Getting to Duna?

[UndyingWar]

It it possible to get to Duna if it's behind Kerbin? Or do I have to wait an entire year for it to be in the correct position again? What are some good ways to get there in a timely manner?

[Tex_NL]

Of course it is.
All planets and moons are reachable at any moment. But it will cost you a shed load of dV to actually make it to your destination. Hohmann transfers are not the only option, but the are the cheapest.

[UndyingWar]

4 minutes ago, Tex_NL said:

Of course it is.
All planets and moons are reachable at any moment. But it will cost you a shed load of dV to actually make it to your destination. Hohmann transfers are not the only option, but the are the cheapest.

What's a Hohmann transfer?

[Tex_NL]

3 minutes ago, UndyingWar said:

What's a Hohmann transfer?

Hohmann transfer

Edited February 13, 2016 by Tex_NL

[Sir_Robert]

59 minutes ago, UndyingWar said:

What's a Hohmann transfer?

You know how you rendezvous 2 ships together while in Kerbin orbit? That's a Hohmann

[Snark]

Basically, you have three choices:

1. Launch during a good window, using a Hohmann transfer
2. Try to go there direct & fast, using stupidly large amounts of dV at both ends of the trip
3. Take a slow roundabout way that ends up being similar time-to-Duna as if you had just waited for the window

For example, here's an approach that will get you to Duna for a reasonable amount of dV (though not as good as a Hohmann transfer) when it's not the right window.  Let's say Kerbin is somewhat ahead of Duna, which is the reverse of what you want.

1. Launch from Kerbin, such that you eject from its SoI going parallel to Kerbin's orbit around the sun, with enough excess velocity that it raises your Ap to the level of Duna's orbit.
2. Coast up to Ap.  You're now at Duna's orbit, but you're too far in front of Duna.
3. Burn prograde to raise your Pe (which starts down at Kerbin's orbit) up to where you are (so you're circular) and then some-- thus your former Ap (where you are now) becomes your Pe.  As you raise your Ap beyond Duna's orbit, you'll notice the closest-approach marker for Duna sliding closer to you.  Raise the Ap until you get an encounter.
4. Now you just have to wait for a full orbit (i.e. slightly longer than one Duna year) until you get your encounter.

...You see the problem there.  Step 4 is slow.  It would have been faster to just wait until Kerbin comes around to a good launch window and do the transfer then.

[Reactordrone]

If Duna is behind you a little bit a standard Hohmann transfer will leave you ahead of Duna so you'll need to boost a little higher than Duna's orbit in order to slow down and let Duna catch up. You'll use more fuel getting into the higher orbit and you'll be faster when you encounter Duna requiring more fuel to slow down, but if you're not far past the transfer window the delta v penalties shouldn't be too bad.

[UndyingWar]

8 hours ago, Snark said:

Basically, you have three choices:

1. Launch during a good window, using a Hohmann transfer
2. Try to go there direct & fast, using stupidly large amounts of dV at both ends of the trip
3. Take a slow roundabout way that ends up being similar time-to-Duna as if you had just waited for the window

For example, here's an approach that will get you to Duna for a reasonable amount of dV (though not as good as a Hohmann transfer) when it's not the right window.  Let's say Kerbin is somewhat ahead of Duna, which is the reverse of what you want.

1. Launch from Kerbin, such that you eject from its SoI going parallel to Kerbin's orbit around the sun, with enough excess velocity that it raises your Ap to the level of Duna's orbit.
2. Coast up to Ap.  You're now at Duna's orbit, but you're too far in front of Duna.
3. Burn prograde to raise your Pe (which starts down at Kerbin's orbit) up to where you are (so you're circular) and then some-- thus your former Ap (where you are now) becomes your Pe.  As you raise your Ap beyond Duna's orbit, you'll notice the closest-approach marker for Duna sliding closer to you.  Raise the Ap until you get an encounter.
4. Now you just have to wait for a full orbit (i.e. slightly longer than one Duna year) until you get your encounter.

...You see the problem there.  Step 4 is slow.  It would have been faster to just wait until Kerbin comes around to a good launch window and do the transfer then.

Ah okay. That makes sense. Thanks for the reply. So would it be normal for me to just speed up time for a year or so until I get into the right window? Is that what most people do? To me that feels weird, like my space program has just been sitting there doing nothing for a year.

[Ketatrypt]

3 hours ago, UndyingWar said:

Ah okay. That makes sense. Thanks for the reply. So would it be normal for me to just speed up time for a year or so until I get into the right window? Is that what most people do? To me that feels weird, like my space program has just been sitting there doing nothing for a year.

 

I know what you mean, I am still on the verge of interplanetary trips, but, nothing is lined up properly. Instead of waiting the complete year or whatever, I am building up a minmus station, and other things like that. It takes almost a half month to do a minmus round trip, so the time goes by pretty quick once you have some missions going.

[Sir_Robert]

7 hours ago, UndyingWar said:

Ah okay. That makes sense. Thanks for the reply. So would it be normal for me to just speed up time for a year or so until I get into the right window? Is that what most people do? To me that feels weird, like my space program has just been sitting there doing nothing for a year.

Yes, don't be afraid to make big jumps in timewarp. Otherwise you'll be forever stuck in the Kerbin system. You could do a lifetime of spacetravel in the Kerbin system before you get a single rocket to another planet if you don't timewarp (and that's a good way to get bored)

[Plusck]

11 hours ago, UndyingWar said:

Ah okay. That makes sense. Thanks for the reply. So would it be normal for me to just speed up time for a year or so until I get into the right window? Is that what most people do? To me that feels weird, like my space program has just been sitting there doing nothing for a year.

I don't like doing that either. The resulting problem is that I necessarily have a ton of interplanetary trips going on at the same time. So I have bits of paper with all the different launch windows marked out, and the times of each of my upcoming maneuvres in each year. I should use the alarm clock mod...

In the end that means that I rarely warp forward more than about 20-30 days at a time. However, it's really frustrating waiting for the longer-distance trips to actually get there. Times between development of a vehicle and actually testing it on the ground feel like the years that pass in-game.

[Snark]

12 hours ago, UndyingWar said:

So would it be normal for me to just speed up time for a year or so until I get into the right window? Is that what most people do? To me that feels weird, like my space program has just been sitting there doing nothing for a year.

 

10 minutes ago, Plusck said:

I don't like doing that either. The resulting problem is that I necessarily have a ton of interplanetary trips going on at the same time. So I have bits of paper with all the different launch windows marked out, and the times of each of my upcoming maneuvres in each year. I should use the alarm clock mod...

In the end that means that I rarely warp forward more than about 20-30 days at a time. However, it's really frustrating waiting for the longer-distance trips to actually get there. Times between development of a vehicle and actually testing it on the ground feel like the years that pass in-game.

I'm exactly in the same place as @Plusck.  I also don't like to just let it sit around for long periods of time, and make up for that by having lots of missions going on at the same time... and also I'm not using Kerbal Alarm Clock, for no very rational reason.

I know that there are some players who cheerfully warp ahead for years at a time, and regard Kerbal calendar time as a free, unlimited resource.  I just can't make myself do this.  I have a few "role-playing" impulses-- not many, but a few-- mainly due to identifying with the Kerbals.  And one of those impulses is that it bugs me for large amounts of in-game time to pass.  To me, game calendar time is a scarce resource to be conserved, and I just can't make myself view it any other way.

So, yeah, lots of parallel missions, which avoids the "wasting time" problem in exchange for the "keep track of everything at once" problem. 

[Sir_Robert]

15 minutes ago, Plusck said:

I don't like doing that either. The resulting problem is that I necessarily have a ton of interplanetary trips going on at the same time. So I have bits of paper with all the different launch windows marked out, and the times of each of my upcoming maneuvres in each year. I should use the alarm clock mod...

In the end that means that I rarely warp forward more than about 20-30 days at a time. However, it's really frustrating waiting for the longer-distance trips to actually get there. Times between development of a vehicle and actually testing it on the ground feel like the years that pass in-game.

You really should. It's super easy

[GeneralVeers]

Fourth option: exit Kerbin's SOI retrograde, dive close to Kerbol and gravity whip around it. Takes more fuel to get your periapsis close to the Sun, but the trip down and back up can be done in 40 days.

[Vegetal]

Well in real life, space programs always have a lot to do in terms of planning, but to actually launch an interplanetary mission..... Yeah, you have to wait for the window. The penalty is enormous.

Man, think about the supposed planet nine. Unless there's a big propulsion technology breakthrough, we're not sending probes there anytime soon. It's the time of the universe..... Things take long....

[Sir_Robert]

53 minutes ago, Vegetal said:

Well in real life, space programs always have a lot to do in terms of planning, but to actually launch an interplanetary mission..... Yeah, you have to wait for the window. The penalty is enormous.

Man, think about the supposed planet nine. Unless there's a big propulsion technology breakthrough, we're not sending probes there anytime soon. It's the time of the universe..... Things take long....

We send a probe to Pluto, and that one spent 10 years en route. A few more years to get out to planet 9 won't be much extra

[Snark]

3 hours ago, Sir_Robert said:

We send a probe to Pluto, and that one spent 10 years en route. A few more years to get out to planet 9 won't be much extra

Pluto is under 40 AU away.  The hypothetical Planet 9 has a semimajor axis of 700 AU, with a periapsis of at least 200 AU.

So, by our current best guesses, it's at least 5 times farther away than Pluto, average 17 times farther away, potentially 30 times farther away.

So, no, not going there any time soon.

[Vegetal]

4 hours ago, Sir_Robert said:

We send a probe to Pluto, and that one spent 10 years en route. A few more years to get out to planet 9 won't be much extra

Check the numbers man. As Snark said, the planet has a semimajor axis of 700 AU. Voyager 1 is at 134 AU, and that was launched at the seventies. And by pure orbital mechanic logic, it's probably close to it's apoapsis.

So yeah. No.

[Mahnarch]

On 2/14/2016 at 11:37 AM, Snark said:

 

I'm exactly in the same place as @Plusck.  I also don't like to just let it sit around for long periods of time, and make up for that by having lots of missions going on at the same time... and also I'm not using Kerbal Alarm Clock, for no very rational reason.

I know that there are some players who cheerfully warp ahead for years at a time, and regard Kerbal calendar time as a free, unlimited resource.  I just can't make myself do this.  I have a few "role-playing" impulses-- not many, but a few-- mainly due to identifying with the Kerbals.  And one of those impulses is that it bugs me for large amounts of in-game time to pass.  To me, game calendar time is a scarce resource to be conserved, and I just can't make myself view it any other way.

So, yeah, lots of parallel missions, which avoids the "wasting time" problem in exchange for the "keep track of everything at once" problem. 

You and I are a lot alike.

 

When my model trains mess up/derail I try to fix it "the proper way", instead of just grabbing the cars and re-railing them.

Just grabbing and moving is a big no-no, unless it's like the Amtrak fubar last year (or, whenever that was).