NERV -- Proper Use

[IntegratingDerivatives]

I'm trying to begin learning how to deal with interplanetary missions, but I can't seem to get the hang of properly using the NERV. It's the obvious choice for interplanetary in terms of efficiency, but with the burn times so stupidly long, I can't make a craft work in a single burn. Any tips on how I could use the engine more efficiently?

[AHHans]

Welcome to the Forums.

Two tips come to my mind: one is to split up your burn: e.g. when transferring from LKO to another planet first plot a maneuver node for the transfer (so that you get the position on your orbit mostly right), then reduce the burn for that maneuver so that you stay in Kerbins SOI (e.g. up to about the Mun's orbit but without encountering the Mun), do that burn, and then do the transfer burn from that elliptical orbit (the maneuver node should be close to the PE of that orbit).

The second tip is that you can activate physics warp while firing your engines: on PC with <right-shift> - <.> (i.e. like "normal" time warp but with <right-shift> pressed). That will reduce the amount of playtime that you need for such a burn.

Another comment: my personal rule is to not have a craft with a TWR in LKO less than 0.2 (i.e. a craft with less than 0.2 g acceleration). That is just too painful. (And too long burns become inefficient.)

[Streetwind]

Welcome to the forums

If it doesn't work in a single burn, then split the burn. This is sometimes also referred to as "periapsis kicking". First, start with a partial burn of a reasonable length - no more than a fifth of a full orbit, ideally more like an eigth. Now you have a periapsis in the place where you executed your burn. Loop around the orbit once. As you pass periapsis, make a second burn. Loop around. Make a third burn. And so on. How many you need entirely depends on your spacecraft, its current location, and where you want to go.

There are various ways to improve that strategy, for example using maneuver nodes of fixed, pre-set magnitudes, or precalculating the alignment your apoapsis (unfortunately the guide for that lost all of its images).

Of course, if you really don't like long burns, you can fly with high-powered bipropellant engines instead. All planets in stock KSP can be reached effortlessly with normal chemical rocket engines. The nuclear motors and ion engines are just options which lower the launch mass, and thus likely the price, of the spacecraft. If you are playing Science or Sandbox modes, or if your Career game has no problems with paying for and launching gigantic things, then you could go to Moho or Eeloo entirely on solid rocket boosters. People have done stuff like that before.

[Spricigo]

9 hours ago, IntegratingDerivatives said:

... NERV. It's the obvious choice for interplanetary in terms of efficiency, but... 

... It's not the only choice. Pick what works best for the mission at hand. 

It happens so many times: People pick some "best something" and when the drawbacks become apparent they try to fix it and get caught in loop of improving A, then B when it affects each other negatively. 

In the case at hand, people tend to add more engines to improve TWR, but since dry mass decrease Delta-V they add more fuel to compensate, lowering TWR again. 

If your interplanetary ship can have enough Delta-V and a reasonable TWR with a single chemical engine just go for it. NERVs are awesome if you can endure the long burns. 

[magnemoe]

You can always spam them. 

Interplanetary passenger ship with room for 14 kerbals and has an large 3 man lab.
5600 m/s dV. 

its topping up its tanks in Minmus orbit. The tanker with 3 large MK3 tanks and extra resource tanks has 6 nervs and 4 thuds to help with takeoff, it don't need much trust as its just leave minus, aerobrake and match orbit with spacestation, going back to minmus its just have a bit fuel to get back and land. 

You can go overboard; I did on the passenger ship but it has enough dV