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Duna/Ike combo mission planning


MPDerksen

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I have a total of 4 missions, currently, and 100 days to plan before my launch window.

  • Rescue Kerbal from Ike orbit (fairly inclined orbit, actually)
  • Collect and return Duna Ejecta from Polar lowlands on Ike
  • Collect and return Duna Stone from Midland canyon on Duna
  • Transfer crew between vessels over Duna

Mission Plan is currently to head straight to Ike first.  Land to get the Ejecta, and do the rescue on the way back up.  Then head over to Duna, land to get the stone, and NOT dock when I get back, but EVA over to fulfill the Transfer requirements (I'm honestly not sure what those requirements actually are).  I was going to have a basic lander can on top of the MK3 pod, and return.

My biggest question is how to plan my dV for this.  I've done several down and back from both Ike and Duna, but never both in the same trip.  I also know I can refuel the lander easily enough by just docking to my main Xfer craft.  Bonus is that I don't need any engineer to repack my chutes, since it's not coming home again anyway.

Second question is how to control a craft with multiple cockpits.  Jeb (or Val) will fly solo, so is it as easy as which ever one he/she is currently in?

Last question.  I'm going to have docking ports on top of both the lander can and the MK3.  Do I launch with them docked together?  Or have everything "upright" and flip the lander in orbit?  I never understood why to re-orient the craft after launch. But if I just stack them, do I put a regular decoupler on top of the docking port of the bottom part, and then build the lander on top of that?  I don't want to find that anything is blocking the docking port later.  I suspect I need to refuel for trip #2, and then completely drain the lander for the trip home.

All thoughts are welcome on this.

Michael

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You don't need a decoupler there, the bottom (as is: from the big ship) docking port acts like one, so you can just build on it and then reconnect both in orbit, like in Apollo missions

Multiple cockpits are not a problem once you set "control from here" on the correct one. (I just do that every time to be sure even if I don't need it)

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Cool, thanks.  Although WHY we have to flip them round in orbit instead of just launching it put together in the first place?  It's easy enough to do, just never understood the "why" part.

For the dV, just add a bunch of math?  I'm going to assume zero aero-capture, but do it anyway.  Anything I get will be a bonus.

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34 minutes ago, MPDerksen said:

Cool, thanks.  Although WHY we have to flip them round in orbit instead of just launching it put together in the first place?  It's easy enough to do, just never understood the "why" part.

For the dV, just add a bunch of math?  I'm going to assume zero aero-capture, but do it anyway.  Anything I get will be a bonus.

The escape tower with the humans is on top for launch. We bury our Kerbals in fairings cause our engines/tanks don’t spontaneously combust.

Edited by SlinkyMcman
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1 minute ago, SlinkyMcman said:

Pretty much. Usually when my launches fail I just revert. That’s a form of “launch escape system” in a matter of speaking.

A fair plan.  Less fun when you land too hard on Eve, snap a landing leg and roll down a hill to sea level....  Then you have a choice of a games toughest rescue or a revert to a prior save and feel like it's cheating...

Any insight into the rules for "transfer crew between vessels" contract?  I assume a rescue counts since there is an EVA involved?  Or just separate my main craft, and EVA Jeb from the main part to the lander?  I don't want to get all the way out there to realize I need a SECOND vessel to complete it

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19 hours ago, SlinkyMcman said:

I don’t think you need to bring another mission/ship/vessel.

I am afraid that you need two vessels that started independently from Kerbin to fulfill a transfer crew contract.

I am not sure if you can dock them at LKO and do the transfer to Duna combined.

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4 hours ago, CBase said:

I am afraid that you need two vessels that started independently from Kerbin to fulfill a transfer crew contract.

I am not sure if you can dock them at LKO and do the transfer to Duna combined.

Probe-driven re-fuel tanker to Duna.  Jeb with an extra seat goes to Ike.  Does the rescue and lands to collect the Ejecta.  Then they move over to Duna, refuels and lands to get the Stone and head home together?  I assume I could "dock" with a grabber.

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  • 2 months later...

Months later, I'm now ready to actually do this....  

Doing, for me, the hardest part of the game:  calculating the required dV.  If I could finally really understand this part, the enjoyment of KSP would double.

Using the dV map here's what I have.  Kerbin --> Ike (landed) = 5330.  Not sure if I was do my orbital rescue before landing, or on the way back up, but need to add some fuel for that part too.
Xfer from Ike -->  Duna orbit to dock and refuel, do the whole "transfer crew" thing = 960
Duna landing -->  map says 1450, but we have parachutes, so....  ?
Duna --> Kerbin = maybe 2200?

I'm thinking a 3 stage craft.  ~4,000 dv to get into 100K orbit, plus some extra.  Transfer stage of ~~2,000 to get me around Ike.  Then a lander that has ~2,000 and a bunch of parachutes?  I can refuel before and after the trip to the Duna surface.  

All this sound reasonable?  I'm not trying to create mega-craft, or be perfect in my fuel.  I'm learning how to plan missions, and then build a craft around those plans.  

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This is the report for my Dunpollo mission: https://imgur.com/a/l181y1r

It's not the same mission profile, but it's similar in that I had to land on both Duna and Ike in the same mission. I have the numbers I used for mission planning and ship design in the album.

Spoiler

TvMyM4E.jpg

Dunpollo is the most complex mission I've done so far. I could probably just throw together a really big ship with 10,000 m/s dV, stick a lander on it, and have it work. But it's a lot more satisfying to me to actually sit down, plan it out, and design a ship. In that light, Dunpollo breaks down into the following phases:

A. Launch to low-Kerbin orbit [3400 m/s]

B. Transfer to Duna and set up in a low polar orbit (~60 km) [2300 m/s]

C. Land on Duna, then return and redock with the main ship [2000 m/s]

D. Transfer from Duna orbit to a low polar orbit around Ike (~15 km) [900 m/s]

E. Land on Ike, then return and redock with the main ship [1000 m/s]

F. Transfer from Ike back to low-Kerbin orbit and land [2200 m/s]

Total dV: 11,800 m/s. This number is a bit more than the standard dV map would suggest because it accounts for plane changes to/from polar orbits. For the science!

 

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On 3/25/2020 at 1:08 PM, CBase said:

I am afraid that you need two vessels that started independently from Kerbin to fulfill a transfer crew contract.

I am not sure if you can dock them at LKO and do the transfer to Duna combined.

Yea, I think the two craft need a different launch ID. With this in mind though, launching 2 vessels can make it easier for the part below:

On 6/9/2020 at 10:51 PM, MPDerksen said:

Doing, for me, the hardest part of the game:  calculating the required dV.  If I could finally really understand this part, the enjoyment of KSP would double.

Using the dV map here's what I have.  Kerbin --> Ike (landed) = 5330.  Not sure if I was do my orbital rescue before landing, or on the way back up, but need to add some fuel for that part too.
Xfer from Ike -->  Duna orbit to dock and refuel, do the whole "transfer crew" thing = 960
Duna landing -->  map says 1450, but we have parachutes, so....  ?
Duna --> Kerbin = maybe 2200?

I'm thinking a 3 stage craft.  ~4,000 dv to get into 100K orbit, plus some extra.  Transfer stage of ~~2,000 to get me around Ike.  Then a lander that has ~2,000 and a bunch of parachutes?  I can refuel before and after the trip to the Duna surface.  

All this sound reasonable?  I'm not trying to create mega-craft, or be perfect in my fuel.  I'm learning how to plan missions, and then build a craft around those plans.  

Well, if your are separating your craft, which you should be, then its gets less straightforward. You should be doing orbital rendezvous... no sense in bringing everything down to duna, just to bring it back up again, ditto for Ike.

A LKO to Duna intercept costs you 930+130= 1060 m/s... Call it 1100 to have some margin. A duna intercept can allow for aerobraking/aeorcapture, where you can lower your Ap to get an Ike intercept "for free". You may want to split craft here for maximum efficiency, with one craft continuing to aerobrake, while the other circularizes around Ike. Lets say 50m/s for maneuvers for the Duna ship, and 180 (call it 200 to have a margin) for your Ike lander to go into a low circular orbit.

The Duna ship so far needs 1150 m/s to get into a low circular Dunar orbit, and the Ike ship needs 1300 to get into a low orbit around Ike. Now your Ike lander needs about 800 m/s to land on Ike and return to an orbit of Ike. From there it needs about 200 m/s to get into a low duna orbit... you may not want to bother with orbital rendezvous around Ike to save 200 m/s, but you could (I'd recommend just leaving a fuel tank with a docking port in orbit, no need to duplicate power, command, and control functions)

So, 2300 from LKO for your Ike ship to get to Ike, land on it, and then go to Duna where it can rendezvous with your Duna ship.

Meanwhile, your Duna ship needs 1150 to get into LDO. A lander would need... maybe 100 m/s for propulsive breaking, and lets say 1500 for ascent, so 1,600. So, if it was a transfer and lander stage by itself, 2750 m/s to get to the surface of duna, and back to orbit.

From LDO, you need about 750 m/s to get back to Kerbin (about 570 m/s to get back from low Ike orbit, but you havea contract to redezvous in Duna orbit). So, to one of your ships, add 750 m/s. Lets say you add it to your Duna craft.

Then a Direct Ascent profile for duna (with aerobraking) would need 3,500 m/s. And a direct ascent profile for Ike> Duna rendezvous would need 2300 m/s.

I don't know how inclined the orbit you need at Ike is, but lets add 400 m/s for that: 3,500 for the Duna direct ascent, 2,700 for the Ike direct ascent> Duna rendezvous

Your duna craft can be lighter if you do an orbital rendezvous, in which case your craft to go to LDO and back needs just 1150+750= 1900 m/s, with the first 1150 done with the Duna lander attached, and the next 750 m/s done without the duna lander.

All these numbers are, of course, after reaching LKO

 

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I would send a single rocket to land on both Duna and Ike and do the rescue with a Klaw on the front, and a second rocket just to carry some fuel. Send the fuel tank to Duna and the rescue rocket to Ike.

Land on Ike, collect the ejecta and then using a klaw grab the crew pod for the rescue contract and transfer burn to Duna but release the pod just before crossing over into Duna’s SOI, transfer the stranded Kerbal to the rescue rocket in Duna’s SOI, rendezvous with fuel tank if necessary to refuel then land on Duna, grab the stone, return to orbit and refuel again then go home.

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