creating a universal lander

[creator1629]

hello, i was planning on designing a lander that could be used on all the planets and moons (except for jool of course) and was wondering what is the most delta v i would need for a landing? most moons have low gravity so that isn't generally going to be a problem, and for planets with stronger gravity they usually have an atmosphere which helps with aerobraking and parachutes. but the places with relatively strong gravity but without an atmosphere might be a challenge, so my question is, theoretically what is the most delta v i would need for a landing assuming i already have a stable orbit around my target?

[Reavermyst]

Theoretically, you can get that by finding the one planet with the highest Delta-v requirement and aim for that. So I suppose aiming for an Eve lander would make for a fairly universal set up.

So 12,000(11,500 according to the wiki) would be your Delta-v goal for a universal lander according to this chart! That is, if you plan on leaving Eve. Eve has the highest Gravity of all the planets(with a landable surface) at 5 times the gravity of Kerbin. landing would be hard enough, but leaving is a different story. Not impossible, just tough.

If that proves to be to high a budget for a reasonable lander, then about 4,000 Delta-v(Over Tylo, but under Kerbin) would be the next best thing!

Edited June 3, 2013 by Reavermyst

[tavert]

Are you trying to land multiple copies of the same design in a bunch of different places with no provision for return? Then you need a Tylo-capable lander with 2500-3000 m/s vacuum delta-V. If you'd also like it to get back to orbit, then you'll need at least another 2400 m/s, again for Tylo. And an Eve ascent vehicle is quite a bit larger than that, a very specialized design that's not worth hauling around anywhere else.

@Reavermyst: Eve's gravity at the surface is 1.7 g's. It's the atmosphere that gets to 5 times as thick as Kerbin's, at sea level. Landing at the highest mountains on Eve, around 6400 m altitude, can cut down the ascent to about 8500 m/s.

Edited June 3, 2013 by tavert

[creator1629]

oh sorry i should clarify, i just want to land on the target i dont need it to get back into orbit, as all im doing is depositing a small rover. cuz i think that 12,000 figure is for getting back into orbit around eve isn't it? landing there shouldn't require too much as it has a thick atmosphere and i can attach a few parachutes

[creator1629]

oh yes tavert, thanks, thats exactly what i meant. its just a probe rover im landing, and its not meant to come back at all. so im guessing tylo is the target with the highest gravity among the celestial bodies without an atmosphere?

[tavert]

Yes on both counts. If you really want the same design for everything, the parachutes just cost mass and delta-V on all the airless bodies. To do a powered landing on any body with a solid surface, you'll need a (Kerbin-relative) TWR higher than 1.7 for Eve and at least 2500 m/s delta-V for Tylo.

Edited June 3, 2013 by tavert

[creator1629]

yeah i have made many customized landers for different targets and i figured i would challenge myself by making a lander that could land on anything, then sending a whole bunch of them en masse around the solar system. for eve, that TWR requirement of 1.7, can that be offset by adding more parachutes?

[kahlzun]

I currently have three omni-landers. One rover, one probe, and one return-capable.

I'll provide photos, showing they are Tylo capable.

behold:

1. "Regent_IIb" the one-way colonising rover

The tanks are designed to eject once you have landed. The TWR of 0.66 is for Kerbin, Tylo only has 0.8 G, and this thing can easily land safely from a 100km orbit. The chute will land it safely on atmospheric bodies, it is recommended to eject the tanks for all atmo bodies except Duna.

2. "Science Probe XV" I never got around to naming this properly.

Note that the one shown is version XIV, the current one uses a T400 tank, and has sepratrons to allow tank ejection.

It's actually capable of a land-and-orbit-and-land-again on Duna.

3. "Soothsayer V" This one is manned (using the seats), and is return-capable from Eve, as well as Tylo.

Edited June 3, 2013 by kahlzun

[tavert]

yeah i have made many customized landers for different targets and i figured i would challenge myself by making a lander that could land on anything, then sending a whole bunch of them en masse around the solar system. for eve, that TWR requirement of 1.7, can that be offset by adding more parachutes?

Sure, I've done semipowered (chutes + engines) landings on Eve under parachutes with TWR less than 1.7 (relative to Kerbin, 1 relative to Eve). You use the engines at full throttle to reduce the effective force of gravity, but your drag coefficient doesn't change so your terminal velocity is slower. With enough parachutes you don't need the engines at all, but again, adding parachutes costs delta-V on airless bodies.

Having a high TWR helps a lot for Tylo though. You can see how kahlzun's first craft with the low TWR used a lot more delta-V to land. And remember you can reduce landing delta-V if you start from as low an orbit as possible. Here's my latest Tylo lander (which also gets back to orbit): http://imgur.com/a/NKaJU#0 uses 2573 m/s to land from 25 km orbit under MechJeb control, starting TWR is 1.24 relative to Kerbin, 1.55 relative to Tylo.

Edited June 3, 2013 by tavert

[Francesco]

tavert, I've seen quite a number of your ships using aircraft landing gear: I guess it's because they are weightless, allowing you to have more delta-v?

[tavert]

Yep, pretty much everything I've made has used them since I found out they're massless. They also can take harder landings than the struts. I'm taking advantage of it while it lasts, since it'll probably be fixed at some point.

[kahlzun]

That might explain why my planes keep spazzing out, in the SPH they're shown as 0.5T, and i tend to use them to balance my places a little..

[tavert]

Possibly. Believe the CoM indicator before you put the wheels on, not after.

[AndreyATGB]

I'd recommend using asparagus staging in your lander as well. There might be some debris from it if you mind that, but it's the most efficient way to do it. I haven't managed an Eve ascent yet, but my current lander has about 5500 dV without the rover attached (which is obviously left on the surface). It can't orbit Tylo after landing (got 800dV left) but the last stage of asparagus has 3700dV so it would be enough if I manage to refuel it somehow. Use some aerospikes and mix them with LT-V45's, you'll need some gimbaling.

[creator1629]

oh ok thanks a lot for the info guys. i have been able to design a 22 metric ton lander + rover, with 2956 m/s delta v, it has a kerbin TWR of 1.8, and is equipped with 4 XL parachutes, that should get me to any of the celestial bodies in the system. next step, design the tug to get this thing into the targets orbit