Interplanetary heavy payloads

[RonnieThePotato]

So anyone know a good way to send heavy payloads interplanetary? I would like to send a big submarine to laythe. The submarine is < 20 tons. Anyone know a good way to carry this all the way to laythe?

 

[Streetwind]

Moar Boosters.

 

 

...What? No seriously, that's a valid answer here!

 

 

...Okay, okay! So, what you need is an understanding of mass fractions, AKA the fueled mass divided by the empty mass. Since you have a giant payload, which equals a lot of empty mass, you also need a lot of fuel in order to get a good mass fraction. This is important, because the mass fraction is what determines your dV.

So in order to lug that submarine to Jool, you will need a transfer stage large enough to provide that mass fraction, and thereby, the dV. And in order to launch the submarine and the required transfer stage from Kerbin, you will need a giant rocket.

In other words, you need moar boosters. Q.E.D.

Edited July 25, 2016 by Streetwind

[Aegolius13]

Nuclear engines are probably your best choice for a large interplanetary load. You may need several to get an acceptable TWR, but since they're heavy, the fewer you can use, the better your delta v will be.

You can save a lot of fuel on the capture by either doing a gravity assist around one of the Joolian moons (Tylo is my favorite), and/or aerobraking at Laythe.  But you might need a heat shield for the latter.

[Snark]

Yes, a big "interplanetary booster" with LV-N engines is likely your best bet.  If you're not used to using them, bear in mind that they run on liquid fuel only (no oxidizer), so don't use the usual LFO tanks for rockets; use LF-only tanks, such as (for a big ship) the Mk3 liquid-fuel fuselages.

You could make the LV-N transfer stage part of one giant launch that includes your submarine; or you could have it be a separate "tug" ship that you launch separately, and dock with the submarine prior to departure.

Definitely use a reverse gravity assist upon arrival at Jool, using either Tylo or Laythe.  It will save lots of dV.

Aerobraking at Laythe will also save a lot of fuel.  For a big 20+ ton ship, I highly recommend the inflatable 10m heatshield, it does wonders.  Extremely effective at its job, and is so big when inflated that it easily protects even very bulky ships.

[RonnieThePotato]

I figured it out, I completely forgot about docking. I sent the payload into Kerbin orbit and simply docked the transfer stage right behind by submarine. I used both of your aerobraking tips and made it to lathe with ~150 dV to spare, thanks for the help!