Low tech .90 recovery options?

[wumpus]

Scott Manley recently posted a video showing a low-tech (probably one step on the tech tree) 18T semi-recoverable rocket. While the specific rocket seemed impractical (I'd rather add two more SRBs in explosive staging than deal with the recovery issues for something that far away. Something tells me it won't cover the ~650 root cost of the SRBs), it shows at least some way to build a "space-X style" launcher in .90.

So far I have concentrated on single-liquid-stage+expendable SRBs to orbit. So to get to the Mun or something, I would dump a bunch of SRBs in the sea, get to orbit, de-orbit my booster as close to KSC as I can (hopefully around 95% recovery without mechjeb), and then go on my mission with the lander (which I might not be patient enough to bother aiming at KSC from the Mun). SSTOs might be more glamerous, but simply aren't going to go anywhere until you remove the weight restrictions on the launchpad (full disclosure: I have. My "bring more fuel for those stupid surveys" rocket just wouldn't quite work with the weight limitations, and I pretty much put every root into the buyout+rocket).

After watching the video (and failing to find the probe/debris with my copying attempts), I have to wonder how you go about "stay within 2.5km" are. Is a late gravity turn (to keep the booster closer to KSC) an option (I'm assuming you have to gravity turn with it to avoid a quick 2.5km distance). It looks like you *have* to take your booster above some [unclear, 30km?] altitude to keep theb parachutes from popping on the way up. After a few tries (mostly trying to make a medium lifter with a single asparagased pair of boosters) I checked the video again and the first [liquid] stage has 3000m/s deltaV (including 500m/s from the expendable SRB). This seems a long way from orbit (another 50% isn't "just a little more deltaV) but going to land a long haul from KSC (reason I want multiplayer: to hand this over to mechjeb with a small fraction of fuel and tell it to land on KSC. See how far it can go without a payload).

So, how efficient is it to dump a liquid stage a significant fraction of Kerbin's radius away from KSC? A rough guess of my recovery seems to be slightly more than half the cost of my rocket (the other half being SRBs and the lander). Anyone know how much you recover from the first stage when doing this? Scott Manley cut out the recovery screen, and it seems to be the critical number in determing if you want to recover as much as possible from a big booster or split the costs and lose a big chunk of a smaller booster (don't forget, a big low-tech and weight limited booster will have way too many SRBs hanging off of it. You don't get anything back from them).

Edited January 5, 2015 by wumpus
click answered.

[Dr-Drunk]

While I did enjoy watching Scott's video as usual I deffinitly wouldn't do it that way. For one you can design rockets to be even cheaper then his that perform most contracts just fine without worrying over recovery costs. My satellite launcher for example only costs about 10k or so and with contracts paying around 100k for around kerbin orbits money isn't an issue. Also.. There's a mod I believe called "Stage Recovery" or something (someone correct me on that if I'm wrong) but that allows you to recover stages as long as they had enough parachutes attached to the stage to prevent them from blowing up. The mod calculates this and basically gives you the money back as soon as the part unloads.

On a more technical note in regards to your question though... I believe the recovery rate at that distance from KSC would be around 85% of the cost of the tank minus the fuel. That can ofcourse be increased a bit with the administration office strategy but this also makes launches cost a bit more so yea.. But looking at where he decoupled the tank and it's last known trajectory it really didn't go that far away from KSC.

Quick edit on the post here:

Thought I'd put up the link to that mod I mentioned.

http://forum.kerbalspaceprogram.com/threads/86677-0-90-StageRecovery-Recover-Funds-from-Dropped-Stages-v1-5-3-%2812-22-14%29

Edited January 5, 2015 by Dr-Drunk

[Pecan]

SSTOs are easy - although LethalDose may be along to make it harder.

The T30 and Mk1 command pod, given 10-12 fuel tanks (tech-0) will be able to SSTO and land back at KSC.

Going to the moon there's really no point in taking all that stuff with you so, yes, you want to stage. Do it IN ORBIT, rather than dropping things back through the atmosphere on the way up.

So i) A vehicle that can go LKO <-> MuKO, ii) A simple SSTO rocket.

The amounts of money aren't really worth the time, but if you want to do SSTO then leaving the launch-vehicle in LKO is the only effficient way to proceed.

[Freak80MC]

There's a mod I believe called "Stage Recovery" or something (someone correct me on that if I'm wrong) but that allows you to recover stages as long as they had enough parachutes attached to the stage to prevent them from blowing up.

Thank you for that mod! I have been looking for a stage recovery mod ever since DebRefund was never updated, and you were finally able to deliver!

Edited January 5, 2015 by Freak80MC
Added a quote

[Pecan]

Erm, I'm going to assume some sort of reality - you don't need to SSTO, then decouple/undock. As long as one stage goes sub-orbital long enough for the other(s) to circularise before it gets auto-deleted you'll be able to come back to it, land and recover it and then go back to the one waiting in orbit.

[wumpus]

It looks like I'll stick with my single-[liquid]-stage-to-orbit [ignore all those SRBs hanging off of it], but with odd tests of this "other" method. One thing I tried was going asparagas with the idea that the side stages could make it to orbit on their own if sufficiently throttled. Testing made it appear that they weren't stable under thrust, maybe I'll have to try with autopilots capable of maintaining a prograde heading (I thought they weren't using the autopilot/SAS system they had). This would be more or less an ideal method (except for that whole three landings per launch. Probably have to hand it over to mechjeb).