Help With Duna Re-Usable?

[ThePresD]

Hi!

I have a ambitious rocket program idea to get to Duna With.

It consists of a refueling station (75km orbit) which will hold reusable duna landers/transfer craft. Also, I'll need some SSTO ideas for a reuseable orbital craft I can use to shuttle astronauts to this station's staging area, once that is complete.

This is the reusable stage, it has around 1500 deltaV. I think that's enough to get to duna. If not help me out to improve it's delta V while keeping it at a minimal docking size. Also it MUST be reusable.

Another picture.

I also am planning to put a refueling station in orbit around Duna, which I'm not sure how to do yet. Any help with this project is MUCH appreciated, and I'm not too well with maths and all that so try to put it in stupid person language. Thanks!

[Jouni]

Reusability becomes easier, if you split the ship into a transfer stage and a lander. A simple Duna landing requires almost as much delta-v as getting to Duna's orbit from LKO and returning back to Kerbin, so you really don't want to carry any extra stuff to the surface.

The transfer stage is essentially a big fuel tank with 2-4 nuclear engines. Add the usual stuff (SAS, RCS, batteries, solar panels / RTGs, docking ports, and a probe core), and you get an unmanned ship that can go pretty much anywhere and function as a refueling base once it gets there. If one big fuel tank isn't enough, you can always send another transfer stage without payload. If you attach the engines in the same way as in your current ship, the fuel in the small tanks should be enough to return an empty refueling base to LKO for refueling.

A Duna lander should need about 1500/2000 m/s delta-v (atmosphere / vacuum), assuming that you use parachutes to kill the speed for landing. Building the lander around the Mk1-2 Command Pod is a good idea, because then you usually don't need separate SAS modules, batteries, and RCS fuel tanks. Personally I prefer to use a large docking port at the bottom of the lander to connect it to the top of the transfer stage, because it provides a rigid enough connection for the heavy three-kerbal lander.

SSTO crew shuttles can be quite simple. The one I use was originally intended as a Laythe lander, but it found better use, when it easily reached the orbit during flight tests.

[Vanamonde]

Shameless self-promotion: the first craft in my reuseable interplanetary ship thread has made multiple trips to Duna, Eve, and Dres, while hauling 70+ ton payloads.

Oops. I think I mis-read your post. Mine is an interplanetary ship, not an SSTO.

Edited February 9, 2014 by Vanamonde

[capi3101]

I built a spaceplane that delivered three Kerbals to a space station in orbit of the Mun and returned safely. Currently am working on one that will haul a full orange tank into orbit and come back (it's the come back part what's giving me headaches at the moment).

Lemme pull up that imgur album real quick.

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Jouni's got a good idea - it generally will save you some headaches if you separate your landers from the transfer craft. You could build the ships smaller that way.

As for the Duna refueling station, there's no real reason why you couldn't use the same design as what you have at Kerbin. You'd just need to build a transfer stage for it. We can hammer that out pretty easily - what's the mass on one of those station pieces? That is two of them docked together, right?

I do wonder where your solar panels are on that station, but that's another matter altogether.

[Kerba Fett]

Have you checked to see if switching those nukes for LV 909's gains you dV? Their thrust is only 10 kN less but they're 1.75 tons lighter each. Also, if you're going to Duna, is it for career for the science? If so you might want to work a lab in there.

I did an extended mission to Minmus for my second trip as a proof of concept for Munar operations and later Duna.

The main ship is my Mobile Orbiting Support Station. When fully fueled it has the same capacity as a single orange tank. To bring it up from the surface I had to have it only half fueled due to its mass. It uses a Poodle since they're fairly light and have good vacume isp. It has just under 4000 m/s dV when fueled and carries 400 units of monoprop in radial tanks. Docked to the MOSS is a lander with 2 science Jr's and 2 goo canisters. Also docked is a data courier.

The mission profile is to have the MOSS arrive first and establish orbit. Two of the crew move from the capsule to the lab module.

The lander then follows on it's own transfer vehicle. Once the lander reaches orbit it docks with the MOSS. Any fuel remaining in it's transfer stage is moved to the MOSS. The lander then undocks and after moving away from the station detaches from it's transfer stage. The lander then deorbits and lands on the surface to take material studys, goo observations, crew reports, eva reports, and surface samples. The lander than does a suborbital hop to a new site and repeats the process. Anything with a 100% transmit value is sent. All other data is kept for delivery.

The lander then returns to orbit and docks with the MOSS.

The kerbal in the command pod goes EVA and recovers the data from both goo containers and both science Jr's. He also gets the data from the lander capsule then returns to the MOSS command pod. Taking the data packs from the instruments disables them, but the crew in the lab can repair them for the next mission. The lander refills it's fuel and RCS tanks from the MOSS and undocks for another trip to the surface.

Once enough science data is gathered a courier is dispatched from kerbin. The ship is small. parachute, Mk1 pod, RCS tank and thrusters, probe size landing gear and a sheilded docking port. I use a mod called Tweak Everything that allows me to start with the sheild open to put it on a transfer stage. It's about 1.8 tons so a fairly small rocket will get it off the ground and on it's way to Minmus. While it's only propulsion is RCS it's got just under 700 m/s worth of it so you can enter minmus orbit and dock with lots left. It's actually a bit too responsive when docking and I'd prefer for it to be a bit weaker. For a Duna mission you'd need a larger transfer stage that would be refueled at duna and used to get back to kerbin.

Once the courier docks, he EVA's and takes the collected data from the command pod of the MOSS. He reboards his ship, undocks and returns to kerbin using the atmosphere to brake. The parachute insures a soft landing and the legs keep you looking professional. You can even direct your landing site on the way down with any remaining RCS fuel.

Once the tracking station recovers the ship you get return bonuses on all that science data while the crew back at minmus is free to continue collecting more.

For my Duna mission I'm thinking of a similar system but the first stage would be putting a kethane operation on Ike for orbital refueling. I can get a tanker to minmus with a reasonable payload of fuel, but I think Duna would be much tougher.

Anyways, perhaps you can use some of the ideas here for your Duna mission.

[capi3101]

Hell with it - I'm bored. Let me see if I can figure out your station fragment mass on my own:

Looks like you've got the following:

1x Protective Rocket Nose Mk7 (0.4 tonnes)

1x RC-L01 RGU (.5 tonnes)

1x Jumbo-64 Fuel Tank (32 tonnes)

1x Large ASAS Module (0.2 tonnes)

2x FL-R1 RCS Fuel Tank (6.8 tonnes)

1x Z-4K Battery (.2 tonnes)

12x Z-100 Batteries (.06 tonnes)

9x Clamp-O-Tron Docking Ports (0.18 tonnes)

8x PB-NUK RTGs (0.64 tonnes; took me a couple of tries to figure out what those were, also answers my question of where your solar panels are)

8x RCS Blocks (.4 tonnes)

TOTAL MASS: 41.38 tonnes. Two of them put together would be 82.76 tonnes. Does that sound about right?

A few redundancies are obvious in the design - you don't need both batteries and RTGs (unless you intend to transmit data). I'd also submit that it would take a very long time for you to go through the amount of fuel contained in two large RCS tanks, but you do what you want to there. The nose cones are also not really necessary - you could do something more useful there such as swap it out for something functional such as a senior docking port.

Overall though that's not that much in terms of mass - if you send two fragments to Duna seperately, you can rendezvous them in orbit. Your transfer stage only needs enough delta-V for a one way trip (~1100 m/s). Say 1400 for a nice margin of error. Four nuclear engines mounted off the bottom of FL-T100 tanks, mounted radially to the side of an X200-16 tank and connected with struts and fuel lines, will give you 1379.66 m/s of delta-V, enough to make the trip comfortably with a little to spare. Go with FL-T200s on the sides if you'd like a little extra for the rendezvous.

Total Mass would be 62 tonnes. I'd recommend a '>Zenith IX booster (they still work despite not having been updated for a few versions). The Zenith VII would be pushing it despite what it says (could be how I pilot it, of course).

EDIT: Incidentally, that 1100 for the transfer stage is what you need for your transfer craft; the trip from Duna to Kerbin takes much less (even with a comfortable margin for error). 1300 makes Duna orbit.

Your 1489 craft oughta be able to make the trip as is. The only questionable bit is whether it has sufficient TWR to lift off of Duna. With three NERVAs, 61 tonnes is your absolute limit; you're less than that, though over the 38 tonnes you'd want for a nice 1.6 TWR. I might suggest putting an I-beam outboard running parallel and alongside your nukes, with the lander legs attached to the end of them - that'll widen your base and make it less likely you'll tip over.

Yeah...so far you have a good looking system. Five Kerbal lander too. It's just a matter of figuring out how you're going to refuel the Duna station.

Edited February 10, 2014 by capi3101