Challenge: Reusability Extreme

Cosmo's fan · Jun 21, 2020

Hey, you know what,
Done!
Build menu-

On pad-

Liftoff-

Ascent-

First stage sep-

Leo-

First stage recovered-

Using moon's gravity,moon fly by

-

Orbit after slingshot-

Adjusted orbit to get an encounter with mars-

Mars fly by trajectory(actually not a fly by)-

Aerobraking at arrival-

Mars orbit insertion-

Parachute deployed-

Landed on mars-

Mars orbit insertion-

Tranfer orbit to earth-

Cosmo's fan · Jun 21, 2020

Reenty-

Parachute deployment-

Landed back safely on earth-

Part count:-

Fuel tanks-5
Engines-2
Chutes-7
Dock port-1
Probe or capsule-2

Total parts:-17

Pink · Jun 21, 2020

I like it!

Altaïr · Jun 21, 2020

Very good one, but be careful, the gravity assist with the Moon is actually counter-productive. You'll need more fuel to correct your trajectory than what you would have needed for a direct injection burn.

Still, well done

Cosmo's fan · Jun 21, 2020

Altaïr said:

Tried like 16 times and it was very helpful there

TtTOtW · Jun 21, 2020

Cosmo's fan said:

Yeah it is occasionally quite the help

phantom · Jun 23, 2020

Just like the KSP Reddit challenges.

Edspace Agency · Jun 24, 2020

Anton Roche said:

That rocket was here on forum

Roger Jolly · Jun 24, 2020

Aww...epic fail

16 part rocket,
The Moonenator SSTM&R with Lander

Left the travel rocket in wide orbit to save fuel

Landed fine but forgot to leave some rendezvous fuel in the rocket with the RCSs

But, those powerful port magnets save the day!

But shit...that fuel gauge

WTF!!!

phantom · Jun 25, 2020

Roger Jolly said:

Aww...epic fail
View attachment 40374 16 part rocket,
The Moonenator SSTM&R with Lander View attachment 40376 Left the travel rocket in wide orbit to save fuel View attachment 40369 Landed fine but forgot to leave some rendezvous fuel in the rocket with the RCSs View attachment 40370 But, those powerful port magnets save the day! View attachment 40372 But shit...that fuel gauge View attachment 40371 View attachment 40373 WTF!!!

Been there, once did a Venus ascent and I had 0.1% fuel less than the required.

Cosmo's fan · Jun 25, 2020

phantom said:

Try with a valiant on lander and remove kolibri from the first stage

Cosmo's fan · Jun 25, 2020

Shift some fuel from first stage to lander, if you are using a valiant there

Roger Jolly · Jun 25, 2020

Cosmo's fan said:

It was rather a surprising success for a second flight I didn’t expect, I’d have just made it with a better rendezvous but for this new system bewildering me

Not sure if removing any kohlrabi would work but I’ll try, I could definitely remove the rcs and make the lander 1 part fuel for 13 parts, maybe find some funky sideways balance so I can have only one engine on the lander or make it upside down and probably going to need two chutes

Chillum · Jun 26, 2020

To be fully reusable, surely it should be required that it must be possible to refuel the vehicle, and possible to replace any parachutes that are used?

Pink · Jun 26, 2020

Chillum said:

If I understand correctly, he used 'reuseable' when he meant 'recoverable'. All the parts of the rocket have to land on Earth with no broken parts.

Blazer Ayanami · Jun 26, 2020

Chillum said:

Precisely. Recover, reassemble, refuel, relaunch. That's what real reusability is.

Horus Lupercal · Jun 29, 2020

Anton Roche said:

Video is finally ready.

A Disclaimer.
Firstly: My rocket actually has 21 parts.
There is a probe core buried on the first stage which I forgot about after testing before the mission started and only noticed it during video editing. It makes no difference to the job really since I never control the first stage once the upper section is separated. But if anyone is going to get excited about it I'm more than happy to re-do the mission minus the 2.5tons of dead weight on board to prove a point.
Secondly: I done it in 1.4, not 1.5. Why? Cos I'm not done with 1.4.06, that's why. And before someone starts whining about the different solar system sizes and it's easier in 1.4, I'm going to say 'check the Dv map'. The actual budget from LEO to the moon is almost the same, give or take a few m/s (821‬m/s to 829m/s). Same with to Mars (1,154m/s to 1,205‬m/s. Now balance that against me using a broken drag system (I'm not sure what the 1.5 LEO figure is, but I'll put money it isn't even close to 3500+m/s...) and less efficient engines and tell me it's easier. And yeah, drag is properly on. I start at the menu screen and you can tell it's on cos I'm not supersonic until 10km up.

The tale then.
If you're gonna do re-usable, then you need to actually re-use the rocket.
It's something that gets said a lot, but how many of you actually re-service your launch systems in-game? I suspect not as many as there are 're-usable' rockets around, that's for damn sure. And this is supposed to be a SpaceX company mission goal, fully re-usable, rapid turn around rockets. The idea is they want to be able to launch, land, top up the tanks, bang a new payload onboard and send it straight back up.
So that is pretty much what I was going to do, even if the challenge itself was quite...restrained...in its aims.

Looking at the challenge criteria, 20 parts sounds like it's supposed to be some kind of smart limitation on size whilst totally forgetting that even 5 fuel tanks is nearly 450 tons of mass in 1.4, and in 1.5, it's even more (600tons). So fuel mass / Dv was never going to be an issue.
What it did do though was limit toys you could bring along to facilitate that 're-usability'. Docking ports, staging, parachutes, engines, landing legs etc.
Because of that, this required a simple but not light approach, which is why I went with an SSTO style design for the first part.
Then, the lander itself. The smaller I could make it the better, so a grasshopper, enough fuel to do powered landing and take-offs with landing legs on the side. And then an orbital re-fuel tank that it'd push around the solar system, leave in orbit, land, launch, RV with, dock and then push back. This approach lowered the overall mass considerably, keeping the SSTO launch mass down.
I also decided that RCS is too mainstream and went with main engine docking manoeuvres. Cos I can. This has the advantage of not only further reducing part count, dry weight and aerodynamics, but also fuel if you know what you're doing.

Kerb weight is about 300tons, maybe less. I could've got it to about 200 with a 2 stage launch system, but that pushed me over the parts threshold (ironically) and wasn't viable.

Then it was a simple case of putting legs under it, building a re-fuel truck for it, testing to see if it can be landed, connected to the truck and then re-launched before starting the mission.

It's fucking ugly though, and I've got a beautiful Uranus IB set up with a much better looking truck as well in-case I get bored and want to do the mission again.

The mission itself goes as thus:

Spawn on the pad and blast into a very low orbit with the SSTO.
De-couple the Lander and fuel tank, burn TLI to the moon.
Rather than bring everything down to LLO, to save fuel I circularised to a rather eccentric orbit facing back out towards Earth.
Left the fuel tank upstairs and powered landing to the surface and blast straight back to another low (350m ish) orbit.
Grab an encounter (with a 200m/s speed difference), dock (without RCS) and then TEI back to Earth
Aerobrake, make an encounter with the SSTO still sitting empty in LEO, dock (after cancelling out the enormous orbital speed difference)
Transfer the remaining fuel to the SSTO
De-orbit
Powered landing onto the Launchpad
Mission One complete
Re-fuel SSTO from fuel truck.
Launch to LEO again
Decouple and burn TMI to Mars aerobrake
Again, no point bringing the fuel tank all the way down so aerobrake until the orbit is facing back out towards Earth, raise the periapsis until it's above Mars atmosphere
De-orbit, parachute landing and straight back up to LMO
Encounter and dock with the fuel tank
Burn out of the SOI and lower the perihelion to Earths level
Get a decently close approach and adjust with deep space burns to encounter
Aerobrake
Set up docking encounter with SSTO in LEO
Dock with SSTO and transfer fuel (if you look closely enough, my encounter orbit puts me at 28.5km periapsis and have to do some adjusting on the fly cos I can't go around again. I make the dock at 30.4km...
Pre-landing fuel transfer and de-orbit burn
Powered landing at the launchpad
End of Mission Two
Re-fuel SSTO from truck and launch back to LEO.

Rinse and repeat.

As Steve puts it,

If I'm honest, making the video was harder than the challenge itself. Condensing over an hour of silent footage into an 11 minute video with added and properly timed sound effects took ages. But I'm pretty happy with both, especially as it's the return of the NoPro brand hehe.

Cosmo's fan · Jun 29, 2020

Nicely done!

Mars Pathfinder · Jun 29, 2020

Blazer said:

i remembered space shuttle :3
thou failed to lower the launch cost....

smol · Jul 5, 2020

Optimizing for parts count instead of weight was an interesting twist to my smol rocket enterprises. My first attempt was a two stage rocket, with the second stage getting from (almost) LEO to lunar surface and back to earth. Plan was to have a spent stage 1 not quite make it to LEO, and land gently on a couple of parachutes. Ho hum, here's the printout, picture, and part count.

I'm going to dispense with all the photos of the mission. It was easy to fly, and the mission was unremarkable. If you want to build it, fly it, post the pictures, and take all the credit, I don't care. It works.

Code:

Stage nearLEO-LLO-Moon-LLO-Earth Report:
  Bill Of Materials
    1 x parachute
    1 x probe
    1 x Kolibri engines
    10.0 tons of fuel tank
  thrust=15.0T; TWR(earth)=1.08 (>=0.17); burn time=156s (>=116)
  total weight 13.90 tons; deltaV=2657m/s (>=1666)

Stage Earth-nearLEO Report:
  Bill Of Materials
    2 x parachute
    1 x (13.90T stage LEO-LLO-Moon-LLO-Earth)
    1 x probe
    1 x separator-4w
    1 x Frontier engines
    40.0 tons of fuel tank
  thrust=100.0T; TWR(earth)=1.56 (>=1.20); burn time=104s (>=94)
  total weight 64.10 tons; deltaV=2344m/s (>=2009)

Part count 11. Maybe could have gotten part count down to 10 by replacing the two 20T tanks with an 8-wide 40T tank (with a subsequent loss in aerodynamics). Whatever. Left as an exercise to the reader, etc. This rocket does not bring me joy.

Continued...

smol · Jul 5, 2020

The game gets interesting when (as Horus already discovered) you lower the part count by designing the entire mission in one stage. I have no earthly idea why our customer wants to optimize part count (maybe they don't have amazon prime and have to pay significant shipping costs per part?!?), but that's the contract and I'm in it to win it.

In theory, you can overcome the restrictions of sufficient TWR to leave earth, and the delta-V of earth-moon-earth capture with this vessel:

Code:

Stage SS-Apollo-1F Report:
  Bill Of Materials
    1 x probe
    1 x parachute
    1 x Frontier engines
    80.0 tons of fuel tank
  thrust=100.0T; TWR(earth)=1.12 (>=1.10); burn time=209s (>=207)
  total weight 89.40 tons; deltaV=4651m/s (>=4566)

Part count = 4 (use an 8wide 80T tank, mount the probe sideways)

Or even this vessel:

Code:

Stage SS-Apollo-2F Report:
  Bill Of Materials
    1 x probe
    1 x parachute
    2 x Frontier engines
    145.0 tons of fuel tank
  thrust=200.0T; TWR(earth)=1.25 (>=1.20); burn time=189s (>=189)
  total weight 160.40 tons; deltaV=4774m/s (>=4766)

Part count=6 (use a 12w 120T base tank, and then on top of it place a 8w 40T tank, for a total of 145T of tank, mount the probe sideways)

In theory, theory works the same as practice. In practice, it usually doesn't. I tried flying these rockets. Multiple times. The numbers don't lie, and they are right there in the printout. Either one SHOULD be able to fly to the moon and back, but I just couldn't. This is likely due to the combination of my rookie piloting skillz, and the complete snitshow of trying to land a 40T (+fumes) rocket in lunar gravity WITH TWO FRONTIERS. Talk about a jumpy throttle!! If a better pilot than me can fly one of my rockets to the moon and back, you win the prize. I would have mad respect, and maybe we could form a partnership.

This bring us to my entry in the contest. If we go one more and try a three engine solution, behold my masterpiece:

Code:

Stage SS-Apollo-3F Report:
  Bill Of Materials
    1 x probe
    1 x parachute
    3 x Frontier engines
    220.0 tons of fuel tank
  thrust=300.0T; TWR(earth)=1.24 (>=1.20); burn time=191s (>=191)
  total weight 241.40 tons; deltaV=4877m/s (>=4866)

Part count=7. The trapezoid is an 8w 80T tank.

I only used one engine for lunar descent / ascent and the injections. And boy did I use every piloting skill in the book:

- Optimizing the earth ascent angles (lots of trial and error) to get LEO with 23% in the tank and an altitude of as close to 30km as I could get.

- Time warping so the Trans-lunar injection started at my earth periapsis.

- Bleeding off all horizontal lunar velocity and then suicide burn vertical lunar landing (6.1% fuel on lunar surface).

- Launching from the moon straight up to 5000m at maximum thrust (no atmosphere, so why not?) and then gently gently making lunar orbit at 5000m (fuel 1.9% at LLO). With three frontiers (300T thrust) and a tank on fumes, let's say the vertical portion of the maneuver didn't take ver long.

- Time warping until the Trans-earth Injection was also at lunar periapsis. (Fuel 0.6% to his earth atmosphere)

- Launching my parachute as close to 2500m, and figuring out the optimum throttle to start a suicide burn at 100m (25% I think). My reflexes aren't fast enough to start the burn later than that.

Results:

ZERO POINT ONE PERCENT FUEL REMAINING!!!

There you have it. 7 parts to the moon and back. Can somebody beat me with either my 6 part or 4 part designs?

Pink · Jul 5, 2020

smol said:

The game gets interesting when (as Horus already discovered) you lower the part count by designing the entire mission in one stage. I have no earthly idea why our customer wants to optimize part count (maybe they don't have amazon prime and have to pay significant shipping costs per part?!?), but that's the contract and I'm in it to win it.

In theory, you can overcome the restrictions of sufficient TWR to leave earth, and the delta-V of earth-moon-earth capture with this vessel:

Code:

Stage SS-Apollo-1F Report:
  Bill Of Materials
    1 x probe
    1 x parachute
    1 x Frontier engines
    80.0 tons of fuel tank
  thrust=100.0T; TWR(earth)=1.12 (>=1.10); burn time=209s (>=207)
  total weight 89.40 tons; deltaV=4651m/s (>=4566)

Part count = 4 (use an 8wide 80T tank, mount the probe sideways)

Or even this vessel:

Code:

Stage SS-Apollo-2F Report:
  Bill Of Materials
    1 x probe
    1 x parachute
    2 x Frontier engines
    145.0 tons of fuel tank
  thrust=200.0T; TWR(earth)=1.25 (>=1.20); burn time=189s (>=189)
  total weight 160.40 tons; deltaV=4774m/s (>=4766)

Part count=6 (use a 12w 120T base tank, and then on top of it place a 8w 40T tank, for a total of 145T of tank, mount the probe sideways)

In theory, theory works the same as practice. In practice, it usually doesn't. I tried flying these rockets. Multiple times. The numbers don't lie, and they are right there in the printout. Either one SHOULD be able to fly to the moon and back, but I just couldn't. This is likely due to the combination of my rookie piloting skillz, and the complete snitshow of trying to land a 40T (+fumes) rocket in lunar gravity WITH TWO FRONTIERS. Talk about a jumpy throttle!! If a better pilot than me can fly one of my rockets to the moon and back, you win the prize. I would have mad respect, and maybe we could form a partnership.

This bring us to my entry in the contest. If we go one more and try a three engine solution, behold my masterpiece:

Code:

Stage SS-Apollo-3F Report:
  Bill Of Materials
    1 x probe
    1 x parachute
    3 x Frontier engines
    220.0 tons of fuel tank
  thrust=300.0T; TWR(earth)=1.24 (>=1.20); burn time=191s (>=191)
  total weight 241.40 tons; deltaV=4877m/s (>=4866)

View attachment 41305

Part count=7. The trapezoid is an 8w 80T tank.

I only used one engine for lunar descent / ascent and the injections. And boy did I use every piloting skill in the book:

- Optimizing the earth ascent angles (lots of trial and error) to get LEO with 23% in the tank and an altitude of as close to 30km as I could get.

- Time warping so the Trans-lunar injection started at my earth periapsis.

- Bleeding off all horizontal lunar velocity and then suicide burn vertical lunar landing (6.1% fuel on lunar surface).

- Launching from the moon straight up to 5000m at maximum thrust (no atmosphere, so why not?) and then gently gently making lunar orbit at 5000m (fuel 1.9% at LLO). With three frontiers (300T thrust) and a tank on fumes, let's say the vertical portion of the maneuver didn't take ver long.

- Time warping until the Trans-earth Injection was also at lunar periapsis. (Fuel 0.6% to his earth atmosphere)

- Launching my parachute as close to 2500m, and figuring out the optimum throttle to start a suicide burn at 100m (25% I think). My reflexes aren't fast enough to start the burn later than that.

Results:

View attachment 41306

View attachment 41307

View attachment 41308

ZERO POINT ONE PERCENT FUEL REMAINING!!!

There you have it. 7 parts to the moon and back. Can somebody beat me with either my 6 part or 4 part designs?

I like your mission!

I know you like efficiency, so I have two comments in that vein:
Lighting one engine instead of three when you're in space won't increase your dV. (Unless, of course, the excess thrust makes you overshoot)
Launching straight off the moon makes you lose dV to gravity losses. The lack of atmosphere on the moon and the extra thrust at your disposal (remember the previous comment) means your rocket is ideally suited to launching off the moon at a shallow angle like this:

(Even shallower, if possible. The goal is to be parallel to the ground as fast as possible)

Horus Lupercal · Jul 5, 2020

smol said:

Apologies for the delay. Bluestacks + Mouse isn't as precise and quick to react as a touch screen is so had to do a few run ins on the suicide burn and the flight as a whole isn't as efficient as I'd have liked. And it's the first time I've been outside LEO in 1.5, so was also learning how the transfer system actually worked...

Anyway.

6 parts, 155t, landed with 1.4% left in the tanks. Do I get a cookie...?

Just to iterate what Mooncrasher has already said. Dv depends on mass, fuel and efficiency, not thrust. So all that burning one engine instead of 3 does is increase your burn time, not your Dv. Which is usually less efficient cos you're affected by gravity for a lot longer and every second is another 1.42m/s Dv wasted.
Same with the landing burns. By slowing down horizontally and then vertically, you're essentially increasing your landing Dv budget as every single second you're above ground is another 1.42m/s you have to cancel back out again.
If you watch the suicide burn from my video (and the image above), you'll see I'm screaming in very low horizontally and then adjusting my burn direction on the fly to cancel out and manage both horizontal and vertical speeds before I hit the ground. This means I'm wasting minimum amounts of time landing and thus Dv wastage due to gravity. Getting it right requires a lot of crashing practice but once you understand the principles of how to adjust your flight profile at very low levels then your landings will get much, much more efficient.

Same with lift off. 5000m is waaaay too high and a waste of fuel on an airless rock. Figure out how high the terrain is, and get as low to that as you can. Again, that kind of thing takes a lot of practice, especially with high thrust SSTOs like this, but well worth the time.
OR
Do what I did, burn straight up and fuck the orbit off as it gave me an encounter with Earth anyway and just tore straight into the atmosphere ready for the parachutes to deploy.

Also, as bit of an experiment that may interest you, I tried your 4 part rocket just for a giggle. And despite having only a little bit less Dv (4731 - 4651), cos of the lower TWR and spending more time messing around with gravity, the 6 part version cost 2721m/s to LEO and the 4 part cost 3137m/s, which is why it's suddenly not capable of a return lunar journey.
*This is with the same flight path

smol · Jul 5, 2020

I am getting some flak for reaching LLO above 5000m for the return trip. The reason I did it was because often my transfer window back to earth was far away from me, and I wanted the ability to time warp 3/4 of the way around the moon. I was too impatient to wait at 1x time.

I am also getting some flak for operating one engine instead of three. I know how ISP works, and I know it doesn’t add efficiency. The only reason I sometimes operated on one engine was for fine control... the throttle was too twitchy with three engines and I would overshoot my goals.

I am also getting flak because I was breaking up the horizontal and vertical portions of my flight. Because that is dumb and inefficient. Case closed.

Lessons learned from the above posts (and thanks all you guys, I really appreciate your advice!):

It is possible to skip the LLO stage and just fly straight home from the moon.

It is more efficient to combine the horizontal and vertical potions of orbiting / deorbiting / landing maneuvers.

Horus Lupercal · Jul 5, 2020

smol said:

Wouldn't quite call it flak dude.

smol said:

Easy fix. Have another object somewhere in the solar system (even on the launch pad) to switch to, timewarp as required and then switch back

smol said:

Throttle down...? I was working with a mouse and keyboard for these last ones (keyboard basically jumps your throttle by 40% each time you press up or down) and didn't have problems

smol said:

Just landing approach. De-orbiting you can just burn retrograde and let gravity do the downwards work for you.

Challenge: Reusability Extreme

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