Mission to Duna

[Iforgotthis]

After 515 hours on KSP, I am (shockingly) yet to send Kerbals beyond the Kerbin system. There's a Duna transfer window coming up, and I don't know what to do. I will be sending a variety of things, one of which will be a manned mission. I want it to be as realistic as possible though, so I have a couple of questions:

1.) If NASA sends man to Mars at some time in the future, do you think they will launch the entire ship from Earth in one rocket, or send up parts separately and dock them in orbit?

2.) Which engine is best for interplanetary travel? I've been hovering around the nuclear engine because I've heard it's quite good for long distance, but is there any that is better (I have KW Rocketry too)?

3.) How many Kerbals would be a reasonable number to send? I've been thinking three, but that seems monumentally too few for such an important mission. There's a mod part that is a 7 seated capsule which looks very interesting. Do you think 7 is too many for a first mission?

It'd be great to hear your opinions. I know in KSP there's lots of free range to do whatever you want, but I quite like realism too, so if anyone knows realistic methods then that'd be great to hear about.

Thanks for your time!

Edited August 13, 2014 by Iforgotthis

[UmbralRaptor]

1) Both are possible, with a tendency for assembly in Earth orbit. Though there's also an architecture that involves multiple launches without so much docking. That said, KSP tends to make direct ascent much easier/more practical.

2) For most designs, the LV-N offers the most ÃŽâ€V / greatest mass efficiency, but requires greater care in lander design.

3) In science/career, at least 1 for EVA/crew reports. For a test mission, I'd be tempted to say 0 to minimize overall craft mass.

[Frank327]

1) If mars would be as easy to reach and return from as Duna, I think they'd do it in one launch. I don't know how difficult it is in real life though. Duna isn't a lot more difficult to reach (in terms of the design/size of your rocket) than the Mun.

2) For interplanetary travel in general the nuclear engine is the best because it is by far more effective. Duna is close by enough though that it could be smarter to use LV-909's and Poodle engines to make landing easier. They're still great for interplanetary stuff because of how lightweight they are.

3) In my career I only take 1 but in real life I think 2 or 3 minimum. I don't see the point of taking more crew than that. After all it's very difficult (in real life) to take a lot of crew with you because of weight, oxygen and food requirements. And I think 2 or 3 crewmembers should be able to do all the necessary tasks in the mission.

If you want to do it both smart and realistic, I'd have the return to kerbin stage, and the interplanetary transfer + landing stage seperate. All of the landing gear, science equipment and empty fuel tanks used to get to Duna can be left on the surface of the planet and then you can take only the cockpit, fuel, electricity equipment and the engine back with you.

[cantab]

1) They'll do it the same way as the Chinese do. /pessimism. NASA has quite a bit of experience in orbital assembly with the ISS, so it could well be done that way.

2) The LV-N is the go-to interplanetary engine, its fuel efficiency is streets ahead of anything else barring the ion engine, which has its own drawbacks. That said, if you make full use of aerobraking then Duna orbit and back needs about 1700 m/s of delta-V, and even taking 2000 for safety that's low enough that the Rockomax 48-7S might give you a lighter ship, depending on your desired TWR.

3) 3 seems right, if only because it's what Apollo used. "Realistically" it's better to land two, not just one, so that one can help the other if needed, and it's better not to leave the orbiter unattended. On the other hand if you want to send seven send seven.

[tg626]

I'll be sending 5 jeb, bill, Bob, and 2 "red shirts". Lander carries 2.

Based on Von Kerman's... Er I mean Von Braun's 1968 IMIS proposal

Edited August 10, 2014 by tg626

[Wanderfound]

After 515 hours on KSP, I am (shockingly) yet to send Kerbals beyond the Kerbin system. There's a Duna transfer window coming up, and I don't know what to do. I will be sending a variety of things, one of which will be a manned mission. I want it to be as realistic as possible though, so I have a couple of questions:

1.) If NASA sends man to Mars at some time in the future, do you think they will launch the entire ship from Earth in one rocket, or send up parts separately and dock them in orbit?

2.) Which engine is best for interplanetary travel? I've been hovering around the nuclear engine because I've heard it's quite good for long distance, but is there any that is better (I have KW Rocketry too)?

3.) How many Kerbals would be a reasonable number to send? I've been thinking three, but that seems monumentally too few for such an important mission. There's a mod part that is a 7 seated capsule which looks very interesting. Do you think 7 is too many for a first mission?

It'd be great to hear your opinions. I know in KSP there's lots of free range to do whatever you want, but I quite like realism too, so if anyone knows realistic methods then that'd be great to hear about.

Thanks for your time!

1) I don't think NASA will get a manned mission to Mars before they cease to exist. However: orbital docking isn't just about construction. Even with a single-piece spacecraft you can save a lot of launch weight if you send it up with empty tanks and then refuel it in orbit.

2) Look at the vacuum ISP stats; higher is better. In some circumstances TWR can compensate for inferior ISP, but that's mostly about ultralight probes, not heavy manned missions. You'll likely find this useful: http://wiki.kerbalspaceprogram.com/wiki/Parts#Liquid_Fuel_Engines

3) With this, it's all about whatever feels best for you. Nobody's done it yet, so nobody knows. More people gives more options, but also more chance for interpersonal conflict. See http://www.jamesoberg.com/04142000assualt_rus.html

You would probably enjoy this book: http://www.maryroach.net/packing-for-mars.html

You'd probably also enjoy this mod: http://www.curse.com/ksp-mods/kerbal/221022-tac-life-support

Edited August 10, 2014 by Wanderfound

[Taki117]

1) do what you will, It is easier to get to Duna with a single launch, but docking in orbit isn't unheard of.

2)For interplanetary you want the Nuke, unless you don't have the Nuke in which case use the KW mono propellant engine (looks like the Apollo service module engine) Mono prop is lighter than LFO so you have a higher TWR for a given craft mass if your engine burns it.

3) Generally I send 3-4 on my interplanetary missions. That way, if something goes wrong there is always a kerbal to take over. (I don't play with random failures, but I like to pretend)

[JebNeedsHelp]

Since 1) and 2) have been answered already, I'll just touch on 3). My first two Kerballed Duna landings were solo flights. When I felt better about sending more Kerbals, I built a 10-Kerbal colony ship, and successfully landed two of them. My most recent colony was this "Leaning Tower of Duna", which holds 22 Kerbals. And so far, every trip to Duna has been a one-way trip. My next Duna goal is to start bringing some long-time colonists home.

Here's what happened to one of my Leaning Towers on the Mun. Oops. I have since done a redesign.

http://i83.photobucket.com/albums/j314/Goof112/screenshot12.png' alt='screenshot12.png'>

[juanml82]

As for 3), if it's for science, I'd say two: one to Ike and the other to Duna. The reason for that is that, IMO, Ike and Duna require different landers. Of course, it's also a matter of role playing, and whether you want to take the kerbals back to Kerbin or if they are there to stay.

I think a minimalistic mission to Duna consists of two ships:

A lighter one heading for Ike: SRBs+Ascend stage to get into Kerbin's orbit. Then you have an interplanetary stage with nuclear engines (or maybe even a leftover Skipper or one of the new engines from the last of your ascend stage. Duna is doable with chemical rockets) and a lander based on a single LV-909 or Poodle. The lander might have enough fuel left after leaving Ike to return to Kerbin on it's own, but it doesn't hurt to have the interplanetary stage around to dock just in case.

A heavy lifter can take the mission to Duna itself in one go. IIRC, the lander must have about 2,500 m/s left when it lands to be able to return to orbit, so you'll probably want a staged lander. Use parachutes, specially drogues, as they open higher. You should count on expending some fuel to slow down, but chutes can slow you down and save you precious fuel for your return journey. Unless you don't plan to return, of course.

Beyond that, it's up to you. You might want to set up permanent bases on Duna or Ike, if you use the kethane or karbonite mods you can take send more ships to set up an extraction facility. If you want to max science you might consider taking the large mobile lab as well. You have several biomes: space high, space low, upper atmosphere, flight and surface. You can take several science jr. in your landers, specially if you plan to leave them behind. Or you can take space high before capture, reset the science jr and the goo, get space low and upper atmosphere when aerobreaking, reset them and then get flight on your way to the surface and surface before abandoning the science jr and goos in Duna forever.

[Pecan]

(2,500m/s is the round-trip, landing and re-orbit, requirement)

Crew: I prefer reusable stations, landers and transfer tractors to single-mission disposable ships so I'd normally have; 2 in the lab, 1 station commander, 1 tractor pilot. They can fight over who gets to fly the lander(s) ^^.

[Iforgotthis]

Thanks everyone! This has all been super helpful.

I've decided to send 4 kerbals to address the isolation; 2 stay in orbit 2 go to the surface.

As for a single launch or not, still undecided. Most likely a single launch but I'll see how it goes while I'm building it.

I'll be using several nuclear engines

The only problem left is the idea of extended zero gravity, so I'll have I use a centrifuge which requires a suspension of belief.

I'll make sure to update this OP to show you the final thing

[Wanderfound]

Thanks everyone! This has all been super helpful.

I've decided to send 4 kerbals to address the isolation; 2 stay in orbit 2 go to the surface.

As for a single launch or not, still undecided. Most likely a single launch but I'll see how it goes while I'm building it.

I'll be using several nuclear engines

The only problem left is the idea of extended zero gravity, so I'll have I use a centrifuge which requires a suspension of belief.

I'll make sure to update this OP to show you the final thing

You'll want to make your centrifuge big, then. As in "a kilometre or two wide".

Small centrifuges set up Coriolis currents in your inner ears. In the memorable phrase of one research paper on the subject, this tends to be "explosively nauseogenic".

[Iforgotthis]

You'll want to make your centrifuge big, then. As in "a kilometre or two wide".

Small centrifuges set up Coriolis currents in your inner ears. In the memorable phrase of one research paper on the subject, this tends to be "explosively nauseogenic".

That could be problematic... I don't know how I could overcome the zero gravity problem. The idea of the entire ship spinning through space is unnerving and an inconvenience. Any ideas?

[Wanderfound]

That could be problematic... I don't know how I could overcome the zero gravity problem. The idea of the entire ship spinning through space is unnerving and an inconvenience. Any ideas?

If we had an answer, NASA'd be using it already. So far, the only methods we have for generating artificial gravity without making people constantly puke are to use an impractically huge centrifuge or maintain a constant 1G acceleration (not really possible without magical reactionless hyper-efficient thrusters). Spinning the ship is no use unless the ship is the size of a small town.

It's a major problem for any future Mars mission. Extended exposure to microgravity causes adaptations in balance and vision. Eye movement is closely linked to the vestibular system; it's why we can keep our eyes steady when our heads are moving. These adaptations are fine so long as you stay in microgravity, but they're totally crippling once you come back down.

For quite some time after returning to a non-microgravity environment, your sense of balance is roughly equivalent to someone with near-fatal alcohol poisoning, and your eyes constantly flick in random directions. I've seen footage of a Shuttle mission where the pilot almost flipped the thing onto its tail at the moment of touchdown, because his eyes chose that moment to go haywire.

Astronauts generally spend their first week back on Earth throwing up and unable to stand. The first human on Mars is going to celebrate their achievement by having a good long lie-down.

[Wanderfound]

BTW: anyone interested in the microgravity vestibular stuff should look at the work coming out of this lab: http://www.psych.usyd.edu.au/humanfactors/?page_id=1445

They had the office next to mine back when I was a researcher; they'd occasionally borrow our rats for direct brain stimulation studies. They've done quite a bit of work on the Vomit Comet, and some of their experiments have gone up on NASA missions.

[Kevin Kyle]

Twice (once in the previous build and again this weekend) I have taken this ship, Kassandra in this thread right here a few post down from the top. http://forum.kerbalspaceprogram.com/threads/76858-The-Stock-Craft-Repository-%28v0-24%29 It has a pdf that comes with it an explains most of the mission details. Its a great first trip to Duna ship. Do an aerobrake when you arrive at Duna. It seems with the recent build that I used more fuel than the first time and I dont think I would of had enough without aerobraking but I did make it. Has lots of science on board and a nice little rover. I also used the calculator here http://alexmoon.github.io/ksp/ to help figure out the launch times to and from Duna. Kassandra is a well thought out design and pdf and much kudos to H2O for the work he done on this ship. I have also used the Eve comet http://forum.kerbalspaceprogram.com/threads/78852-Want-to-go-to-Eve-and-back-Try-this and LaytheX which I cant find a link for but both were in the last build, not this one. Just a FYI. BTW, Kassandra is an awesome ship as well as the others I mentioned.

[Starwaster]

A suspension of belief?

Usually it's disbelief that requires suspending....

[/PEDANTRY]

[MarvinKitFox]

1.) If NASA sends man to Mars at some time in the future, do you think they will launch the entire ship from Earth in one rocket, or send up parts separately and dock them in orbit?

2.) Which engine is best for interplanetary travel? I've been hovering around the nuclear engine because I've heard it's quite good for long distance, but is there any that is better (I have KW Rocketry too)?

3.) How many Kerbals would be a reasonable number to send? I've been thinking three, but that seems monumentally too few for such an important mission. There's a mod part that is a 7 seated capsule which looks very interesting. Do you think 7 is too many for a first mission?

1) realworld mars mission?

Likely 1-3 launch for actual vehicle. Engines, fuel, stores etc. This launches weeks before mission.

1 launch for crew. Likely an orion-type capsule, with inflatable habitats ala Bigelow.

And before any of this, 1-3 launches to mars of landers with the return vehicle, supplies, ground habitat etc. Quite possibly with in-situ resource gathering for methalox for return. No Ways nasa will launch the crew before they have a known means of return already prepped and fuelled waiting for them.

2) is KSP? Nuke. one nuke, plenty fuel, and a truckload of patience. Not that you really *need* a nuke's efficiency for Duna, but for a first trip it will give you a good amount of elbow-room in your delta-v.

3) Funny, *my* kerbals typically solo. In a command chair. They like the view.

If you aim for realism, crew should be no less than 5, prefer 7-9. Assuming human type personality and social interaction and group dynamics.

1 will go bonkers.

2 will soon become 1, a.k.a. space murder.

3 will become 2 gang-up on 1.

4 will be 2 gangs of 2.

Starting at 5, the group dynamics tend to be complex enough to not resolve/stagnate in the 1.5 years a Mars trip will take. The "extras" in a 7-9 crew is to complexify the mix, provide redundant secondary but critical skills (such as surgeon ability), and quite frankly... spares, in case of attrition.

[Trann]

A suspension of belief?

Usually it's disbelief that requires suspending....

[/PEDANTRY]

I like the cut of your jib, sir.

As for the topic at hand,

1) I'd put money on multiple launches and much time in orbit while preping to leave Earth SOI. Cautious, deliberate, and certain.

2) Nukes. Definitely nukes. My most successful style is to stage tanks and have a pair of nukes at the top of the stack so you can dump the weight as they empty. Be prepared for long burn times if you're hauling a lot of mass. Definitely pad your delta-v.

3) I chose to send 2 my first time. Witnesses and all that. Lately, solo.

Good luck.

[capi3101]

1) Mars was one of the potential mission sites for the proposed Constellation Project as I recall, and there's a challenge here on the forums that's been going on for a few versions now that replicates that project. Constellation would've seen craft docked in orbit before heading on to their final destinations. Got an imgur album of the Duna portion of my entry in the challenge; others too but that's the only one relevant to the question.

2) Nope. You want nukes. One nuke gives you good efficiency but crappy thrust; more gives you better thrust but cuts into your efficiency. Myself, I use clusters of fou; seems to be a good balance. At least, it did a few versions ago.

3.) How many Kerbals would be a reasonable number to send? I've been thinking three, but that seems monumentally too few for such an important mission. There's a mod part that is a 7 seated capsule which looks very interesting. Do you think 7 is too many for a first mission?

3) Naw, send as many as you like. The more you send, the more Internets you earn. Me, I sent six in that album. Could've sent more if I felt like leaving a few behind.

[Jouni]

If you aim for realism, crew should be no less than 5, prefer 7-9. Assuming human type personality and social interaction and group dynamics.

1 will go bonkers.

2 will soon become 1, a.k.a. space murder.

3 will become 2 gang-up on 1.

4 will be 2 gangs of 2.

Starting at 5, the group dynamics tend to be complex enough to not resolve/stagnate in the 1.5 years a Mars trip will take. The "extras" in a 7-9 crew is to complexify the mix, provide redundant secondary but critical skills (such as surgeon ability), and quite frankly... spares, in case of attrition.

I'd say that a crew size of 3-6 would be realistic, with 5 as the optimal number. When group size reaches 7, there's a real danger of the group splitting into two groups. On a long mission isolated from the rest of the world, that would be pretty bad.

[cantab]

The LV-N is recommended as the go-to engine and rightly so, but for Duna it's not the only viable option. I knocked up two sketches of Duna ships, using the "Apollo-style" orbiter/lander arrangement.

Specs were as follows:

3-Kerbal one-stage orbiter has at least 528 m/s of delta-V for the return trip, to be taken sans lander, and 1166 m/s for the outward, obviously taken with lander. These are 10% margins over this delta-V map:http://wiki.kerbalspaceprogram.com/w/images/7/73/KerbinDeltaVMap.png . That's a fairly slim margin I admit, but not unreasonably so.

2-Kerbal one-stage lander has about 1500 m/s Duna atmo delta-V (a little of which will be needed for touchdown) and plenty of TWR, and weighs about 7 tons. That's a more generous margin which I think is desired for a lander.

With the lander, the orbiter has a Kerbin TWR of about .35, adequate for interplanetary travel.

The version with one LV-N on the orbiter weighed in at 16.7 tons, while the version with two 48-7S's was 18,6 tons, just 11 percent heavier. So while in this case the nukes do win, there's not an awful lot in it.

Nuke ship: https://flic.kr/p/opocuK

48-7S ship: https://flic.kr/p/opoqgq

[Iforgotthis]

Thanks again everyone, lots of useful stuff.

It appears there's a consensus that between 3-7 is a good range for a first Duna mission. Because it's a first mission, I'll be taking four. Two will remain on board the orbiter, and two will descend to the surface. Therefore nobody is left alone.

Again, there's wide agreement that the nuclear engine is the best. I was thinking of using three, is that too many?

I think in the scheme of things there will have to be at least two launches; one for the interplanetary ship and one for the crew. Maybe three, but most likely only two.

Edited August 12, 2014 by Iforgotthis

[Taki117]

Again, there's wide agreement that the nuclear engine is the best. I was thinking of using three, is that too many?

I'm going to address this first. Depending on the weight of your interplanetary ship 3 might actually be too many. Nukes are heavy, meaning if you dont need more than one dont use more than one. that being said, if you have a TWR in LKO of less than .5 you might want to add another.

[Laie]

Again, there's wide agreement that the nuclear engine is the best. I was thinking of using three, is that too many?

I'm going to address this first. Depending on the weight of your interplanetary ship 3 might actually be too many. Nukes are heavy, meaning if you dont need more than one dont use more than one. that being said, if you have a TWR in LKO of less than .5 you might want to add another.

There's those who say that one should never-ever use more than one Nerva as any more than that will cut into your Delta-v. Personally, I think it matters whether I spend three, eight or twenty minutes waiting for the transfer burn to complete. A Kerbin-TWR of 0.5 is quite a lot for interplanetary missions, but if you want to go no further than Duna, it can be done and won't be all that expensive, either.

Plus: really low thrust and the resulting need for many-minute burns will reduce efficiency. When I sent my Ion Probe to Eve (TWR=0.16), executing a 2000m/s maneuver node actually cost me 2200m/s.