Landing Rocket

[DarkHawkGames]

I'm sorry if I'm asking this in the wrong place, but I may have come up with an idea. So I was reading about the Space Race earlier, and it mentioned something about landing with 'retro rockets' and that got me thinking. Would it be very effective to use a very small 'retro stage' for Mun landings, to help slow your descent? What do you guys think?

[dangerhamster]

Weeeeell I tried parachutes but they don't work....

But in seriousness any engine on a Mun lander is a retro rocket so you are better off budgeting the DV needed to land into the total needed to return to Kerbin rather than a dedicated landing stage. Thus saving weight that can be used for other things.

On a sort of related note I do have a habit of putting a couple of Puff engines and a monoprop tank into my multiple crew return capsules as a sort of emergency brake.

 

[DarkHawkGames]

Well my thinking was, a very small tank underneath your main 'landing' stage would help save you fuel for your return. When you used it all, you could decouple it and leave it behind, so it wouldn't weigh you down on take-off.

[Harry Rhodan]

13 minutes ago, DarkHawkGames said:

Well my thinking was, a very small tank underneath your main 'landing' stage would help save you fuel for your return. When you used it all, you could decouple it and leave it behind, so it wouldn't weigh you down on take-off.

You can of course use staging in any design. That is basically what this whole game is about. Isn't it?

 

You mentioned using a life support mod in your other thread. Do you use Kerbal Engineer or any other mod that gives you a delta v readouts of your stages? That would help you building your stuff in a more straightforward manner and you could see how much additional stages/engines/tanks influence the performance of your crafts.

[DarkHawkGames]

1 minute ago, Harry Rhodan said:

You can of course use staging in any design. That is basically what this whole game is about. Isn't it?

 

You mentioned using a life support mod in your other thread. Do you use Kerbal Engineer or any other mod that gives you a delta v readouts of your stages? That would help you building your stuff in a more straightforward manner and you could see how much additional stages/engines/tanks influence the performance of your crafts.

I do, but I'm thinking about starting over without life support that way I can get used to doing the interplanetary stuff without having to worry about supplies.

[Venusgate]

This is purely a gameplay preference. As someone who's landed (barely) 20m tall, 10-15 part rockets on the moon, I can say there is no necessity to having an eagle style lander. And going for cost effectiveness: one engine with a lot of fuel in one stage is often cheaper than 2 stages, each with their own engines.

That said...having eject-able fuel pods/landing gear is just good kerbal fun.

[DarkHawkGames]

12 minutes ago, Venusgate said:

This is purely a gameplay preference. As someone who's landed (barely) 20m tall, 10-15 part rockets on the moon, I can say there is no necessity to having an eagle style lander. And going for cost effectiveness: one engine with a lot of fuel in one stage is often cheaper than 2 stages, each with their own engines.

That said...having eject-able fuel pods/landing gear is just good kerbal fun.

I remember watching a let's play by someone, I think it may have been Scott Manley, and he had radial fuel tanks for his landing stage with a Science Jr. in the middle, and it even had jettison-able nose cones to save weight. 

[Venusgate]

1 minute ago, DarkHawkGames said:

I remember watching a let's play by someone, I think it may have been Scott Manley, and he had radial fuel tanks for his landing stage with a Science Jr. in the middle, and it even had jettison-able nose cones to save weight. 

What he didn't tell you is all the added cost and weight of hauling decouplers to all those parts

[DarkHawkGames]

14 minutes ago, Venusgate said:

What he didn't tell you is all the added cost and weight of hauling decouplers to all those parts

The decouplers probably weighed more than the nose cones. I tried doing a similar thing with three radial tanks but no nose cone decouplers, but it always flipped out of control when I tried it.

[bewing]

One nice thing about decoupling the nosecone is that it gives your kerbonaut a place to stand on top of your rocket. They can often climb up there to leave for (and it gives them a place to land when coming back from) an RCS-powered EVA. To avoid the whole "ladders all the way to the ground" thing.

[RizzoTheRat]

16 hours ago, DarkHawkGames said:

The decouplers probably weighed more than the nose cones. I tried doing a similar thing with three radial tanks but no nose cone decouplers, but it always flipped out of control when I tried it.

The nosecones weigh next to nothing and hopefully pay for themselves with reduced drag on launch.

This is my early game Mun lander, dropping the radial tanks and landing gear when taking off from the Mun saves a chunk of weight for the trip home, which I reckon it could probably just about do with an FL-T100 tank in the center instead of a 200, but would need a pretty efficient pilot on the way out.  The radial tanks take it from LKO to the Mun surface without a transfer stage, which is cheaper than having an extra transfer engine and lighter than having extra drop tanks for the transfer and smaller landing tanks.  Dunno which approach would give the lightest launcher but first stages are pretty cheap anyway.  Didn't have the Spark engine at this point so I guess that would change things a bit.

[Snark]

Staging the descent is certainly an option.  I tend not to use it much for Mun or Minmus, since the dV requirements are generally pretty manageable.

I'm more likely to use it when I'm somewhere that needs scads of dV between surface and orbit, and doesn't have an atmosphere to assist landing.  (I'm lookin' at you, Tylo.)

 

[DarkHawkGames]

Rizzo, what do you use the Spark engines for? It seems to me like it wouldn't slow it down fast enough. Maybe on a Minmus landing? But it surely wouldn't provide enough thrust to take off again.

[RizzoTheRat]

39 minutes ago, DarkHawkGames said:

Rizzo, what do you use the Spark engines for? It seems to me like it wouldn't slow it down fast enough. Maybe on a Minmus landing? But it surely wouldn't provide enough thrust to take off again.

It's been a while so I can't actually remember if I did use them in the last game   

3 sparks are lighter than a terrier for nearly as much thrust, but not as good on fuel (but way better in an atmosphere).  I had a spreadsheet from my 1.05 playthrough where I'd worked out the lightest engine/tank options for a given payload, dV and TWR and worked out a load of curves like this (2000m/s and TWR>2).  

 

 

Annoyingly I can't find the spreadsheet now

 

[DarkHawkGames]

But how do you attach multiple engines to one fuel tank, though?

[bewing]

Some engines specifically attach radially, of course. For the rest, you can stick a couple little girders on the side of your fuel tank and put the extra engines on the bottom of the girders.

[RizzoTheRat]

15 hours ago, DarkHawkGames said:

But how do you attach multiple engines to one fuel tank, though?

I'd usually go for extra tanks with the engines attached, so for a lander you might have a central tank with one engine to get you home, and radial tanks with extra engines for landing and the first couple of km of takeoff.

I'm always surprised how many people like the Poodle for Mun/Minmus landers in the early game, you need a pretty big ship before you need that much thrust.  I prefer to go for the Colin Chapman approach... add lightness.

Edited May 10, 2016 by RizzoTheRat

[DarkHawkGames]

6 hours ago, RizzoTheRat said:

I'm always surprised how many people like the Poodle for Mun/Minmus landers in the early game, you need a pretty big ship before you need that much thrust.

It's mainly because there aren't small enough engines. It takes so long to get the smaller probe-sized engine/tanks which are the bread and butter of my unmanned missions

[JLE]

You could use a big retro rocket, but it is not quite efficient. That's why there are stages, less weight needs less fuel and you have less waste.

[Plusck]

Almost all of my landers have a docking port on the bottom, so they necessarily have two or more engines under radial tanks. For Mun or Minmus, two Sparks are more than enough for all my landers. Multiple Terriers only really become necessary for very large payloads, like the MPL or mining/fuelling craft.

Edited May 10, 2016 by Plusck