Help on Designing a Rocket (WARNING: Slight wall of text below)

[Abraxas Defiant]

Hello there, I'm still fairly new into the mechanics of Kerbal space program. I have over 100 hours into the game and mostly understand these new aerodynamics, but I am having issues building a rocket that can go just about anywhere in return. My best rocket weighs 384,000 Kg roughly and has about 10.7k Delta-V. I know that I can do much better than that, because I've seen designs of rockets that way 200 Kg or less and reach upwards of 13k to 15k Delta-V. If someone would be able to help me figure out how to construct a rocket where I can get the highest possible Delta-V that weighs 200 Kg or less and doesn't have assembled in space, I would massively appreciate it! If my desires are too steep, let me know as well.

[Francois424]

With your criteria,  you best bet would be a very small probe with a single tank of Xenon Gas and Ion engine.  most likely a small battery with the minimum amount of solar panels required.
Stack the thing on top of a 4k D-V launcher ( for 100/100 circularization ) and send it up.

The craft would have very limited uses tho, as it is extremely low-weight you don't want to clog it with science experiments or Cockpit+Kerbal.

[Abraxas Defiant]

I do appreciate the response and will keep that in mind for probes, but I ask you, how would I go about building a manned spacecraft capable of landing and returning from eeloo/dres? In terms of mass, it doesn't matter to me, but efficiency is what I care about. I would like to be able to build a manned spacecraft with maximum Delta-V to go just about anywhere in the system and be able to return if possible. I don't really know too much about the advanced maneuvers such as the hohmann and others like it. Am I asking too much? Because no matter what I do I seem to only be able to push out 9-10k Delta-V on a craft that is 350,000 Kg or more and I know that I can do much better, but haven't the slightest clue how to.

EDIT #1: Okay, so I managed to create a craft that has about 10.8k Delta-V, but the weight is about 190,000 as opposed to 350k. I'm started to understand it a bit better than previous attempts.

Edited January 28, 2016 by Abraxas Defiant

[Red Iron Crown]

Moved over to Gameplay Questions.

[Snark]

Everything is a tradeoff.

For example, if what you want is the maximum dV for the lowest mass, then you need a really high Isp, which means using ion drive. If you build an ion-powered ship with many xenon droptanks, you can pack a ridiculous amount of dV into a craft of modest mass. However, its TWR will be so low that your maneuvers will take hours of burn time.

For a slightly less extreme experience, a nuke engine with plenty of LF drop tanks will do pretty well. Again, it will be a low TWR, but much better than ion drive.

[Blaarkies]

Staging is frequently underestimated. It is possible to create 10K dv crafts with just engines less efficient than the LVN-909(Terrier), by using the likes of "Reliant".

For any stage you will get the most dv per fuel mass for the first few drops of fuel...as you fill up, you need to "drag" that extra fuel and tanks along(the first few drops of a full tanks is the least efficient drop).

Anyway, what i'm getting at is:

• Build you final payload(the probe, or the Mk1 capsule ready for re-entry).
• Notice the total mass. (We will call this the final payload mass)
• Stick the lightest engine you own on there.
• For 300isp engines, you need filled fuel tanks with about twice the mass of the final payload.

Example:

• You manage to build a final payload of 2ton.
• Now you need to add 2x2 tons of filled fuel tanks
• The total mass of this last stage(stage 0 is payload, stage 1 is payload+fueltank) should be around 6t.  "2+4 ton...or 2ton(payload)x3"
• The stage below that should have the same ratio of fuel tank to payload...giving a total (stage 2) mass of 6tx3 = 18t
• ...
• profit!!!

So do this formula for efficiently sized stage.   2 x 3^4

(Payload) x [ (Tank-to-payload-ratio)^(number-of-stages) ]

For every stage, you should get nearly 3000m/s dv...for a 4 stage rocket, thats almost 12000m/s dv, on tier 3 technology!. The launch mass gets to be around 162t.

It is easy to see how the final payload mass can eat away at your dv...a barebone probe can get 12k dv from a 33t launch    ( 0.4 x 3^4 )

[Knaapie]

Uhhmm.. You're asking for a 200kg rocket.. If it needs to be lifted of Kerbin, it should be heavier than that. I'm expecting that you mean 200 tons . Or your desires are too steep ^^

Here are 2 basic ideas

fast build and admittedly not perfect. They do symbolize two ideas, using different engines.

in general: These are landers with return ability, all electricity needs are handled by 1 rtg and yes, an extra reaction wheel wouldnt hurt for turning speed, you could do w/o. No ship can land anywhere and return (unless you believe the dude on youtube who went everywhere with 1 craft ^^), these two could land on most planets. Tylo, Laythe and Eve would require redesigns. Both rockets have an "ant engine" as final stage for the final ajustments. Not needing a capsule would be a different story though.. and for Moho and Gilly, you should consider ion, if you have the patience.

nr 1, 205t: use the interplanetary stage engines, as lander engines and return engines. Only ditch used tanks when you can. (Do not carry more heavy engines than needed !! ) Its downside is aerodynamic drag during take-off. You can easily upgrage this ship by adding a liquid fuel tank in the interplanetary stage...  Did I accidentally create a Tylo lander ? ^^.. It needs the extra liquid tank and the landing/return would be too close for comfort, but nb at all.  ^^

nr 2, 266t: cheaper and lower tier poodle and lv-909 as final engine prior to the ant. This is probably considered to be a "standard" rocket design. More streamlined but heavier with less dv. The poodle stage seems a bit large, but it is a strong engine and I went for it because I dont like littering space with debris ^^. Note the use of fuel lines, giving that last mainsail a full tank at stage 6 and getting pretty close to the perfect stage mass ratios Blaarkies explains. Note that using a single nuclear engine for the interplanetary stage would lower the total mass quite a bit.

(It might not be able to lift off from Duna. It also could use a slightly heavier lifter with 200 more dv, yet it should be sufficient for most planets)

 

Edited January 29, 2016 by Knaapie
200 kg tons ?

[Knaapie]

To basically cheat your way to any place in the solar system and back again:

 

Put a command seat in a service bay and get a Kerbal seated before launch.

 

 

Edited January 30, 2016 by Knaapie
credits to Foxter for uploading an example