Tribute: Tesla to Duna

[sevenperforce]

I created this challenge yesterday:

And I just managed to complete it.

I didn't score all the possible points, but I did successfully complete my main goal, which was propulsively landing all three booster cores within the same save. It's very challenging. The trick is to use a highly lofted initial burn, followed by a flat boostback on the first booster, an even-more-lofted boostback on the second booster, and a high-apogee downrange loft on the core. If timed properly, each booster can be landed before the following booster drops out.

I suppose it doesn't look very Tesla-esque, but oh well.

It can do about 50 mph, so we'll just chalk that up to it being a little on the old side.

Corners ridiculously well, though, thanks to the low center of gravity.

It survived this jump, surprisingly, though I believe it lost a headlight.

Then came time to mate to the rocket!

It's a big rocket. I could have made it smaller with Tweakscale, but didn't want to use mods.

The Roadster takes its rightful place.

The three cores are virtually identical, except for the fairings up top. Not shown: nine Vectors, thrust-limited to 92% (because Falcon Heavy will launch Elon's Tesla at 92% of its max thrust), with 100% gimbal on the core engine and 75% gimbal on the circle of engines.

Time to head to the pad!

Sitting pretty.

Ignition before clamp release. Each of the 12 landing legs are an aligned pair of landing struts covered by elevons (with control authority turned off), keyed to the gear action group. 

"Check ignition
"And may God's love be with you..."

Starting a very, very mild turn at 100 m/s.

Going to have a very lofted trajectory.

At around Mach 1, I used an action group to cut thrust on all but the core's center engine. It's not perfect; the real Falcon Heavy will throttle all nine engines down to the minimum throttle together, but I couldn't be QUITE that perfect.

Up, up, and away! I would have liked to use a reskin but oh well.

Cutting all engine thrust to around 65% at 500 m/s to help loft the trajectory a bit more.

Coming up on staging. The goal will be to separate and flip the first booster for boostback as soon as possible after apoapsis exceeds 70 km; that's when I know I'll be able to switch back and forth without problems.

Am I correct that the navball automatically switches from Surface to Orbit as soon as your apogee exceeds 70 km? I suppose I'll have to test that another time. Anyway, it was the indicator I used.

MECO and stage sep! Action groups are your friend.

Leaving the core engine firing until I clear the two side boosters. I would have liked to have a single RCS thruster set to "fore by throttle" connected to a single monoprop tank, just to aid in separation, but there's no good way to do it.

The core engine will fire until I am 2.5 km out of range, which should give me a bit of a loft.

Using the engines to help with the flip on the first booster.

The trick here is to get as flat a boostback as possible, but still keep my apoapse over 70 km so I'll be able to switch to the other booster in the brief window of time that I'm officially out of the atmosphere. 

All right, this boostback is almost done.

Waiting to be able to switch back to the other booster...

This one takes a much more lofted boostback burn, because I need a bit of hang time. I will only have a few seconds after I land the first booster before the second one would unload.

Lofted boostback on the second booster, complete.

Rapidly switched back to the core; I'd already crossed apoapse so I really have to gun these engines to get back onto a good trajectory.

After getting my core to the desired trajectory, it was back to the first booster...with just seconds to spare.

Already dropping like a rock. Used action groups to turn off the ring of outside engines but manually reactivated two of them for the three-engine burns to come.

The first booster has a very gentle entry and doesn't need an entry burn.

Landing burn starts pretty high, though. These engines are still limited to 92% thrust.

I would have liked to come down closer to the beach, but I'll take what I can get. Booster is transonic.

I'd toyed with using the airbrakes for control, but it never really worked right so I just made them fixed.

Made sure to switch to radial-out at the right time; otherwise you end up going haywire at landing.

Opening up those elevons and lowering the legs.

Legs down; final approach. Throttling for landing.

Dropping throttle lower.

This will be a perfect hoverslam.

And down! Still wobbly, but safe. 

And again, with seconds to spare, I switch to the next booster core.

This time I'm already in re-entry while I'm switching my engines back on.

Despite a higher-energy entry (given the more lofted boostback), I didn't need an entry burn on this one either.

Starting the landing burn at roughly the same altitude; drag is the great equalizer here.

Subsonic. Should have good fuel reserves.

Still firing full-throttle.

Legs down early this time...not really possible in real life, due to drag on the legs, but the drag from my airbrakes is so much higher than leg drag here that it doesn't matter.

Less slam, more hover.

I had enough fuel to counter gravity losses; my real concern was getting down fast enough to get back to the core before it hit the atmosphere.

Made it!

Couldn't resist a glamour shot with this core here and the other one in the distance. 

I really should have used Tweakscale to bump up the authority on the RCS thrusters, but I wanted to do it pure-stock.

Uh oh; the core (and upper stage) have already dropped out of the atmosphere. This is going to be REALLY tight.

Glad I didn't blow that fairing earlier.

Boosting the upper stage free as soon as possible.

I'm going to let the upper stage burn on its own while I switch back to the core. The engine will continue to fire until there is 2.5 km between the two vehicles; then the engine firing sequence is unloaded even though the vehicle persists on its trajectory. With luck, this will be just enough to get out of the atmosphere, but not so much that I waste all my fuel.

Back to the core, switching to my three recovery engines.

On this one, I'm DEFINITELY going to need an entry burn. (Spoiler: I tried without one, and most of the engines survive but all the airbrakes burn up.)

"This is Ground Control to Major Tom
"You've really made the grade"

Thankfully it doesn't take a very long entry burn, though.

Coming down in a mountainous region is going to be REALLY tricky.

Deploying legs early to help me slow down, even though again this is NOT SpaceX kosher.

Missed most of the landing burn, but here's the very last bit.

A good deal of hovering and translation here to find a flat enough landing spot.

Yikes!

....but I made it, didn't I.

Now to see what happened to the upper stage!

Hah! Still in the atmosphere, but with an exoatmospheric apoapsis.

I'll go ahead and blow the fairing, though there's not much to see on the dark side.

Should be a piece of cake from here on out. Getting ready to circularize.

Stable orbit achieved!

There she is! Roadster perched atop the upper stage.

Now for the exit burn.

POW. Five gees is a bit much for the real-life Tesla, but autostrut is our friend here.

Pushing out of the system.

And there we go! Hohmann transfer above Dunian orbit!

Finally, the money shot.

"Can you hear me, Major Tom? Can you hear me, Major Tom?"

"Though I'm past one hundred thousand miles
"I'm feeling very still
"And I think my spaceship knows which way to go"

[NSEP]

Thats a big gallery of pics!

I might try this!

[sevenperforce]

4 minutes ago, NSEP said:

Thats a big gallery of pics!

I might try this!

I never can get Imgur to order my pictures the way I want, so I usually create a separate thread and paste in using postimg.

I'd love to see your entry!

[NSEP]

34 minutes ago, sevenperforce said:

I never can get Imgur to order my pictures the way I want, so I usually create a separate thread and paste in using postimg.

You can also use spoilers. Just click the eye button when writing a post and you got a spoiler that you can click to show everything 

[Geschosskopf]

Great KSP skills getting all the boosters back.  No denying that.

[DAL59]

You recovered not just one booster, but three?!  And without FMRS?!?!  

Have some rep!

Why weren't the boosters deleted because they were in the atmosphere?

[sevenperforce]

30 minutes ago, DAL59 said:

You recovered not just one booster, but three?!  And without FMRS?!?!  

Have some rep!

Why weren't the boosters deleted because they were in the atmosphere?

Hah, thanks!

Would FMRS even work for this? Seems like it would be essentially the same as a quicksaving, landing, then quickloading and landing the other, ad infinitum.

The trick was really careful timing. As far as I can tell, ships delete/unload once their apoapsis drops below 70 km. So the boosters can be in atmosphere but still be accessible as long as they are still on a suborbital spaceflight trajectory, even if they are on the downward leg of that suborbital trajectory. Of course, there's another twist: if you're controlling a ship in-atmo, it won't let you switch to another ship unless it's less than 2.5 km away. So I had to set it up so that "jumps" between vehicles only occurred when the ships were less than 2.5 km apart or when the starting vehicle was fully exoatmospheric.

Right after separation, the core was still less than 2.5 km from the first booster, so I could switch back to it for the first boostback easily enough. However, by the time I completed that boostback burn, I was more than 2.5 km from the second booster, so I had to wait until I crested out of the atmosphere before I could switch over to it for the second boostback burn. Of course, by that time, the core was well out of the atmosphere (no trouble there), but the first booster was well-into the atmosphere; I think I caught it just seconds before its apoapsis would have dropped below 70 km.

By the time I landed it, the second booster was even lower in the atmosphere, but thankfully it started with a loft so its apoapsis was still in space. Rinse and repeat.

I wasn't sure it could be done (I originally thought that perhaps I'd need to keep all of them out of the atmosphere the whole time, which would have been REALLY messy) but I'm glad I could!

[Geschosskopf]

5 minutes ago, sevenperforce said:

The trick was really careful timing

Hahah, that's pretty much the case with everything in life