover the smaller solid rocket boosters that burn out early in your ascent. They can land safely before you get out of physics range.
  
• You can also recover very late stages that almost made it to space: after your vessel has circularised, open map view and look for the debris you care about. If it's still high in the atmosphere, you may switch vessels and watch it land.
  
• Any stages you detach in-between are pretty much impossible to recover.
  

Recovering late stages is a lot of hassle; besides, those tend to fall on the far side of Kerbin for very little recovery value. It can be done, though, and if you're the kind of person who wants to do it just because, you may find it quite enjoyable. Finding out how to safely land the debris is a learning experience, similar in scope to making your first orbit. Hint: the task becomes much easier if you're launching into a 100km orbit rather than the usual 70-and-a-bit.

Edited May 7, 2015 by Laie

[Red Iron Crown]

Laie, I think you missed a line in the OP:

I have staged decoupling and parachute deployment on each engine simultaneously but of course the chutes now burn up during re-entry.

I take that to mean the stage is being decoupled at a time when it has enough speed and altitude that it suffers reentry effects.

[amorymeltzer]

Check out Stage Recovery. It's pretty simple to comprehend and really easy to use, and the mechanics (higher speed and/or further from KSC = less $$) are just enough to make you thick about it.

ETA: The new version has some cool calculations to make re-entry heating relevant, which I haven't tried yet (workworkwork) but seems pretty nifty.

Edited May 7, 2015 by amorymeltzer

[Ulzgoroth]

You could try adjusting the opening conditions for the chutes. As I understand it, the min pressure parameter determines how much air is required before the chute will partially open. Setting that to a higher value should mean that, even though the parachutes have already been staged, they don't actually deploy until later in their fall. Set it to the right number and they should pop out after drag has slowed them enough to not destroy the parachute, though I couldn't tell you what the right number would be. You can also have multiple chutes with different settings for this so that they deploy sequentially.

If you have problems with the parachutes burning off before they deploy, try to make sure that the 'chute pods are tucked out of the airstream on the falling booster.

EDIT: This is theory, not something I've tested myself.

[Laie]

Laie, I think you missed a line in the OP:

Ooops. But Ulzgoroth already nailed it: setting the parachute to semi-deploy at 0.5 will trigger it at about 5000m above sea level. Most things should go sufficiently slow at that point, at least I haven't run into trouble yet (but I also haven't tried to recover really heavy stuff). If all else fails, add a probe core, battery and AIRBREAKS.

And yes, one has to like this. Otherwise, Stage Recovery will deliver the same result with much less trouble.