Low orbit supply delivery

[Entroper]

Design a ship to efficiently put a large payload into a stable orbit around Kerbin, stable meaning a perigee of at least 70 km. Bonus points if it\'s a nice round orbit, and the more mass you can lift, the better your design.

I\'m really just interested in seeing what kind of lift vehicle designs people can come up with, but we can make this a proper challenge with points, so here are the rules:

Your score is determined by the amount of useful cargo you can deliver to a stable orbit, and the cost of putting it there and returning your Kerbals safely to Kerbin. For the purposes of this challenge, any fuel is considered useful cargo. This includes liquid fuel tanks, RCS fuel tanks, and yes, SRBs (we\'ll pretend it\'s some other kind of storage container).

In order to score any points:

• 
  [li]You must return all three Kerbals safely to the surface of Kerbin. They can be in the ocean, they can be on land halfway around the planet from the space center, whatever, as long as they touchdown safely.[/li]
  [li]You must jettison a separate cargo stage full of unspent fuel to an orbit with a periapsis of at least 70 000 m. No rocket engines may be attached to this stage. You can attach RCS engines and fins to this stage, but their mass will not contribute to your score, and any partially-used RCS fuel tanks will count as zero.[/li]
  [li]The cargo must be delivered as one unit; it can\'t be separate pieces drifting apart. If you have multiple pieces, count only the largest single piece.[/li]
  

Scoring:

[list type=decimal]

[li]Your score is the mass of useful cargo delivered, divided by the cost to place it into orbit, minus your eccentricity factor.[/li]

[li]The mass of useful cargo is simply the total mass of all liquid fuel tanks, RCS fuel tanks, and SRBs included in the cargo stage. Any other parts in the cargo stage, such as decouplers, struts, fins, etc., do not contribute to this mass. Any fuel tanks that are not 100% full count as zero. One mass unit = one million points.[/li]

[li]Your cost is the total cost of all ship parts, minus the cost of the useful cargo parts (your clients paid for those). Include any parts used in the cargo stage that are not fuel tanks or SRBs.[/li]

[li]Your eccentricity factor is your apoapsis altitude minus your periapsis altitude, in kilometers, just prior to jettisoning the cargo. Rounder orbits are better. The altitude of your orbit does not matter for scoring, as long as your periapsis is 70 000 m or greater.[/li]

[li]Final score = cargo mass / cost - eccentricity factor[/li]

The rest of the album is here: http://imgur.com/a/ic4jL And the ship design is attached.

This ship is designed to deploy 21 full liquid fuel tanks to a 75x75 km orbit (I managed an apokerb of 76.4 km and a perikerb of 73.9 km on this run, with enough fuel to adjust if I felt like taking the time).

Launch stage is 12 SRBs, 12 LFEs, and 7 vectoring LFEs. The SRBs come off after 25 seconds, and another set of 12 SRBs ignites. Those are discarded at 50 seconds. Meanwhile, the outer 12 LFE stacks are pumping fuel to the vectoring LFE stacks. After just over 2 minutes, these outer liquid boosters are discarded for the final leg of the trip. The remaining 7 vectoring LFEs perform the final orbital insertion. Then you just separate the payload and pilot the capsule back home.

Unfortunately, there\'s a quirk to this design, which is that the payload is actually delivered empty, while the orbital insertion stage is jettisoned full. You can see this in one of the screenshots, there is enough fuel for the payload to be full, the fuel is just in the wrong tanks! Oh, dear. The problem, of course, is that the stack decoupler allows fuel to pass through it, which in this case, is not a feature that we want on this ship. Oh well. I wanted to do it using stock parts, but maybe I\'ll just disable fuel pass-through for the decoupler and give it another try.

I could also make the return stage much smaller; a simple RCS stack would be lighter and more than enough to get home, and it would also allow for adjusting the orbit of the payload before dropping it off.

[Kosmo-not]

I think this needs to go in the spacecraft exchange forum.

[Spacecats!]

I think this needs to go in the spacecraft exchange forum.

Yes, either it needs to move or a challenge needs to be stated.

[Entroper]

I\'ve edited the post to state an official challenge. I really just wanted to see what kind of lift vehicles people can come up with, but this is fun too.

[Warringer]

Perfect start for lifting fuel for larger missions into deep space once persistence and other stellar objects are there...

[Entroper]

Perfect start for lifting fuel for larger missions into deep space once persistence and other stellar objects are there...

Exactly. Or you could consider the tanks to be filled with LOX or other supplies for a low-orbit space station, or components, or whatever.

[Entroper]

I solved the 'wrong tanks' problem by realizing that fuel won\'t flow through an SRB. So just put an SRB near the bottom of your cargo stack, and you\'re set. Gearing up for my first scored attempt now.

[Entroper]

My first real attempt (video is still processing, be patient):

I succeeded in putting a cargo stage of 20 liquid fuel tanks and 1 SRB into orbit. 1 000 000 * (20*2.5 + 1*1.8) = 51 800 000 points.

Cost:

12 SRBs on radial decouplers

12 stacks of 3xLFT, 1xLFE, on radial decouplers

12 struts and 12 fuel pumps

7 stacks of 3xLFT, 1xLFE(vectoring), 6 radial decouplers, 6 struts at the base, 6 more to support the cargo

2 stack decouplers, one before and one after the cargo

1xLFT, 1xLFE, 1x stack decoupler, 1xPod, 1xChute

12*450 + 58*550 + 13*850 + 30*1275 + 24*250 + 12*250 + 7*950 + 3*975 + 1600 + 422 = 107 197 points

Ap = 88 750 m, Pe = 70 041, eccentricity penalty = 18.709 points

51 800 000 / 107 197 - 18.709 = 464.5 points

[LambdaCactus]

Good job! Looks like you still had enough fuel there to circularize your orbit if you waited until reaching Apo before dumping the lifter stage. Also, you should be able to lighten your orbiter by just using RCS to deorbit instead of wasting mass on a whole engine and a nearly-full tank.

[Entroper]

Good job! Looks like you still had enough fuel there to circularize your orbit if you waited until reaching Apo before dumping the lifter stage. Also, you should be able to lighten your orbiter by just using RCS to deorbit instead of wasting mass on a whole engine and a nearly-full tank.

Yeah, at one point you can see me pivoting the ship and checking the map, but I decided I was too far from Ap to bother waiting, and too far from Pe to do much of a correction. You can see me make a small correction burn before throwing away the engines, trimming the Ap as much as I could without putting the Pe below 70 km. It\'s for this reason I usually aim for 150 km in other challenges, so I can time warp faster. But I probably didn\'t have enough fuel to go that high. I was surprised how 'close to the margin' this design ended up.

I considered going the RCS route, but determined that the cost factor would actually be higher, even if I only used a pair of RCS blocks. Since the mass of the final stage is fairly small relative to the rest of the ship, I decided not to bother with it. I\'m going to try another design or two tonight, based on the fact that radial decouplers are ghastly expensive. When the game gets closer to completion and has normal objectives, these kinds of challenges should get more interesting, because I expect they\'ll rebalance the costs of the parts.

[Entroper]

OK, removed all the SRBs from the boost stage, and added a ring of 12 fuel tanks supporting the liquid boosters. That subtracts 12*(450 + 1275) and adds 12*550 to the cost. And I achieved Pe = 73.2 km, Ap = 74.5 km this time.

51 800 000 / 93 097 - 1.3 = 555.1 points Woohoo!

[Entroper]

Added some cargo weight. 6 more SRBs, but I changed 6 of the LFTs to SRBs.

58 400 000 / 93 097 - 8.4 = 618.9 points

[Thomas_Jefferson]

First successful cargo drop.

Total cargo delivered: 5 Fuel Drums = 12500000

Total cost:4 fins,6 struts,5 engines,25 fuel, 2 decoupler, parachute, booster, Command module, Advaced SAS = 28222

efficiency = 309-303 = 6

Total score = 436.9

seperation didn\'t go as planned but it is within the rules.

This is the whole rocket.

[Entroper]

Nice! Simple and straightforward often beats complex. I bet that design would lift a bit more weight, since you got to a nice high orbit.

[Thomas_Jefferson]

Second successful cargo drop.

Total cargo delivered: 7 Fuel Drums = 17500000

Total cost:2 fins,4 struts,9 engines,35 fuel, 2 decoupler, parachute, booster, Command module, Advaced SAS = 35622

efficiency = 137-136 = 1

Total score = 490.2

I used the cargo as a separate stage. Is that against the rules?

[Entroper]

I decided to try to reach the Mun with my ship. I reconfigured the cargo to 7 SRBs and 7 LFTs and made it to a 25.0 x 25.6 km orbit around the Mun. Not bad! It looks like it\'s going to take an awful lot to make Mun deliveries of any significant size. My payload was only 30.1 units. 322.7 points for a delivery to the Mun.

This is actually good to know. The same ship that delivered 58.4 units to low Kerbin orbit delivered 30.1 units to low Munar orbit, with just a tad more to spare. So whatever you can deliver to low Kerbin orbit, you can deliver just over half that to the Mun.

[RayneCloud]

Once full persistence comes out and we actually get space-stations down the road, being able to put fuel in orbit for orbital refueling will be pretty epic. Good job on this challenge and the ship Entroper.

[Entroper]

Once full persistence comes out and we actually get space-stations down the road, being able to put fuel in orbit for orbital refueling will be pretty epic. Good job on this challenge and the ship Entroper.

Yeah, I\'m really looking forward to docking. I think it\'ll enable some really interesting designs.

[Thomas_Jefferson]

The milk has been delivered. the bottom of the rocket did not detach again.

cost of 22232

efficiency 10

drop off bonus 7500000

total scoree: 327

[Thomas_Jefferson]

Another delivery done.

cost of 58322

efficiency of 3

delivery bonus of 32500000

total score: 554

[Entroper]

Now that\'s creative looking. I like it, it looks easier to attach more or fewer tanks.