Modding engines / Is this too powerful for Eve?

[Benie]

Don't know how to pronounce the title, but I got a situation. I modded the Mark 55 Radial Mount Liquid Engine, to have 500 pounds of thrust. My Rover/Lander has 4 engines, which equals to 2000 pounds of thrust; 500 pounds more than one Mainsail. It also has a very high heat and damage tollerance This is to get my ship to leave Eve's atmosphere unharmed.

But, is it too powerful for Eve? You see, I use MechJeb's Landing Autopilot. And it didn't do the breaking burn like it has in the past, with this design, which is why I feel I made the engines more powerful than they need to be.

Here's a picture of my Rover/Lander, on the launchpad. Going by it, can someone help me out by balancing the right thrust to make MechJeb use its breaking burn again, yet also be able to escape Eve's crushing gravity?

And that's not all. When I tried to land on Kerbin, the chutes ripped off after it slowed to 100m/s. This has never, ever happened to me (even with this design), and it feels very discouraging. I'd like that not to happen again. And I think it happened because again, Landing Autopilot didn't do its breaking burn. I think of how powerful the engines are, it let physics slow it down, and had no need to use the engines.

[HoY]

It looks at the engine thrust (twr) and calculates exactly how long it will take to kill its vertical speed. You simply were just impatient and didn't wait to see what it would do 3 meters above the ground lol. Try it again and let it do its thing. This time don't use the chutes just let it be

[Benie]

I see. But are these engines too powerful for Eve? What should I tone them down to, like 175 to have like 700 pounds of thrust?

[painking]

Eve's atmosphere is thicker than Kerbin's and its gravity stronger. Landing via deceleration burns sounds kinda dangerous, not to mention a waste of fuel when there's all that cushiony air for your parachhutes to catch and slow you down. Strap some radial parachutes onto the radial engines cause I'm not sure if that one will slow your ship down enough.

Also anything that lands on Eve usually doesn't come back. Since Eve is just overall bigger than Kerbin, you need more TWR to lift equivalent weights back on Kerbin. So to get that rover off of Eve requires a bigger rocket than the one that took you onto the planet in the first place. Doesn't seem like those radials have enough fuel to get the job done anyway. Atmoshphere's a whole 20km higher than Kerbin's.

Edited July 15, 2013 by painking

[painking]

double post.

[Benie]

First off, fuel isn't a concern for me (note my title). The problem isn't the fact it's not slowing down enough. When I burn through the atmosphere, my lander slows down substantially.

It handled Eve better than I expected. With the chutes, my speed dropped to 3.4m/s.

And about the deceleration burn, it's what MechJeb's Landing Autopilot does. I've landed on Duna several times, no problems with it.

[Flixxbeatz]

There's no such thing as "too powerful" for Eve.

[Benie]

Yes, but I don't need to go overboard with the thrust and possibly rip my lander apart. There's got to be a balance.

[painking]

So yeah, your question has indeed been answered. Mechjeb knows when to burn and for how long, and while it's scary to watch your rocket plummet to its death while mechjeb does nothing, you gotta trust its math. Mechjeb also occasionally just decides not to work. Try turning the autopilot on and off to see if it changes anything. Also your lander isn't going to rip itself apart. If rocket tears itself apart from too much thrust, then you didn't put enough struts on it.

[ThePsuedoMonkey]

Based on your landing speed and number of parachutes I'm guessing that thing is about 6 tons, in which case a total of 216kN of thrust will give a TWR around 2 on Eve. Now if you just removed the engines from it, the parachutes would drop your landing speed under 3m/s anyway. As for the braking burn, terminal velocity on Eve is around 60m/s and 2000kN on a 6T ship means an acceleration of over 300, so a suicide burn would start 0.2s before crashing

[Cashen]

Eve's atmosphere is so thick you shouldn't need rockets for landing. Parachutes alone should do the trick if you have enough of them. Then just use some small solids to blow away the parachute mount stage (kind of like a skycrane) and drive away.