need help with moon lander

[keither1982]

I have been using real solar system with realism over haul and I am having severe problems making a moon Lander. I have all most 6k delta v set aside for landing and taking off from the moon and still can't do it. I want to know what is the most efficient way to land on the moon. Right now I am just lowering my orbit till it hits the ground and  slowing down till I am over my target then burning off all speed. I know I must be doing something wrong and I don't know what for the life of me.

[dafidge9898]

43 minutes ago, keither1982 said:

I have been using real solar system with realism over haul and I am having severe problems making a moon Lander. I have all most 6k delta v set aside for landing and taking off from the moon and still can't do it. I want to know what is the most efficient way to land on the moon. Right now I am just lowering my orbit till it hits the ground and  slowing down till I am over my target then burning off all speed. I know I must be doing something wrong and I don't know what for the life of me.

So you're in a low moon orbit with 6k dV? What's your TWR? The way I do it is I lower the periapsis to around 30km, then burn retrograde at periapsis and use pitch attitude to maintain a certain decent rate. 

[keither1982]

yes i burn into low earth orbit then lower my periapsis so that it shows a course that would hit the moon then i get as close as i think i can and burn off all speed. the moons gravity will speed me up after so i burn to cancel it out as needed untill i land. so you burn to 30k and slowly bleed off speed while maintaining your vertical speed. ? also my thrust to weight i think is around 3 i think i could lower it a lot more but my lander is all ready huge and dont think i should need the fuel i all ready have want to fix my mistake and use less fuel.

Edited August 2, 2016 by keither1982

[DD_bwest]

doesnt a low twr lander suffer more gravity losses than a higher one because of the time spent burning and fighting gravities accelleration?

 

i havent done rss in a while, maybe ill give that a new shot again.

[dafidge9898]

26 minutes ago, keither1982 said:

yes i burn into low earth orbit then lower my periapsis so that it shows a course that would hit the moon then i get as close as i think i can and burn off all speed. the moons gravity will speed me up after so i burn to cancel it out as needed untill i land. so you burn to 30k and slowly bleed off speed while maintaining your vertical speed. ? also my thrust to weight i think is around 3 i think i could lower it a lot more but my lander is all ready huge and dont think i should need the fuel i all ready have want to fix my mistake and use less fuel.

Yes, that's what I do. And a TWR of 3 is pretty good and should prevent huge gravity losses. If you post the craft file, I could take a look at it. 

[keither1982]

ok i just have to look up how to post craft files i am a newb to all this but i will when i figure it out

 

[dafidge9898]

6 minutes ago, keither1982 said:

ok i just have to look up how to post craft files i am a newb to all this but i will when i figure it out

 

Make a dropbox account, click upload, and select the file from your ksp folder/saves/ships/vab, then click share and create url

[keither1982]

ok sweet easy enough thanks for the help btw i will try to get to that tonight befor i go to bed and post it eather later tonight or tomorrow. again thanks this really has taken up all my free time this week lol   i am one of those people that will never stop till i get it right.

[keither1982]

OK this is the Lander and rocket I have been using. The only difference is this save is before I added rcs thrusters to one of the upper stages of the rocket and before I extended the tanks to the Lander to include more delta vs. 4200 vs. 6000 other then that this is what I have been working with. Like I said I am not sure what I am doing wrong best guess is I am landing wrong. Can how you land matter so much with delta v ?.

https://vadoons.sharefile.com/d-s24b85d8d00647ad8

[dafidge9898]

10 hours ago, keither1982 said:

OK this is the Lander and rocket I have been using. The only difference is this save is before I added rcs thrusters to one of the upper stages of the rocket and before I extended the tanks to the Lander to include more delta vs. 4200 vs. 6000 other then that this is what I have been working with. Like I said I am not sure what I am doing wrong best guess is I am landing wrong. Can how you land matter so much with delta v ?.

Your rocket does not look too efficient. There are a lot of improvements that can be made, but I digress. As for the lander, the most efficient descent with a TWR that high would be to lower the periapsis to around 30km. Then, at periapsis, completely kill horizontal speed and just fall straight down. Then, at the last second, burn. That way you'll be slow enough to land right above the surface. This is known as a "Suicide Burn", probably because you have to be borderline suicidal to carry it out.  This is the most efficient way for pretty much every lander, but most landers don't have a TWR of 4, making it more difficult (and dangerous) to do this. Now about adding dV to your lander, don't just add fuel. Try getting a smaller engine that weighs less, and don't have 8 really big RCS thrusters. Leave only the 4 quad thrusters, and switch them out for the smaller ones. Just changing your RCS thrusters to my suggested way increases your dV on the lander by 100. Configure the RCS so it uses the same fuel type as the engines, so you don't have to carry an extra fuel that you may not entirely use up. I take back what I said about the lander engine; it's a pretty efficient hypergolic engine. For your service module, or whatever you will have your lander dock to in space, it does not need three engines. It hardly needs 1 engine of that size. The Apollo CSM had an earth TWR of 0.3; yours is 1.05. 

About your RCS thrusters, you can configure their fuel type. If you configure their fuel type to MMH/NTO (which is what your lander/CSM engines currently use), you will not have to carry a very heavy hydrazine tank. I increased your lander dV by over 1000 by doing this. 

You only needed help with the lander, but your rocket also needs improvement. If you'd like any more tips, I'd be more than happy to assist.

Edited August 3, 2016 by dafidge9898
Being more polite

[keither1982]

16 hours ago, dafidge9898 said:

Your rocket does not look too efficient. There are a lot of improvements that can be made, but I digress. As for the lander, the most efficient descent with a TWR that high would be to lower the periapsis to around 30km. Then, at periapsis, completely kill horizontal speed and just fall straight down. Then, at the last second, burn. That way you'll be slow enough to land right above the surface. This is known as a "Suicide Burn", probably because you have to be borderline suicidal to carry it out.  This is the most efficient way for pretty much every lander, but most landers don't have a TWR of 4, making it more difficult (and dangerous) to do this. Now about adding dV to your lander, don't just add fuel. Try getting a smaller engine that weighs less, and don't have 8 really big RCS thrusters. Leave only the 4 quad thrusters, and switch them out for the smaller ones. Just changing your RCS thrusters to my suggested way increases your dV on the lander by 100. Configure the RCS so it uses the same fuel type as the engines, so you don't have to carry an extra fuel that you may not entirely use up. I take back what I said about the lander engine; it's a pretty efficient hypergolic engine. For your service module, or whatever you will have your lander dock to in space, it does not need three engines. It hardly needs 1 engine of that size. The Apollo CSM had an earth TWR of 0.3; yours is 1.05. 

About your RCS thrusters, you can configure their fuel type. If you configure their fuel type to MMH/NTO (which is what your lander/CSM engines currently use), you will not have to carry a very heavy hydrazine tank. I increased your lander dV by over 1000 by doing this. 

You only needed help with the lander, but your rocket also needs improvement. If you'd like any more tips, I'd be more than happy to assist.

Hay thanks for replying back. Yeah I love constructive criticism I will try and make some changes and tell you how it goes. I was wondering could you change the rocket and Lander and send me a link to the new one they maybe explain a little bit what you did and why. If you don't have the time that is fine just the tips you gave me have been great. Also if I remember correctly the first and second stage of the rocket were meant to be just shy of orbit by 2k delta v. The reason I did this is because I used the next stage to circularize the orbit and finish it up then. Then the stage after that was used for the burn to the moon. The final stage before the Lander its self was used to get into orbit make a inclination change to 0 degrees. The inclination change was to make it easier for the Lander to dock with it after taking off from the moon. When redocked I burned for a return home. I am sure my logic is flawed with my design but that is the idea of it.

[dafidge9898]

2 hours ago, keither1982 said:

I was wondering could you change the rocket and Lander and send me a link to the new one they maybe explain a little bit what you did and why.

I'd be happy to. I'll give you some tips on RSS moon landings along with the new craft (I have quite a few under my belt). Expect it within 24 hours.

[dafidge9898]

17 hours ago, keither1982 said:

Hay thanks for replying back

And now we have an updated rocket. Pic: http://imgur.com/a/3amPK

I replaced the decouplers between stages with fairings to make it more aerodynamic. I'm guessing you have the procedural fairings mod because I'm pretty sure it's an RO dependency. If not, get it. Also, get Ven's Stock Revamp. I kept the first stage pretty much the same because it was already pretty good. High mass fuel for the first stage is always a good choice.

The second stage comes complete with a new, RS-25 hydrolox engine; much more efficient that the previous pentaborane burning one. The TWR of the second stage and payload is now only .5, decreased from 1. This is ok, it just means you have to pitch up a little while it's burning. Most second stages, actually, have TWRs less than 1. Assuming your launch is mostly efficient, the first two stages should get you into orbit without having to burn the third stage. I changed the second stage fuel tank to balloon-cryo, making it extra lightweight. You can do this in the right click menu of the fuel tank in the VAB. The second stage also comes equipped with four RCS thrusters and four small spherical fuel tanks towards the bottom. The RCS thrusters burn Aerozine-50 and NTO. By the way, you can change the configuration of engines and RCS thrusters in their right click menu in the VAB, under engine GUI. Jettison the fairings at around 120 km.

The third stage engine is the same, but the fuel tank has been changed to balloon-cryo as well. This is your transfer stage, however if your launch is inefficient, there is extra fuel for you to circularize. The transfer stage also comes with four RCS thrusters. They also burn A50 and NTO.

The CSM and lander have the most changes. The CSM has only one engine now. It's the same engine, but there's only one of them. There are 4 RCS thrusters around it's CoM, reduced from 8. They burn the same fuel as the main engine does (I configured it in the Engine GUI mentioned above). I removed the heat shield and added a life support module. I reduced the mess of decouplers you had before. The lander has fewer RCS thrusters as well, and the same engine. Its RCS thrusters also use the same fuel as its engine. There are new, more powerful solar panels, and there are only two of them on each craft. I trashed the hydrazine tanks, reducing a lot of weight. It's a common beginner mistake to overload on RCS fuel. I've done it a lot in the past. 

After completing your transfer burn, you must stage and separate the spacecraft and lander from the transfer stage. Then you must stage again, and pilot the command module to dock with the lander right beneath it. Do it Apollo style, where the CSM turns around and docks with the lander. Do correction burns to place your moon periapsis around 80 km, then once you get there, burn to circularize. You have enough fuel to do this with your lander attached; it should spend about 800 dV. When you're ready, EVA the kerbal to the lander, and undock. Lower the lander periapsis to 30 km, and do the descent as I have described before. DO NOT try and change the inclination to 0; you will run out of fuel. Instead, land slightly west of your CSM's orbit; you have enough fuel for this. Once you've had enough time on the moon, do your ascent like any other and rendezvous  and dock with the CSM. EVA your kerbal to the CSM, then ditch the lander. Transfer back to Earth, and reenter. The Mk1 pod comes with 200 units of ablative material. Considering a LEO reentry only burns about 20 of the 200 ablative material, I think a reentry from the moon will be fine, but if you end up burning up, you should have enough dV to add a heat shield. 

I think that's it. 

Craft file: https://www.dropbox.com/s/5sjq8auq3mcz72u/moon express 1234 V2.craft?dl=0

Any questions?

Edited August 4, 2016 by dafidge9898
Picture didn't show

[keither1982]

48 minutes ago, dafidge9898 said:

And now we have an updated rocket. Pic: http://imgur.com/a/3amPK

I replaced the decouplers between stages with fairings to make it more aerodynamic. I'm guessing you have the procedural fairings mod because I'm pretty sure it's an RO dependency. If not, get it. Also, get Ven's Stock Revamp. I kept the first stage pretty much the same because it was already pretty good. High mass fuel for the first stage is always a good choice.

The second stage comes complete with a new, RS-25 hydrolox engine; much more efficient that the previous pentaborane burning one. The TWR of the second stage and payload is now only .5, decreased from 1. This is ok, it just means you have to pitch up a little while it's burning. Most second stages, actually, have TWRs less than 1. Assuming your launch is mostly efficient, the first two stages should get you into orbit without having to burn the third stage. I changed the second stage fuel tank to balloon-cryo, making it extra lightweight. You can do this in the right click menu of the fuel tank in the VAB. The second stage also comes equipped with four RCS thrusters and four small spherical fuel tanks towards the bottom. The RCS thrusters burn Aerozine-50 and NTO. By the way, you can change the configuration of engines and RCS thrusters in their right click menu in the VAB, under engine GUI. Jettison the fairings at around 120 km.

The third stage engine is the same, but the fuel tank has been changed to balloon-cryo as well. This is your transfer stage, however if your launch is inefficient, there is extra fuel for you to circularize. The transfer stage also comes with four RCS thrusters. They also burn A50 and NTO.

The CSM and lander have the most changes. The CSM has only one engine now. It's the same engine, but there's only one of them. There are 4 RCS thrusters around it's CoM, reduced from 8. They burn the same fuel as the main engine does (I configured it in the Engine GUI mentioned above). I removed the heat shield and added a life support module. I reduced the mess of decouplers you had before. The lander has fewer RCS thrusters as well, and the same engine. Its RCS thrusters also use the same fuel as its engine. There are new, more powerful solar panels, and there are only two of them on each craft. I trashed the hydrazine tanks, reducing a lot of weight. It's a common beginner mistake to overload on RCS fuel. I've done it a lot in the past. 

After completing your transfer burn, you must stage and separate the spacecraft and lander from the transfer stage. Then you must stage again, and pilot the command module to dock with the lander right beneath it. Do it Apollo style, where the CSM turns around and docks with the lander. Do correction burns to place your moon periapsis around 80 km, then once you get there, burn to circularize. You have enough fuel to do this with your lander attached; it should spend about 800 dV. When you're ready, EVA the kerbal to the lander, and undock. Lower the lander periapsis to 30 km, and do the descent as I have described before. DO NOT try and change the inclination to 0; you will run out of fuel. Instead, land slightly west of your CSM's orbit; you have enough fuel for this. Once you've had enough time on the moon, do your ascent like any other and rendezvous  and dock with the CSM. EVA your kerbal to the CSM, then ditch the lander. Transfer back to Earth, and reenter. The Mk1 pod comes with 200 units of ablative material. Considering a LEO reentry only burns about 20 of the 200 ablative material, I think a reentry from the moon will be fine, but if you end up burning up, you should have enough dV to add a heat shield. 

I think that's it. 

Craft file: https://www.dropbox.com/s/5sjq8auq3mcz72u/moon express 1234 V2.craft?dl=0

Any questions?

have not tryed it out yet but i will let you know when i do. i was wondering have you ever hade a issue with fairing shrinking soon as you click on them ?. my will shrink really small when i click on it and it will not let me make it larger.

[dafidge9898]

5 minutes ago, keither1982 said:

have not tryed it out yet but i will let you know when i do. i was wondering have you ever hade a issue with fairing shrinking soon as you click on them ?. my will shrink really small when i click on it and it will not let me make it larger.

I don't know what you mean. Some screenshots would help. Is it because when you click on the fairings, you detach them? 

[keither1982]

3 hours ago, dafidge9898 said:

And now we have an updated rocket. Pic: http://imgur.com/a/3amPK

I replaced the decouplers between stages with fairings to make it more aerodynamic. I'm guessing you have the procedural fairings mod because I'm pretty sure it's an RO dependency. If not, get it. Also, get Ven's Stock Revamp. I kept the first stage pretty much the same because it was already pretty good. High mass fuel for the first stage is always a good choice.

The second stage comes complete with a new, RS-25 hydrolox engine; much more efficient that the previous pentaborane burning one. The TWR of the second stage and payload is now only .5, decreased from 1. This is ok, it just means you have to pitch up a little while it's burning. Most second stages, actually, have TWRs less than 1. Assuming your launch is mostly efficient, the first two stages should get you into orbit without having to burn the third stage. I changed the second stage fuel tank to balloon-cryo, making it extra lightweight. You can do this in the right click menu of the fuel tank in the VAB. The second stage also comes equipped with four RCS thrusters and four small spherical fuel tanks towards the bottom. The RCS thrusters burn Aerozine-50 and NTO. By the way, you can change the configuration of engines and RCS thrusters in their right click menu in the VAB, under engine GUI. Jettison the fairings at around 120 km.

The third stage engine is the same, but the fuel tank has been changed to balloon-cryo as well. This is your transfer stage, however if your launch is inefficient, there is extra fuel for you to circularize. The transfer stage also comes with four RCS thrusters. They also burn A50 and NTO.

The CSM and lander have the most changes. The CSM has only one engine now. It's the same engine, but there's only one of them. There are 4 RCS thrusters around it's CoM, reduced from 8. They burn the same fuel as the main engine does (I configured it in the Engine GUI mentioned above). I removed the heat shield and added a life support module. I reduced the mess of decouplers you had before. The lander has fewer RCS thrusters as well, and the same engine. Its RCS thrusters also use the same fuel as its engine. There are new, more powerful solar panels, and there are only two of them on each craft. I trashed the hydrazine tanks, reducing a lot of weight. It's a common beginner mistake to overload on RCS fuel. I've done it a lot in the past. 

After completing your transfer burn, you must stage and separate the spacecraft and lander from the transfer stage. Then you must stage again, and pilot the command module to dock with the lander right beneath it. Do it Apollo style, where the CSM turns around and docks with the lander. Do correction burns to place your moon periapsis around 80 km, then once you get there, burn to circularize. You have enough fuel to do this with your lander attached; it should spend about 800 dV. When you're ready, EVA the kerbal to the lander, and undock. Lower the lander periapsis to 30 km, and do the descent as I have described before. DO NOT try and change the inclination to 0; you will run out of fuel. Instead, land slightly west of your CSM's orbit; you have enough fuel for this. Once you've had enough time on the moon, do your ascent like any other and rendezvous  and dock with the CSM. EVA your kerbal to the CSM, then ditch the lander. Transfer back to Earth, and reenter. The Mk1 pod comes with 200 units of ablative material. Considering a LEO reentry only burns about 20 of the 200 ablative material, I think a reentry from the moon will be fine, but if you end up burning up, you should have enough dV to add a heat shield. 

I think that's it. 

Craft file: https://www.dropbox.com/s/5sjq8auq3mcz72u/moon express 1234 V2.craft?dl=0

Any questions?

Ok i am having one problem th second stage seems to not have enough power to get into orbit. The time to ap comes and passes and i fall fall back to earth. I have been using mechjebs asent guidence nav ball marker to get the most efficent launch.

[dafidge9898]

1 minute ago, keither1982 said:

Ok i am having one problem th second stage seems to not have enough power to get into orbit. The time to ap comes and passes and i fall fall back to earth. I have been using mechjebs asent guidence nav ball marker to get the most efficent launch.

Are you changing the final angle to maintain altitude? Or are you letting the ship just stay level? 

[keither1982]

Just now, dafidge9898 said:

Are you changing the final angle to maintain altitude? Or are you letting the ship just stay level? 

so give it as much pitch as it needs to maintain ? i will try that

[keither1982]

19 minutes ago, keither1982 said:

so give it as much pitch as it needs to maintain ? i will try that

ok yeah that worked. Not used to geting into orbit like that but i can see were its a lot better opens up a lot of engine choices if you dont have to have a thrust to weight of 1.0

[keither1982]

On 8/4/2016 at 6:25 PM, keither1982 said:

ok yeah that worked. Not used to geting into orbit like that but i can see were its a lot better opens up a lot of engine choices if you dont have to have a thrust to weight of 1.0

I ended up having to change one of the engines and solar panels because I have not unlocked them in the tech tree. I used as similar items as I could find and that worked. The problem I have is when the Lander separate from the return vehicle it sends the return vehicle into a slight spin because of the force of separation. At first I tried adding more rcs thrusters thinking if I was faster it would be easier to dock with the moving docking port. Then I put a prob core on it and switched craft and made it so the docking port was stationary. I was wondering what would you do to stop the movement or is what I did just fine. 

Edited August 6, 2016 by keither1982

[dafidge9898]

On 8/5/2016 at 5:21 PM, keither1982 said:

I ended up having to change one of the engines and solar panels because I have not unlocked them in the tech tree. I used as similar items as I could find and that worked. The problem I have is when the Lander separate from the return vehicle it sends the return vehicle into a slight spin because of the force of separation. At first I tried adding more rcs thrusters thinking if I was faster it would be easier to dock with the moving docking port. Then I put a prob core on it and switched craft and made it so the docking port was stationary. I was wondering what would you do to stop the movement or is what I did just fine. 

Yeah, that's a good idea. It's always a good idea to have both modules controllable even if there's no pilot in them.