Maneuver nodes don't seem to be very useful for extremely long burn times (using a nuclear engine)

[Superfluous J]

I haven't even tried to set up an interplanetary maneuver node yet! I was trying to find a video in your first bases series that showed me, but I've not had time to look very hard! I think I may well fling a couple of probes first.. If atmosphere is there, then chutes work, if chutes work, unmaned crazy beagle like missions are go!

Can I put a flag on the back of my probe and hope it sticks up out of the ground after impact? (Place flag on Duna contract! lol)

Will you return to bases when version 1.0 is out?

Actually I rebooted Bases, and it's my current series. My first series I was still learning a lot (I'm even now still learning, just not a lot any more). I've only done two interplanetary ejection in that series, and I'm not sure I described them very well.

You would likely be better of watching my old

series. Every set of episodes around a planet was pretty fully documented. You're going to Duna, so I suggest you watch Ikepollo or Dunpollo to see how I did it.

[Sirrobert]

I haven't even tried to set up an interplanetary maneuver node yet! I was trying to find a video in your first bases series that showed me, but I've not had time to look very hard! I think I may well fling a couple of probes first.. If atmosphere is there, then chutes work, if chutes work, unmaned crazy beagle like missions are go!

Can I put a flag on the back of my probe and hope it sticks up out of the ground after impact? (Place flag on Duna contract! lol)

Will you return to bases when version 1.0 is out?

Remember that Duna does have a very thin atmosphere, so you'll need more parachutes to safely land than you would on Kerbin

[MoridinUK]

Actually I rebooted Bases, and it's my current series. My first series I was still learning a lot (I'm even now still learning, just not a lot any more). I've only done two interplanetary ejection in that series, and I'm not sure I described them very well.

You would likely be better of watching my old

series. Every set of episodes around a planet was pretty fully documented. You're going to Duna, so I suggest you watch Ikepollo or Dunpollo to see how I did it.

Thanks for the advice, as ever, when I get a few mins I'll take a look. You sig still suggests bases 0.90 is abandoned! But I see more vids on youtube so I've plenty to watch!

[OhioBob]

Ah yes my 1600Dv is the total not just the ejection Dv. Why would I want to just fly by? lol...

My comment in which I quoted 1100 m/s was in reference to the opening post. The OP wrote "my engine must fire continuously for 60 minutes to get to Duna", which is a reference to the ejection burn only. Obviously ejection and insertion are two separate burns that would not be continuous.

[MoridinUK]

My comment in which I quoted 1100 m/s was in reference to the opening post. The OP wrote "my engine must fire continuously for 60 minutes to get to Duna", which is a reference to the ejection burn only. Obviously ejection and insertion are two separate burns that would not be continuous.

Actually given how long his burn is they could end up continuous! Tee hee j/k Sorry I was confused..

[smjjames]

Instead of using the nuclear rockets for the ejection burn out of Kerbin orbit, I just either use a stronger rocket engine or the second (or third) stage which I used to get out of the atmosphere.

[Invader Myk]

This is an artifact of patched conic navigation where it is assumed that 100% of the DV is applied instantaneously. Obviously, even with the most powerful engines, this is impossible. There are two work-arounds for this (that I'm aware of). First and easiest, start your burn about 2/3 of the total burn time before the node. This effectively applies half of the thrust (because a vessel's TWR increases as fuel is burnt) on each side of the manoeuvre node. The second method is to create several nodes with less than 10 second burn times roughly 12 seconds apart. This better simulates the application of DV over time.

edit:

Also, with a TWR so low that you need to burn for an hour to get a Kerbin-Duna transfer orbit, it is essential to learn how to do a powered gravity assist. Better tutorials can be found online than I'm giving here. Essentially you choose a transfer window that brings you in close proximity to Mun (periapsis as close as possible to 20km) with the periapsis behind Mun's path of travel. This will cause Mun's gravity to accelerate the craft (and in a relativistic gravity simulator decelerate Mun by the exact amount of energy as the vessel is accelerated). The "free" DV gained by this can be augmented by performing a burn at periapsis. Then when you get into Duna's SOI you can lose speed by getting an Ike encounter with the periapsis ahead of Ike's path of travel. This can cut your total DV from engines by almost 50%, and more importantly for a low TWR vessel it breaks the DV of two insanely long burns into 4 merely painfully long burns.

Edited February 10, 2015 by Invader Myk
second thoughts

[Brainlord Mesomorph]

Just posted my tutorial on how to do exactly this!

http://forum.kerbalspaceprogram.com/threads/110213-Long-Burns-Interplanetary-Trajectories-with-Low-TRW-%28and-No-Math%29?p=1726429#post1726429

[juanml82]

I'd still like a picture of the ship that requires a 60 minute burn to make it to Duna using nuclear engines

[smjjames]

I'd still like a picture of the ship that requires a 60 minute burn to make it to Duna using nuclear engines

Probably a nuke engine strapped to a huge tank and the Isp is very low.

Though I'm curious here as well.

[Laie]

This is an artifact of patched conic navigation where it is assumed that 100% of the DV is applied instantaneously.

Nitpick: patched conics is not at fault here. Even in real life, many to most burns are assumed to be instantaneous. Whether that works out or not solely depends on whether the burn is relatively short; relative, in this case, to the duration of one orbit.

The bodies in KSP are insanely dense: surface gravities on a scale we're familiar with, but the size of asteroids. Even Jool is still smaller then our Earth. A "low" orbit in KSP is going round and round at insane speed.

In LKO, your craft is covering about ten degrees per minute, but two-minute burns are still very close to the mark, and even five minutes work reasonably well. Just look how far you craft moves in five minutes -- personally, I'm amazed that maneuver nodes work as well as they do.

The precision of long burns increases dramatically if you go to a higher orbit, with a period of a few hours. Of course, that wastes fuel and therefore this forum and other sites are filled with advice on perigee kicking and whatnot.

[Superfluous J]

Thanks for the advice, as ever, when I get a few mins I'll take a look. You sig still suggests bases 0.90 is abandoned! But I see more vids on youtube so I've plenty to watch!

Oops I always forget to update my .sig

I'll fix it ... when I'm done with the devnotes thread.

[Thorazine]

Hello Red Iron Crown, Scarecrow88, OhioBob, eddiew, juanml82, cantab, GoSlash27, Pecan, and Laie.

Thank you all for your great suggestions.

The first thing I'll try is adding more nuclear engines to my rocket. Since I first posted I've seen a few rockets with multiple nuclear engines.

Also, I like the idea of first placing my rocket in a highly elliptical orbit, and starting my burn from the apoapsis (I believe that is what your suggestion is, GoSlash27 and Laie).

I tried to insert a screen shot of my rocket, but I kept getting the error that said that the text I entered was too long.

The rocket consists of two Rockomax Jumbo-64 fuel tanks stacked on top of each other, with a single nuclear engine and a one-man capsule on top.

[Laie]

Also, I like the idea of first placing my rocket in a highly elliptical orbit, and starting my burn from the apoapsis (I believe that is what your suggestion is, GoSlash27 and Laie).

Noooo! All burns should happen at periapsis. Brainlord has written a howto: http://forum.kerbalspaceprogram.com/threads/110213-Long-Burns-Interplanetary-Trajectories-with-Low-TRW-%28and-No-Math%29

The rocket consists of two Rockomax Jumbo-64 fuel tanks stacked on top of each other, with a single nuclear engine and a one-man capsule on top.

The whole payload is one capsule? You don't even need one orange tank, much less two. Two nukes and one orange tank for twenty tons of payload will get you to every destination in the game. For most missions, you can afford to carry either more payload or more nukes. For Duna, you could even mount one gas-guzzling skipper for a much shorter burn and could still get there and back again.

You know about transfer windows, do you?