How to: Falcon-9 style booster without the panic

[Blaarkies]

TL;DR

How to launch a payload into low Kerbin orbit, but recover the booster stage without any mods or 30 second time windows where you have to stress to get the thing in orbit.

This is simple, but to pull this off you will need to be confident in you skills to launch into orbit somewhat efficiently, to land a tube booster, and obviously design the whole thing.

The idea here is that we do not have a barge to land on...so we make the KSC the barge. No need for a boostback burn, and more than enough time to switch view to the payload and sort that out. The fast shallow trajectory also helps out the second stage to require less dv.

1. Launch from the Desert launch pad. You may need the breaking ground DLC for this
2. Aim East for a trajectory that hits beyond the KSC with an Apoapsis of 70-100 km
3. At 60km, deploy the payload
4. First, control the booster. Do any correction you would like to, so that the trajectory hits past the KSC, somewhere around the Island Runway
5. Switch craft to your payload, and set a maneuver on AP to circularize
6. Stay with the payload craft, burn the maneuver
   1. Expect about 400 m/s dv, and 0.3+ TWR
7. As soon as PE is at 70+ km, switch back to the booster
8. With the booster, aim retrograde, toggle Navball to surface mode, extend the heatshield bow shock extender (just a tiny heatshield on a Breaking Ground DLC piston)
9. Below 1000 m/s speed, you can open any landing legs or airbrakes
10. Pop parachutes as training wheels to make it all easier (probably even saves more fuel this way)
11. Land safely, and recover (before walking away)
12. Switch back to the payload craft in orbit, and continue its mission

 

1. - Launcher.  Built from1.8m parts, with 6 Thud engines at the bottom. Launch due East, as if going to a shallow low orbit

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2. - Trajectory to KSC. This time I missed the 90° heading mark, so it went a bit South. No worries, we can easily fix this

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3. - Deploy the payload. It works to start rotating the booster backward during this deployment, it separates them a bit.
Notice the altitude and velocity. The payload is almost in orbit, it doesn't need much more to get there

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4. - You can worry about the payload later, first go back to the booster

The camera might automatically switch to the payload when you stage the decoupler

• The booster needs a little course correction. In my screenshot, I would hit too far south, so I burned a bit towards north until the landing spot was inline with the KSC, slightly past the Island Runway
• Waiting to do this step later just makes it more expensive

This payload is a re-usable 2nd stage fuel transport. It gets ~4 tons of LFO into orbit. The engines are hidden using BG motors to hide them inside the cavity during re-entry.

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5. - You have 3+ minutes to sort out the payload orbit.  0.22 TWR should do the job fine, but you can go for 0.5+ TWR for the first few tries

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8. - Get to the booster before the atmosphere does, and you will have no worries at all. Point the flamey end down where it ought to be.
This screenshot was done after I finished my Caveman Challenge NCD career, where all difficulty settings are at max for anything that makes it harder, including 120% re-entry heating.
On the 1.25m booster, I had no heating issues because the speed is only 1800 m/s. But with this 1.8m booster, the heating bars frequently almost maxed out, so I added a heatshield that
extends out in front of the engines. Small price of drag to pay going upwards with such a large vessel, but the heat protection is excellent.

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The worst of the heating is in this screenshot

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11. - A drogue chute for early safety, a normal chute to do most of the slowdown. Set the Navball to standard SAS (else it will follow retrograde and could tilt over)
Even with chutes, the descent might be about 20-30 m/s. Much too fast for a landing. Use engines to slow it to 5 m/s. The chutes prevent a violent splashing.
This lands fine on land as well, but water is always flat, so...

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For the low price of fuel + fairing-shell (and 3% tax), we just put a 5 ton payload in orbit. Land on the KSC continent and you will still get 90% returns on the booster

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12. - Now go back to the payload, and do the mission that it was destined to do.

 

This technique has made it possible for me to tripple my contract career profits, because I'm playing with the 10% funds rewards setting (did I mention the NCD Caveman Challenge?). 
So everything I launch has to be perfect, or else it eats into the budget that doesn't exist. Using this idea I have been building a 40-50 ton Duna station in orbit that is supposed to also return some Kerbals. The contracts associated with it will bring in about 300k, but I'm sure that disposable boosters for such ship will easily cost 150k. I have spent a little over 30k so far, and this is now on a Fly By course with Eve at the moment.

The downsides to all this

• Your payload will end up in a 7-9° inclined orbit. That is fine if that is where your station is, but it only costs 100-200 m/s dv to fix that, even less if you combine it into the circularization burn
• Extremely inefficient use of booster size. Such a huge booster can easily launch more than a measly 5 tons to orbit. But the launch is nearly free, so it is still many times cheaper even if you have to launch 3 times
• It is hard to do. It took me a few tries but then I got the hang of it. I bet any KSP veteran will struggle on the first try, but it gets easy after the first few tries. It is still harder than normal launches now, but it is easier than doing 2 normal launches (if I had to do those to recoup the funds lost due to disposable boosters)

 

 

 

 

 

 

 

 

Edited December 23, 2021 by Blaarkies

[RickInAZ]

3 hours ago, Blaarkies said:

the heating bars frequently almost maxed out, so I added a heatshield that
extends out in front of the engines. Small price of drag to pay going upwards with such a large vessel, but the heat protection is excellent.

Thanks for this tutorial. This looks like it would be fun to try!

How did you add a heat shield that extends "out in front of the engines"? I see it in the image, next to the engines, but I don't know how to install a heat shield in that location.

[Blaarkies]

Thanks, I hope you nail the landing 

For the heatshield thing, I used the Breaking Ground DLC, it has these robotic pistons that can extend/retract when you activate them. I just placed the heatshield on top of that, and gizmo-clipped the assembly upwards into the rocket body.

I set the action group key to the "Brakes" action, this way when i toggle brakes on, it extends the heatshield out beyond the engine nozzles. Just remember to retract it again before firing up the engines again, since they will burn and explode the heatshield.

In-game, this trick works because of a quirk where the most heating gets applied to the most forward part of a rocket. I learned it from some some youtube video from either of the KSP gods (Bradley Whistance, or Stratzenblitz?) explaining it on a spaceplane surviving ridiculous speeds just because the heatshield poked out in front. For our booster, we hit the air bottom first and need it there instead.

There is a real life effect that matches this though, but I have no idea if it is equally useful