Some tips for getting manned craft past Kerbins SOI?

[reconwarrior21]

So, i'm not new to the game, however with the exception of a handful of manned missions, and a rover, to the Mun. I've pretty much kept to atmospheric, and LKO. I was wondering if y'all have any tips for the campaign, and getting vessels out of Kerbin orbit, and to the great beyond that makes KSP great. 

Thanks

[Snark]

Welcome to the forums!

Really, it just comes down to the following:

1. Building a craft with enough dV
2. Knowing how to navigate interplanetary trips
   • A. ...by doing an appropriate transfer burn
   • B. ...by being familiar with orbital mechanics and approach strategies

#1 is a whole topic in its own right, not sure how your skills are there, or what kind of advice.  Main thing is to decide what mission you want to do, figure out how much dV you need (e.g. by looking at a dV map), then work on building a ship that has that much dV.

#2A is pretty simple, just use a launch planner.  My favorite is http://ksp.olex.biz .  Just tell it your origin and destination planet, and the height of your parking orbit above the origin, and it tells you how big a burn you need, in what direction, at what time, with easy-to-understand visual diagrams.

#2B takes a bit more practice... but if you get really good at navigating among Kerbin, Mun, and Minmus, you pretty much have that one covered.

For navigation practice, here's a useful litmus test:  do a transfer between low Mun orbit and low Minmus orbit.  If that's straightforward for you, then you're ready to go interplanetary.    If that's hard to figure out and you struggle with it, then it's probably worth practicing that until you're good at it, then you're ready!

Anyway, the above is just talking in very general terms about what the areas of major challenge are-- it's hard to get a lot more specific without more of a feel for just what areas you need help with.  Can you elaborate a bit more?

Edited February 11, 2016 by Snark

[reconwarrior21]

3 hours ago, Snark said:

For navigation practice, here's a useful litmus test:  do a transfer between low Mun orbit and low Minmus orbit.  If that's straightforward for you, then you're ready to go interplanetary.    If that's hard to figure out and you struggle with it, then it's probably worth practicing that until you're good at it, then you're ready!

Anyway, the above is just talking in very general terms about what the areas of major challenge are-- it's hard to get a lot more specific without more of a feel for just what areas you need help with.  Can you elaborate a bit more?

I've got the construction part mostly down, same for figuring out when to launch. Problem lies in fuel efficient navigation, return trips, and successfully leaving Kerbins SOI without getting stuck adrift.

[wibou7]

Interplanetary manned missions are easy if you plan them right.

If you want your kerbals to make it home,the best tip I can give you is to always plan the missions in two parts. First, send out a full tank of fuel, the biggesr you dare to, to where you want to go. THEN you send the kerbals. 

The tank serves two purposes.

One, it makes sure you have a buffer in case something goes wrong, just plan the mission as if the tank wasn't there and you will always have enough Delta-V to make it home no matter how wrong your estimates went. 

Two, and most importantly, sending the tank there act as a test of how good your plan / preparation is for the mission. If you can't, or barely make your tank into foreign orbit, if it explodes while aerobreaking or if anything go kerbal, you will know you must go back to the drawing board and revisit your design. If you make it easily, then the manned mission should be a breeze.

[Geschosskopf]

6 hours ago, reconwarrior21 said:

So, i'm not new to the game, however with the exception of a handful of manned missions, and a rover, to the Mun. I've pretty much kept to atmospheric, and LKO. I was wondering if y'all have any tips for the campaign, and getting vessels out of Kerbin orbit, and to the great beyond that makes KSP great. 

Thanks

Welcome to the forums!

Anyway, if you can get to Mun, you can get anywhere.  It's all the same stuff you already know, just on a bigger scale, and with 1 complication.  That complication is that you can go to Mun any time you want to, just put a node on your orbit around Kerbin at the point where Mun is just above the horizon, and away you go.  This happens at some point in every orbit around Kerbin so at most you have to wait about 20 minutes before the transfer burn.  But when going to other planets, you have to wait until the other planet is in an analogous position, which might take the better part of a year to happen as both Kerbin and the target orbit around the sun.  And the further away the target planet is, the more the position of the node on your orbit around Kerbin changes from the target being just above the horizon like with Mun.

There are thus 2 angles you need to know:   the phase angle, which is the relative positions of Kerbin and the target planet compared to the sun, and the ejection angle, which is where on your orbit around Kerbin to place the maneuver node.  There are a number of tools that tell you these things.  The easiest (as in requiring the lest amount of figuring outside the game) is MechJeb's "Advanced Transfer to Another Planet).  Set your target planet, call this up, tell it you want the porkchop ploit, pick the point on the plot that looks best, and tell it to create a node.  The plot is exactly the same as that used by the website @Snark mentioned but the advantage here is that MJ will put the node at exactly the right ejection angle without you having to eyeball it, and also set it for the correct time.  Then you use another mod called Kerbal Alarm Clock (KAC) to create an alarm for that maneuver node.  And then you're set.  You can warp ahead at full speed and KAC will stop time just before it's time to do the burn.  Then you can either do the burn yourself or have MJ's autopilot do it for you.  And in the meantime, if the burn is months/years in the future, you can be flying other missions without fear that you'll miss the interplanetary transfer window because KAC will keep that from happening.

So, that takes care of the navigation.  The only remaining hurdle is making sure your ship as the dV and TWR required for the trip.  For this, consult a dV map, and use either MJ or Kerbal Engineer Redux (KER) to show you during construction how much dV and TWR you have.

Thus, the whole process is kinda the reverse of this.  It goes like this:

• Design the mission, such as deciding if you're going to land on the planet or not, and return to Kerbin or not.  If you're going to land, then your lander needs the TWR to take off at the target.  If you're going to return, you need the dV for a round trip.
• Consult a dV map to see how much dV you need for each step along the route.
• Build the ship using KER or MJ to determine if you have the TWR for the lander (if necessary) and the dV required to get there (and return, if that's intended)
• Use KAC to set an alarm some days ahead of the next transfer window to the target and warp (or fly other shps) until the alarm goes off.
• Launch the ship into an LKO parking orbit when the KAC alarm goes off.
• Use MJ to create the maneuver node for the transfer burn.
• Use KAC to create an alarm for the transfer burn and warp until that stops you.
• Do the transfer burn.

Once you're on your way, you'll very likely have to tweak your trajectory mid-flight to fine-tune your approach to the target.  Create this node (either manually or with MJ) and set a KAC alarm for this burn.  Warp ahead (or fly other ships) until that alarm goes off.  Then do the tweak burn  make sure KAC creates an alarm for when you enter the SOI of the target planet, and warp ahead (or fly other ships) until you get there.  Once in the target's SOI, it's all stuff you've done before.

 

[reconwarrior21]

Thanks for all the tips guys! Some really informative stuff. I think i'll be spending a few days designed a new lander and launcher, and doing some trial runs to the Mun and Minmus (Or both in one go) and back. If everything checks out, my crew will hopefully be setting foot upon another planet! @wibou7 Thanks for the suggestion, wouldn't have thought about launching an automated precursor mission, usually I just hurl massive amounts of Kerbals and fuel at my target until we succeed. One other question, best locations for orbital, or planetary, resupply stations? Thanks again.

[Snark]

On 2/12/2016 at 5:53 PM, reconwarrior21 said:

Problem lies in fuel efficient navigation, return trips, and successfully leaving Kerbins SOI without getting stuck adrift.

If you've got the "pick a transfer window and burn direction" bit down, then the biggest remaining piece you need for fuel-efficient navigation is to make friends with the Oberth effect.

Without getting into a lot of technical jargon, what it boils down to is that rockets give you more bang for your buck if you do your burns when you're traveling fastest, which means at low altitudes.  When departing a body, you want your parking orbit to be low.  When arriving at a new body, you want your Pe to be as low as possible when you approach, and do your capture burn right at Pe.  (And, of course, use aerobraking if you're somewhere that it's possible.)

If you want to send a one-way trip (e.g. an unmanned probe), both Duna and Eve are good first destinations:  easy to get to, don't need much dV to get there, they have atmospheres so it's easy to land.

The big difference there is that Duna is a whole lot easier to come home from again.    If you want to send a land-and-return mission, Duna's a good place to get your feet wet, figuratively speaking.  Done properly (and starting from LKO), it only takes about 100 m/s more to land on Duna than it does to land on the Mun.  (Coming home from Duna is quite a bit more expensive than coming home from the Mun, though.)

As with any land-and-return destination, designing your lander for the target environment is essential.  In the case of Duna, this means taking advantage of its atmosphere when landing.  Generally this means:

1. a couple of drogue chutes to get you slowed down from 500 m/s to 250ish m/s.
2. a regular chute to slow from 250 m/s down to a few dozen m/s
3. a brief burst of rocket thrust to kill speed before landing

(This works better than trying to pack on enough parachutes to land safely-- the atmosphere there is so thin that you'd need way too many parachutes.  It's less mass to take just a few chutes, and use a smidgeon of fuel to cushion the landing.)

If you're more ambitious, you could include an ISRU miner for Ike and refuel there, but it's up to you how fancy you want to get when starting out.