Is this the max dV ( or so) that can i achieve with this vessel?

[Daze]

[RainDreamer]

Well, you do have a lot of mass. Those giant tanks still weigh a friggin lot when dry.

[Daze]

Mhm, how do you think i can improve that design? I wish to make a spaceship similar to the Nautilus-X with about 15k of dV..

[sdj64]

With that much fuel, you're pretty close to the max dV in a single stage. But, you could make it better by using the 2.5m tanks since those have a better full/empty mass ratio than the Kerbodyne ones. Also, if you're not opposed to a staged setup, put your outer tanks on decouplers and stage them off when empty. Or make the payload lighter.

[Tex_NL]

Ion engines!

But you will have to remember one thing: You'll need a lot of patience going anywhere with ions. And patience always runs out when you need it most.

[RainDreamer]

Do you intend to eject the empty tanks away once you are done with them? Noticed the docking ports. Might try an asparagus-esque fuel lines set up, and eject away the empty tanks in a way that doesn't throw off your COM, which should shed away some mass in flight and let the remaining fuel haul less mass. But that wouldn't do much still.

Need to leave behind more payload mass and increase more fuel mass.

Or, if you truly doesn't care about speed, use ion engines. It would take soooo long, but it can give you the amount of dV you need.

[Daze]

The ideal for me is to make a single stage ship, without decoupling nothing... But as i can see it's pretty impossible, so in the end i've to try with lower payload or a LOOOOOT of ion right?

[Empiro]

You can definitely get more delta-V if you're willing to deal with very long burns and very low TWR. The specific impulse of nuclear engines is 800s, you'd need a wet-to-dry ratio of about 4.5 to 1 to get 12000 m/s dV.

[Daze]

Mhm, and if i stay with the 7-8k of dV, i can go for example on Laythe + other planet (example Eeloo) than back? It'a all a fact of correct phase angle?

[cantab]

The absolute upper limit for a single nuclear-engined stage is just over 17 km/s. For an ion-engined stage it's just over 36 km/s, the greater specific impulse being partly undone by the poor mass fractions of the xenon tanks. But diminishing returns really kick in on either.

Anyway, general advice:

Don't use Kerbodyne tanks except on very large ships. They have an inferior mass fraction.

Reduce payload mass. Consider building a "pilot" craft that just carries a few Kerbals. Shave off unnecessary bits like structural parts unless you really want them.

If using ion engines, consider modded or tweakscaled tanks to keep the part count tolerable, especially on a larger ship.

Be wary of going too low on the TWR. 17 km/s means little if you can't reasonably use it. Low TWR effectively wastes delta-V too.

Finally, expect to need a LOT of fuel.

[Daze]

Mhm, i wish to make EASY mission on Jool/Eeloo, what dV do you think i need? (With a big margin of error)

[Signo]

What will you bring?

[Daze]

1-2 lander, i HOPE less than 20 ton together

[Daze]

I've made a test with a prototype, 7k dV in LKO. Nice

[Daze]

Up please

/10chars

[John FX]

I find that you can get about 7KDv with an orange tank and a NERVA. Moving up to a large kerbodyne only gets another 500-1000Dv. To get much more than that you either need silly amounts of fuel per engine (Very long burn times) or to drop tanks on the way.

[Daze]

Mhm and with about 9km dV i can go pretty much everywhere?

[panzer1b]

Mhm and with about 9km dV i can go pretty much everywhere?

I believe you can go to anywhere and get in orbit around it with 5-6K dV (i have a 5k dV fighter that can make it to every spot in teh solar system if you dont consider landing there important, nor care about returning to kerbin without a refuel). With careful planning and around 9K dV i BELIEVE you should be able to get anwyhere and return from there back to kerbin, but if you plan to land anywhere, you might need as much as 20kdV (eve prolly even more), so again, think anout what u want to do, getting to orbit around a planet and perhaps landing is rather easy, but if you want to start doing full return trips with landing and also correct for inefficient burns, you need at a bare minimum 10k dV, if not more for the farther planets (counting some screw ups here and there 20k dV should be overkill, but u wont get that outside of ion).

dV is starting to become my biggest concern right now with my newest designs, and since im fairy dead set on SSTO space planes, getting more then 10k dV is basically impossible not counting ions (which im not anywhere near patient enough to use). If i can get a 10k dV craft soon, i guesws ill have to settle for droptanks/refueling after LKO.

Edited December 12, 2014 by panzer1b

[cantab]

To make a direct Hohman transfer between Low Kerbin Orbit and Low [Target] Orbit, then back again, the most demanding target is Moho. 8 km/s should suffice at any window, though Moho does have a reputation for requiring more delta-V than you expect.

[Daze]

And for Jool(Laythe) and Eeloo it should be enough right?