Landing Belly First

[MrOsterman]

So I've built myself my first "space ship".  It's a MK3 core fuselage with 2.25m parts attached along the sides to create a wider base, the parts running "along" the main body.  I've got the sides of those lined with Thud engines pointed "down" when it is sitting flat/ belly down to the planet surface, and an obscene number of landing struts to support it when it does touch down.  The top of the vessel is also lined with parachutes for descent into any kind of atmosphere, though I think that engine braking can be pretty solid on most planets.  My current mission is a trip to and from Duna with landings on Minmus and Ike to refuel before making the jump into Solar orbit to set up the transfers.

What I'm bumping into is any tricks to manage the landings.  My first thought was to simply tell the pilot to align the ship to the the "Radial" vector in the gimbal and hold that position on the way down.  The problem is that I set the gimbal to measure relative to the surface, I lose the the Radial option.  Usually when I do a "butt first" landing, I just tell my pilot to align the ship Retrograde and go from there, burning as needed to slow to a nice touch down.  Last night I managed a landing "by hand" holding the artificial horizon steady and eyeballing the "translation" vectors to be sure I was coming "straight down".

Eventually I'd love to master the landing of coming in at an angle, burning the belly engines just before landing to slow significantly, turning it flat, and then dropping down.  For now I'm only as good as burning Retrograde until I come to a near stop, dropping straight at the surface, and flipping over to a Belly Flop before impact and burning the belly engines there.

 

[steuben]

set a probe core or a docking port on the spine or the belly facing up and set "control from here".

 

[tutike2000]

1 hour ago, steuben said:

set a probe core or a docking port on the spine or the belly facing up and set "control from here".

 

^This.
Attach a probe or docking port that points 'up' by any means that you like.
The Editor Extensions mod will let you attach a probe core directly.
If you want to keep you game vanilla, you can add a radial attachment node, docking port, girder, anything that will have a node, then plop that probe on top. Or just use a single docking port and 'Control from here'

[MrOsterman]

5 hours ago, steuben said:

set a probe core or a docking port on the spine or the belly facing up and set "control from here".

 

I had a feeling it was an easy thing.  No probe cores (I'll spend 700k on something but not want to spend the extra on a probe core when there's a perfectly capable pilot to fly it) but I do have a dorsally mounted docking port.  Next landing I'll try that out as my "control from here" and that should point my "up/down" along something my pilot can manage to keep the ship stable.

 

[FyunchClick]

One thing to keep in mind if you use SAS in surface mode to hold prograde (which when controlling from a belly mounted docking port keeps your belly pointed into the direction your moving relative to the surface, which is where you want to point your engines to kill speed) is that when you touch down, if you bounce a bit the prograde hold will try to flip your craft upside down, so switch it to stability assist just before you touch down.

[Snark]

23 minutes ago, FyunchClick said:

One thing to keep in mind if you use SAS in surface mode to hold prograde (which when controlling from a belly mounted docking port keeps your belly pointed into the direction your moving relative to the surface, which is where you want to point your engines to kill speed) is that when you touch down, if you bounce a bit the prograde hold will try to flip your craft upside down, so switch it to stability assist just before you touch down.

Best to use a dorsal docking port, and "hold retrograde" -- unless your brain is constructed very differently from mine, it's very difficult to control a ship when the thrust direction isn't the same as the look direction.

Also, SAS hasn't had that "flip when landing" problem in a while.  Yes, it used to do that, but recently (was it 1.0 where they fixed this?), they made it is so that the navball switches automatically over to just SAS hold if the speed goes below 1.0 m/s.

[FyunchClick]

On ‎14‎-‎1‎-‎2016 at 0:14 AM, Snark said:

Best to use a dorsal docking port, and "hold retrograde" -- unless your brain is constructed very differently from mine, it's very difficult to control a ship when the thrust direction isn't the same as the look direction.

Also, SAS hasn't had that "flip when landing" problem in a while.  Yes, it used to do that, but recently (was it 1.0 where they fixed this?), they made it is so that the navball switches automatically over to just SAS hold if the speed goes below 1.0 m/s.

Wrt dorsal vs ventral, I'd agree for ships where you land on your main engines, as you also need to line those up to maneuver nodes etc. However if you're doing something like Kuzzters Hummlebee (with belly vernor engines for touching down) that doesn't really work for practical and aesthetic reasons (the cargo bay hatch is on top).
As to brain wiring, as long as you put on the port in such a way that the crafts true nose is pointing up when the port is facing forward, pulling back on the stick still raises your nose and pushing forward drops it, so it works as expected. Yaw and roll are swapped but that's true for dorsal as well.  

And indeed, SAS gets switched to stability assist if you come in gentle enough but I still had a couple of times (in 1.04 at least) where I either bounced hard on touchdown or braked a bit too much so I gained altitude again, and in both cases never went slow enough to trigger the switch (thus flipping my craft).

To make a final plug for vernor engines for landings (especially belly mounted), not only are the RCS controls much nicer for touch downs because you can pulse them, they also help with keeping the ship stable during landing because they are RCS engines, and stability tends to be a belly lander problem as the COM tends to shift significant as fuel is consumed. With regular engines, you either need enough gimbal or tweak the output manually before you go in (or during if you consume enough) which is a bit of a pain. Just bind the vernor engines to a hot key so they don't mess with regular RCS activities like docking where they pack too much punch. Their biggest weakness is that you need enough of them so they don't really do it for heavy haulers.

 

[Snark]

11 minutes ago, FyunchClick said:

Wrt dorsal vs ventral, I'd agree for ships where you land on your main engines

Yah, that's mainly what I was talking about.

12 minutes ago, FyunchClick said:

To make a final plug for vernor engines for landings (especially belly mounted), not only are the RCS controls much nicer for touch downs because you can pulse them, they also help with keeping the ship stable during landing because they are RCS engines... Their biggest weakness is that you need enough of them so they don't really do it for heavy haulers.

Agreed, vernor engines can come in handy.  The cases where I've found them most useful is as an assist for when I'm landing a plane somewhere that has really thin atmosphere, like Duna.  (Or Lave, playing with the New Horizons mod; it has about a quarter the atmosphere and twice the gravity of Duna.)

Landing a plane somewhere that has very thin atmosphere is challenging, because the stall speed is so high that you need to land while still traveling very fast.  That can make landing a real pain, especially if the ground is hilly as Duna tends to be.

Sticking a couple pairs of Vernors under the craft (with a hotkey toggle) can really help a lot.  Turn them on when in final landing approach, so you can go slower without stalling (and the added benefit that when you pitch up just before landing, that means the Vernors are pointing slightly forward and therefore help to slow you down even more).

They also help with takeoff, since they help to lift the nose up  (I like to put one pair up front and one in the back).

[fourfa]

Another option if RCS parts just aren't powerful enough: tweakscale up some vernors?  I haven't tried it...

[MrOsterman]

Hmm... I'll have to experiment maybe but I'm not sure I can pack enough Verners, with the required fuel, to fully break and land a belly down ship with my required payload of an ISRU, two drills, and passenger compartments.  I tried to do a landing of what I ~thought~ was a small craft with those requirements on the Mun using 4 Terrier engines and made a GLORIOUS new crater.  And it wasn't fuel mass that cost me, it was all "required" payload.

And yes I've thought about seperating the lander from the processor but honestly I just can't handle the "work" of doing multiple lift launches of Ore which requires either engineering a mining vessel able to lift all of the ore I need to top the tanks, or it means taking the processor down to to the surface.

So far my top designs use mutliple Thuds as my landing engines as they seem to be able to get the required thrust, but I do run into some stability problems on landing (usually taking 2-3 tries to get the thrust levels right to bring me down softly.  Maybe the solution is to go back and mix in some more Verners to help out with the stability.

And I didn't think to hotkey them all in so as not to burn too much fuel doing orientation changes with RCS..... that's a good call.

 

[WhiteKnuckle]

50 minutes ago, MrOsterman said:

Hmm... I'll have to experiment maybe but I'm not sure I can pack enough Verners, with the required fuel, to fully break and land a belly down ship with my required payload of an ISRU, two drills, and passenger compartments.  I tried to do a landing of what I ~thought~ was a small craft with those requirements on the Mun using 4 Terrier engines and made a GLORIOUS new crater.  And it wasn't fuel mass that cost me, it was all "required" payload.

And yes I've thought about seperating the lander from the processor but honestly I just can't handle the "work" of doing multiple lift launches of Ore which requires either engineering a mining vessel able to lift all of the ore I need to top the tanks, or it means taking the processor down to to the surface.

So far my top designs use mutliple Thuds as my landing engines as they seem to be able to get the required thrust, but I do run into some stability problems on landing (usually taking 2-3 tries to get the thrust levels right to bring me down softly.  Maybe the solution is to go back and mix in some more Verners to help out with the stability.

And I didn't think to hotkey them all in so as not to burn too much fuel doing orientation changes with RCS..... that's a good call.

 

Aerospikes are your friend.

[MrOsterman]

5 hours ago, WhiteKnuckle said:

Aerospikes are your friend.

They won't work on atmosphere free spaces will they?

[WhiteKnuckle]

9 minutes ago, MrOsterman said:

They won't work on atmosphere free spaces will they?

Despite "aero" being in their name, no they work just fine in vacuum.

 

Probably the "best" engine in the game, nearly the same Vac ISP as the Terrier, but with better atmo ISP and 3x the thrust. No gimbaling though so make sure you have other ways of control.

[FyunchClick]

9 hours ago, MrOsterman said:

Hmm... I'll have to experiment maybe but I'm not sure I can pack enough Verners, with the required fuel, to fully break and land a belly down ship with my required payload of an ISRU, two drills, and passenger compartments.  

(...).

And I didn't think to hotkey them all in so as not to burn too much fuel doing orientation changes with RCS..... that's a good call.

 

Kuzzter posted his Hummlebee craft file for download. It has an ISRU, full science stripping package, and seats 4, and it made it to Duna and back so it'll handle the Mun just fine (in fact I took my own replica there before he posted it and I was shocked at how nice that handled on airless bodies). You could download it and give it a try. 

Vernors are not very fuel efficient. To conserve fuel, you can bleed off most of your orbital speed with the main engines that will have a much better ISP and TWR, and switch to vernors at around 1-2 kms up and a hundred or so m/s left to break. Or try the "Cobra" maneuver from his story (on planets with atmosphere).

The action group is more to prevent the vernors from flinging you way off course than for fuel preservation, as they are much too powerful, making docking maneuvers nearly impossible (just tabbing translate-up shortly will add one or more meters per second to your speed).