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JackBush

Never enough fuel ...

Question

I've been experimenting with ships with 2 and 3 Science Jrs in the pod that carries 3 scientists. (I always get rid of the pilot and engineer. I don't need them since I'm playing science mode (1.05)). And with ships that have almost no science or, in the case of the last one, none. No matter how simple I make them, I always end up getting into my lander fuel to complete my orbit and make the Hohman Transfer, etc. This of course leaves no fuel to get back. If I add more fuel and engines in stages, the same thing happens. It seems a vicious circle. And for those of you  who have been following my painful attempts to garner science from Mun, I must seem an idiot. I have no idea how people manage to get 3 Science labs up there and then hop around the biomes. Now and then I can get to one and bring back a few science points but nothing substantial. I despair.

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2 hours ago, Snark said:

Very nice and helpful screenshot!  Yes, you've got plenty of selection there, in both the 1.25m and 2.5m sizes.  Specifically, you have all the parts you need either for my booster or Laguna's.  You're good to go.

Absolutely, yes. It's that sweet spot that you reach in the game when you're able to do just about anything, from the very small to the very large (not yet enormous, but not far off it with the twin boar), except for efficient interplanetary stuff. It might be an idea to read up on asparagus staging and unlock that fuel line soon...

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3 hours ago, JackBush said:

Snark asked what I  had in the way of engines, I think. Here are my pod, fuel tank, and engine availabilities:

http://imgur.com/a/dmc3p

Thanks to everyone for being so generous with time and advice.

You're welcome!  

I'm still in my 1.04 Science Mode save, and actually did go to Minmus first for a big science-mining mission that unlocked the rest of the (stock) tech tree (did some earlier one-off landings there and on the Mun too as well as some probes to Eve and Duna, plus I science-mined the KSC).  I think I used an Apollo-style mothership-lander combo, refueled in orbit and then went back down for more science.  I think I had all the instruments by then, and went to every biome on Minmus (each of the flat areas is its own biome), and came back with something like 4000+ (or was it 6000?) Science.

Since you do have the Mainsail, you can use a better lifter:

jtUiJhe.png

This uses a Mainsail as the core engine, a Skipper and Rockomax-32 tank as the kick stage (enough to send it to the Mun or Minmus), plus two Skippers in the radial boosters.  Add two more of those boosters and you'll have over 9700 m/s total DV. :)  I didn't have KER when I was doing my Minmus/Mun missions, so I had no idea what my rockets were actually capable of--could have gone to Duna. :)

 

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5 hours ago, Plusck said:

Just for fun, I decided to recreate something with the same capabilities using the 3-man command pod.

  Reveal hidden contents

 

2UwOz1D.png

Although I hadn't noticed that there was a ladder on the original, so that's one mistake. You have to jet-pack off this one, while avoiding the solar panels.

So from 14.4 tons the total goes up to 44 tons. Although the thrust-to-weight ratio is listed at 0.58 (compared to the original's 2.6), that's because I didn't change the setting from Kerbin to the Mun, so it is actually higher (more like 3.5).

It isn't that much more expensive, but that's because the main cost of the lander itself comes from all the experiments it is carrying. The cost of the lifter to get it up to orbit, on the other hand, will be significant.

 

Very good, and here's a jumbo version with over 5300 m/s DV plus a lifter (using only 2.5m parts) to get it into orbit.

Spoiler

Z5sF67f.png

 

Spoiler

nzEzAih.png

The lifter is all Mainsails including the upper stage. Yeah, it could have been asparagus-staged, but I usually don't bother with that.  And it ought to have used the 3.75m parts, but JackBush doesn't have those yet. :)

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23 hours ago, JackBush said:

I've been experimenting with ships with 2 and 3 Science Jrs in the pod that carries 3 scientists. (I always get rid of the pilot and engineer. I don't need them since I'm playing science mode (1.05)). And with ships that have almost no science or, in the case of the last one, none. No matter how simple I make them, I always end up getting into my lander fuel to complete my orbit and make the Hohman Transfer, etc. This of course leaves no fuel to get back. If I add more fuel and engines in stages, the same thing happens. It seems a vicious circle. 

Others have already given advice on making your craft lighter, but there's also nothing wrong with having a larger craft if you want to go for a mission that more resembles real-life missions. When I do Mun landing missions, it is always with at least a 2-person crew, and I tend to use the lander-can, or even the inefficient the MK-2 pod. It should be entirely possible given your current tech-level.

While I haven't seen your initial designs, I think the biggest error I see newer players making is having a too-high TWR in space. Having an initial TWR of more than 0.5 (5m/s/s) in space is completely unnecessary. I usually start with around 0.3 for any longer mission.

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I have landed a science lab about 3 times ( different trips) and have gotten 5000+ of science each time, maybe even more. I easily could have gotten all the science I needed by just going to Minmus.

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On 1/14/2016 at 4:50 PM, JackBush said:

I always end up getting into my lander fuel to complete my orbit and make the Hohman Transfer, etc. This of course leaves no fuel to get back. If I add more fuel and engines in stages, the same thing happens. It seems a vicious circle.

Jack Bush,

 Judging by your description, it appears to me that your design process is backwards. If you take a failing design and try to add fuel and engines to fix it, you're only going to end up with a bigger design that doesn't work.

You need to plan out each stage from the end of the mission all the way back to the pad, and then design each stage so that it will meet it's requirements.

 More info here:

Good luck!

-Slashy

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Just to close this off: I made it to and home from Minmus safely today with a nice bunch of science points. And I have to thank Laguna for his/her designs which I brazenly and unashamedly copied. The lander design especially gave me lots of fuel at Minmus to get home. I didn't do a biome jump this time but think I will next trip.

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Congratulations!  

Hey, no prroblem, glad to help, and I called it a "standard design" because I thought that was what most people make first, but maybe it is more of a personal style.  Sure, you could just stick 3 or 4 landing legs on a single FL-T400 (or -200 or even a -100) tank with a Terrier or Spark engine and you have a lander, or go more minimalist with something like Snark's, but I like my landers wide and low and with plenty of fuel, which is why I use 4 radial tanks around a central one.  Sure, it's heavier, but more delta-V is better than less. :)

Now, when you get better, you can make something like this: :D

 

Spoiler

HByLHXn.png

 

Edited by Laguna

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