Building a long range miner rover carrying SSTO - tips wanted regarding efficiency

[mystik]

Hi all,

 

Having spent the past days reading on aerodynamics and stuff I started to build a large SSTO capable for planet hopping. What I have done is started with the Midgard B16M by Korsakovski. Thank you for the base vehicle. The model is available here: https://kerbalx.com/Korsakovski/Midgard-B16M

I chose this one because I see it is fairly large and has most of the setup already made and is very well designed. That being said, I have made modifications and looking for additional ideas and help.

 

What I changed:

- Removed all but one passenger cabin to convert to cargo holding and science;

- Replaced the front docking port with the claw for more utility;

- Replaced the Ramp intakes with shock cones (previously the engines would cut out when all were started, now the flameout is no longer present, have not tested high speeds);

- Added extra drill (raising the total number to 3);

- Added science cargo and 5 large reaction wheels for extra maneuverability and 5 large batteries;

 

What I want to ask:

The ship comes with two large ore tanks. I was wondering if it would be better to exchange them for small ore tanks since I am not interested in doing ore transports;

I'm looking to replace the end with a cargo loading bay for rovers. Should I attach rovers with a docking port? Is it possible to attach a rover using two docking ports at the same time (one forward and one underneath)?

What would you recommend as max electric charge to store? 5000? 10000? At which point is storing extra electric charge becomes useless?

 

That's it for now. I will get back with additional questions as I continue work. Thank you for any help.

 

Edit 9.01.2017, finally added the design, sorry for the delay

http://kerbalx.com/mystik/Thoth-III

Edited January 9, 2017 by mystik

[bewing]

51 minutes ago, mystik said:

What I changed:

- Removed all but one passenger cabin to convert to cargo holding and science;

Good.

51 minutes ago, mystik said:

- Replaced the front docking port with the claw for more utility;

Very wise.

51 minutes ago, mystik said:

- Replaced the Ramp intakes with shock cones (previously the engines would cut out when all were started, now the flameout is no longer present, have not tested high speeds);

Very wise. The shock cones have less drag and give more air.

51 minutes ago, mystik said:

- Added extra drill (raising the total number to 3);

In a practical sense, this probably won't help. You are probably going to want to timewarp through the ore extraction/conversion part anyway. It will take a large amount of realtime.

51 minutes ago, mystik said:

- Added science cargo and 5 large reaction wheels for extra maneuverability and 5 large batteries;

Good on the science. Can't hurt on the batteries and reaction wheels.

51 minutes ago, mystik said:

 

What I want to ask:

The ship comes with two large ore tanks. I was wondering if it would be better to exchange them for small ore tanks since I am not interested in doing ore transports;

Yes. You will want to keep the converter running while you drill, so it won't help anything to have large amounts of ore storage. You only need a little ore storage, and reducing mass is still important. But SSTOs are built to be carefully balanced around the CoM, so once you make all these changes, you may need to tweak some things to make it flyable again.

51 minutes ago, mystik said:

I'm looking to replace the end with a cargo loading bay for rovers. Should I attach rovers with a docking port? Is it possible to attach a rover using two docking ports at the same time (one forward and one underneath)?

Works just fine if you build it so that the docking ports are placed with perfect precision.

51 minutes ago, mystik said:

What would you recommend as max electric charge to store? 5000? 10000? At which point is storing extra electric charge becomes useless?

Probably only a couple thousand. It is much much much more important to have EC generators than EC storage. There is no way in stock that you can power drills and a converter through more than a few minutes of darkness.

[mystik]

4 minutes ago, bewing said:

In a practical sense, this probably won't help. You are probably going to want to timewarp through the ore extraction/conversion part anyway. It will take a large amount of realtime.

Thank you for the feedback. Should I stick to 2 drills instead? I imagined that more drills decrease extraction time. 2 by 50% and 3 by 66%. Is this not the case?

[bewing]

1 hour ago, mystik said:

Thank you for the feedback. Should I stick to 2 drills instead? I imagined that more drills decrease extraction time. 2 by 50% and 3 by 66%. Is this not the case?

In realtime, yes, that's the case. All I'm saying is that A) the ssto is already balanced for two, B) with one drill and fast timewarping, it takes 5 seconds, with two drills and slightly slower timewarping it takes 5 seconds, and with 3 drills and slightly slower timewarping, it takes 5 seconds.

You're going to be judging by when your fuel tanks are full -- not by watching the drills.

 

[Aegolius13]

1 hour ago, bewing said:

There is no way in stock that you can power drills and a converter through more than a few minutes of darkness.

If you don't mind playing a little fast and loose with thermodynamics*, you can bring a couple fuel cell arrays, and use a small portion of the LFO you're mining to generate electricity to power the mining equipment.  This does allow you to work at night (or in places with very weak solar energy), and also means you wouldn't need much battery storage.  Just remember to keep some oxidizer on hand - I tend to forget to leave some in LF-heavy spaceplanes. 

*[unless some chemical energy in "ore" is being utilized in the extraction process, on top of the 100% mass recovery you get with the 2.5m ISRU]

 

1 hour ago, mystik said:

Thank you for the feedback. Should I stick to 2 drills instead? I imagined that more drills decrease extraction time. 2 by 50% and 3 by 66%. Is this not the case?

That's correct, at least until you either exceed your radiator capacity and overheat, or bottleneck the ISRU.  The latter depends on ore concentration and engineer skill level, but is unlikely to be an issue until you have at least 4 big drills, unless you're mining an asteroid.  However, it really does not take that long to refill with 1-2 big drills, so the extra mass may not be worth it.  

It's pretty arbitrary, but I like to use 4 big drills in Mun/Minmus based mining rigs, 2 big drills on most interplanetary stuff, and 2 small drills on asteroid miners.  All paired with one 2.5m ISRU.

[Wanderfound]

4 hours ago, mystik said:

What I want to ask:

The ship comes with two large ore tanks. I was wondering if it would be better to exchange them for small ore tanks since I am not interested in doing ore transports;

I'm looking to replace the end with a cargo loading bay for rovers. Should I attach rovers with a docking port? Is it possible to attach a rover using two docking ports at the same time (one forward and one underneath)?

What would you recommend as max electric charge to store? 5000? 10000? At which point is storing extra electric charge becomes useless?

 

Answering in reverse order:

1) Thinks about generation rather than storage. You need enough power to run everything that you'll want to run at the same time (ISRU & drills, mostly). Unless you feel like covering the surface in a hundred solar panels, this will probably mean fuel cell arrays. As these have a substantial storage capacity themselves, extra batteries are usually unnecessary.

2) One belly or roof mounted port on a rover is usually enough to stabilise it. But: rovers are useless. If you're taking a spaceplane, you already have a wheeled vehicle in place. Just taxi around on the surface to get where you need to.

3) Keep in mind that an ore tank doubles as a universal fuel tank: i.e. you can take off with it full of ore, then convert it to fuel once you've cleared some space in the normal tanks.

 

SSTA mining demonstrator:

 

Rover attachment demonstrator:

http://m.imgur.com/gallery/sg45D

Edited December 29, 2016 by Wanderfound

[mystik]

Awesome, so I will reduce the drills to 2 and will keep note of the examples posted, should help reduce the weight and part numbers on the ship.

[mystik]

Hit a wall. Unfortunately the plane seems to shift left gently and I went and checked all parts to make sure everything is aligned. I have no idea what could be causing it. I only place things with snap activated and symmetry. I see these planes that go straight as an arrow but when ever I make something it always ends up drifting sideways.

[tseitsei89]

35 minutes ago, mystik said:

Hit a wall. Unfortunately the plane seems to shift left gently and I went and checked all parts to make sure everything is aligned. I have no idea what could be causing it. I only place things with snap activated and symmetry. I see these planes that go straight as an arrow but when ever I make something it always ends up drifting sideways.

Screenshots would be helpful but it sounds like you need a bigger tailfin to increase yaw stability

[mystik]

On 29/12/2016 at 6:17 PM, tseitsei89 said:

Screenshots would be helpful but it sounds like you need a bigger tailfin to increase yaw stability

Hi,

 

Sorry for not getting back sooner, I had a fever the past week and didn't feel like working on it too much. I have modified the plane more and reseated parts and now it goes straight. I do get some left yaw when pulling upwards, so I will take a look at the control surfaces to see what's wrong.

 

I am almost done with the design, but now that I look at it, I wonder how this will actually work. I mean, Taking off and landing on Kerbin is fine, even if the actual stopping is difficult. I have added two parachutes and 6 AIRBRAKES to help slowing down, as well as increasing the braking strength to 200 on all wheels. It does stop well enough without crashing as it lands at about 100m/s but it takes a while. I have not tested the parachutes yet so I am hoping this will help stopping.

 

But my real question is how do you land such a thing on a planet with no atmosphere? I worry that I won't be able to slow down a 250 tonne plane with only 4 atomic engines to land. I don't know what else to do to lose weight but the following options remain:

 

- clip like crazy to reduce the length of the cargo bays and maybe save 3 tonnes (but I don't like this idea too much)

- use only one science instrument instead of two (but that seems a waste since they are so light and creates a convenience to have some of them double in case you pass through two areas in flight and have not collected the science already).

- use the small ISRU, but I wonder, if this is a good idea, because while I would lose 2.75 tonnes, I wonder how much efficiency I lose as well.

- reducing the large radiator to a smaller one since the ISRU and drills no longer produce as much heat and saving 0.75 tonnes, but I wonder what happens if I try to land on Moho and start mining to refuel, would that create overheating.

- use only one large drill instead of two, not interested in using the small one since it won't touch the ground and is very bad to mine where resources are below a certain level, saving an extra 1.25 tonnes.

- replace the small holding tank with one small radial tank for the ore, saving another 0.37 tonnes, because I am not interested in storing ore, just converting it.

- remove one fuel cell, saving another 0.24 tonnes, since the small ISRU and single drill only require about 45 energy to work and with 3 I can generate about 54, plus I can plug in the rover for extra power needs if I want to transmit a lot of data or keep lights on around the ship during night.

- reduce the amount of doubled science instruments, batteries on the rover I carry and the amount of RTGs, completely dropping the solar panels and only use my front wheels for driving and disabling the back wheels so that less energy is required, even though the weight saving is small for the plane, it does make the rover light as well.

- reducing all the above means I can drop some control surfaces as well, improving aero and looking more weight, meaning less needed fuel or more delta V remaining.

- less weight means I can carry less RCS and that means I can use about 500 units instead of the big 1000 unit I have now, saving another 2.41 tonnes by dropping the mk3 tank for two R25 internal tanks (should give me a total 600 units with the mk3 cockpit).

 

As you can see reducing some weight usually means you can reduce more supporting weight. I wish I could bring it under 200 tonnes full but I doubt I can shave that much weight from a design. I will post some pictures so that people can understand better what I am making. With the savings above I can shave about 10 tonnes, without counting the removal of the additional control surfaces, which means less fuel needed.

 

I would like to know your opinion about the items, if it is worth it or not to change those things, or if it is just better to add more engines instead. Sorry for providing so much info and asking so many questions. I am struggling with efficiency but I want to make a ship that can travel almost everywhere instead of constantly wasting time returning and launching new rockets. Anyways, thank you for your help so far. Promise to post pictures soon, still wanting to tweak more before I submit it to analysis and review.

Edited January 5, 2017 by mystik

[Palaceviking]

250t on 4 nukes does sound a bit scary tho!

The rest sounds pretty bang on.

[Sharpy]

re: radiators. Smartly placed static radiators are way more mass-efficient. The advantage of extendable radiators is that they can be placed anywhere.

If you go with fuel cells, make sure you have a good engineer. With three-star you'll be barely breaking even on ore production / fuel consumption.

Airbrakes aren't really helpful on SSTO. They will be mostly useless at descent, when they are really needed, due to lousy thermal durability. They will be mostly useless at landing, being way weak at such speeds. They are good at supersonic speeds, but why if you can just throttle down, make a circle, take more time on descent?

Parachutes are very good as an addition to brakes after touchdown. Set rear brakes high, front brakes low, to keep your craft from turning and flipping. Or just screw it and land vertically on parachutes. Landing gear can take quite a bit of an impact, test how much you need not to break anything.

Consider dumping monoprop entirely and going with Vernors. Usually, either I run out of monoprop while still having fuel tanks full, or I land carrying 3/4 of monoprop supply with nearly empty fuel tanks. Having engines and RCS run on one resource is helpful, and the craft looks big enough that it would benefit from good, strong RCS. This also means you might consider dumping some reaction wheels - when you can turn slowly, you do it on the RWs. You need better torque - Vernors.

 

[mystik]

1 hour ago, Palaceviking said:

250t on 4 nukes does sound a bit scary tho!

The rest sounds pretty bang on.

You mean the TWR is not good enough, right? I wish I had a table to understand how much weight is recommended for one engine. I can add a few more engines to balance stuff out but I don't want to overdo it. The nukes are for interplanetary travel mostly as I plan to save some fuel for the engines to do quick slowdown burns while landing. I know you can calculate TWR and stuff but it would help to have some fixed values.

1 hour ago, Sharpy said:

re: radiators. Smartly placed static radiators are way more mass-efficient. The advantage of extendable radiators is that they can be placed anywhere.

If you go with fuel cells, make sure you have a good engineer. With three-star you'll be barely breaking even on ore production / fuel consumption.

Airbrakes aren't really helpful on SSTO. They will be mostly useless at descent, when they are really needed, due to lousy thermal durability. They will be mostly useless at landing, being way weak at such speeds. They are good at supersonic speeds, but why if you can just throttle down, make a circle, take more time on descent?

Parachutes are very good as an addition to brakes after touchdown. Set rear brakes high, front brakes low, to keep your craft from turning and flipping. Or just screw it and land vertically on parachutes. Landing gear can take quite a bit of an impact, test how much you need not to break anything.

Consider dumping monoprop entirely and going with Vernors. Usually, either I run out of monoprop while still having fuel tanks full, or I land carrying 3/4 of monoprop supply with nearly empty fuel tanks. Having engines and RCS run on one resource is helpful, and the craft looks big enough that it would benefit from good, strong RCS. This also means you might consider dumping some reaction wheels - when you can turn slowly, you do it on the RWs. You need better torque - Vernors.

 

Very useful reply. I am not sure about vernors as I have never used them. I see what you mean, and adding these should allow me to drop RCS completely, getting rid of the RCS thrusters and replacing them with a few of these as they have higher power for movement and stuff. That would mean 2.5 tonnes shaved and less control parts. I like the idea and will look into it. I would however like to add a small tank with crossfeed disabled for emergency usage only (these engines and for ISRU). In case I mess up and really need to use them. I would like to have about 2 minutes of full control without stopping so I will do some math and see how much fuel I need for this to work.

I currently run with 5 reaction wheels but I think it can run with 3 just fine. That shaves some weight as well and reduces the need for cargo space. This may also make the whole thing smaller.

No sure about the radiators. I think the current config is better than fixed radiators but I will look into this. Definitely fixed ones are more durable.

I do plan on taking the engineer with me, but how stupid would it be to drop the large ISRU and go with the small one, is it going to make things unbearable slow and inefficient?

AIRBRAKES are only used for slowing down when in the atmosphere. If you think these are useless I can give them up and add more parachutes for stopping faster after landed. I added them to help me not miss the runway when returning.

 

Thank you for your answers.

Edited January 5, 2017 by mystik

[Palaceviking]

Twr is thrust over mass times gravity so if you've got it down to 200tonnes then your kerbin twr is 0.12!! (somebody check my math) which limits you to minmus, gilly,pol and I think bop.

Just thought, what's your dry mass cos ssto's are mostly fuel usually. 

For example if your down to 105 ton when approaching to land then your twr would be 0.23( the bare minimum for mun).

Edited January 5, 2017 by Palaceviking
Fuel

[Sharpy]

44 minutes ago, mystik said:

. I would however like to add a small tank with crossfeed disabled for emergency usage only (these engines and for ISRU).

That's ok - usually if you run out of fuel "far out", RCS won't make any difference. But being able to dock to an emergency rescue vessel is valuable.

Don't forget they require oxidizer! I happened to make that mistake on jet+nuke craft that didn't need oxidizer for anything else

Spoiler

No sure about the radiators. I think the current config is better than fixed radiators but I will look into this. Definitely fixed ones are more durable

I'm not sure about mass, but the "blade" fixed radiators have a very nice form factor too. Fitting a bunch of them is easy and you can attach stuff to them (don't attach the drills though... through some odd quirk they don't cool drills directly attached to them.)

Quote

I do plan on taking the engineer with me, but how stupid would it be to drop the large ISRU and go with the small one, is it going to make things unbearable slow and inefficient?

If you plan to mine asteroids, very stupid. If you go to planets - only very moderately so. I made a Moho biome hopper with small ISRU; it would take about 40 in-game days to refuel about one long MK3 tank on two small drills, small ISRU and a three-star engineer. The same thing takes less than one in-game day on large drills and large ISRU - but if you don't mind stopping for a month, why not?

Quote

AIRBRAKES are only used for slowing down when in the atmosphere. If you think these are useless I can give them up and add more parachutes for stopping faster after landed. I added them to help me not miss the runway when returning.

For a large craft like this, they are pretty much useless. On descent from suborbital speed, they will pop like popcorn, making no difference. For slowing down before the runway, just throttle down far enough, or make a few turns. For slowing down ON the runway, parachutes are way better. And for slowing down ABOVE the runway - airbrakes will stall you and you will crash. Maintain your speed on descent and touchdown and only begin braking then.

They are good thing for agile, maneuvrable aircraft - fighters and such. They are marginally useful for big, bulky craft like yours though. They used to be awesome for use on reentry, but they underwent a massive thermal durability nerf, and while through some smart angling, heat management, strategical closing and opening them, you can still manage to use them, it's much easier to open a cargo bay or a service bay, which will slow you down ten times better.

[mystik]

 

1 hour ago, Palaceviking said:

Twr is thrust over mass times gravity so if you've got it down to 200tonnes then your kerbin twr is 0.12!! (somebody check my math) which limits you to minmus, gilly,pol and I think bop.

Just thought, what's your dry mass cos ssto's are mostly fuel usually. 

For example if your down to 105 ton when approaching to land then your twr would be 0.23( the bare minimum for mun).

That's scary indeed. Looks like my ship is terribly inefficient at landing. Would I be better off with two poodles instead? I can find the place for it and manage somehow to make it work if this proves to be a better choice. Plus, I remove 12 tonnes and add only 3.5 and that saves a lot of weight. Burn times would decrease also and get responsive maneuvers, plus increased maneuverability. I know there is a downside too: I have to replace the liquid fuel with liquid fuel and oxidizer. I don't mind it as long as this allows me to planet hop without becoming stranded.

 

How do you know that 0.23 is the minimum for the Mun? How do you do the math for this? I would like to know so that I can make a table and see if my ship meets the requirements for certain planets and can better plan landings and not do dumb things like descend and run out of fuel during that.

1 hour ago, Sharpy said:

That's ok - usually if you run out of fuel "far out", RCS won't make any difference. But being able to dock to an emergency rescue vessel is valuable.

Don't forget they require oxidizer! I happened to make that mistake on jet+nuke craft that didn't need oxidizer for anything else

  Hide contents

No sure about the radiators. I think the current config is better than fixed radiators but I will look into this. Definitely fixed ones are more durable

I'm not sure about mass, but the "blade" fixed radiators have a very nice form factor too. Fitting a bunch of them is easy and you can attach stuff to them (don't attach the drills though... through some odd quirk they don't cool drills directly attached to them.)

If you plan to mine asteroids, very stupid. If you go to planets - only very moderately so. I made a Moho biome hopper with small ISRU; it would take about 40 in-game days to refuel about one long MK3 tank on two small drills, small ISRU and a three-star engineer. The same thing takes less than one in-game day on large drills and large ISRU - but if you don't mind stopping for a month, why not?

For a large craft like this, they are pretty much useless. On descent from suborbital speed, they will pop like popcorn, making no difference. For slowing down before the runway, just throttle down far enough, or make a few turns. For slowing down ON the runway, parachutes are way better. And for slowing down ABOVE the runway - airbrakes will stall you and you will crash. Maintain your speed on descent and touchdown and only begin braking then.

They are good thing for agile, maneuvrable aircraft - fighters and such. They are marginally useful for big, bulky craft like yours though. They used to be awesome for use on reentry, but they underwent a massive thermal durability nerf, and while through some smart angling, heat management, strategical closing and opening them, you can still manage to use them, it's much easier to open a cargo bay or a service bay, which will slow you down ten times better.

If I scrap the nuclear engines like I said above I could ensure I have equal fuel for everything and save some weight but have less fuel.

What do you mean by the blade radiator? Is it the edge kind that sticks out perpendicularly if you mount them on the outside? I can see how to clip that inside the hull if that's better.

I don't plan on mining asteroids as this will be strictly for planetary travel and the refueling is only for the purpose of fueling itself and nothing else. That being said, I have no interest in spending 40 days per huge tank to refuel. I carry a lot of fuel and by your math that may take more than 150 days to refuel. That is too long. I can spend a few days on the planet then go. I want to be able to regularly tour the system and require little maintenance.

I will replace the AIRBRAKES then, sounds like it's pointless to have any, and open all my 3 cargo bays to see if that helps with slowing down.

Sounds like the large ISRU has to stay, and that thing is so heavy. Was hoping to save some space and weight. Maybe I can squeeze the rear cargo bay a bit to move the rover further back without clipping out. The thing is, I wanted my ship to be able to do full orbital surveys and as such I have included the M700 scanner attached to the back of the rover, which I intend to deploy once near a planet so perform the scan and then retract once I have the data. I am wondering if it's not better to just send out satellites to each body and forget about the extra scanner on board. I have a very good satellite model that has all the science on it and very light, able to travel and return from just about anywhere on it's own with the use of ion engines. Is carrying the M700 useless and should just launch satellites before I start missions to have them on site before I get there? They are also relay sats and will help with comms so once the science is done they remain relevant.

Reading my reply makes it clear to me that I should scrap the M700 and maybe the Narrow band one as well since it's better to do it via sat.

Edited January 5, 2017 by mystik

[Palaceviking]

Acceleration due to gravity on kerbin surface is the same as earth(9.8m/s sqrd), sometimes referred to as 1 g, mun like the moon has 0.23 g(ish) so this is the minimum force you would need to reduce vertical velocity when on a sub-orbital trajectory (it's pulling you down with 0.23(ish)g so you gotta push back)

The poodle has an isp of 350, the lvn 800, so work out your delta v either way, however each poodle packs 250kn of thrust, 10 more than 4 nukes!

I know this is problems on problems but better looked at now than when the surface of mun gets over friendly with your spaceplane

Two poodles under 200tonnes gives you a 0.25 twr which will improve as you burn off fuel, as your unlikely to weigh 200tonnes when you reach the mun it will probably be even better!

If you can squeeze enough deltav out of it I'd go two poodles. talking of which what  do you think dry/wet mass will be when you reach orbit?

Edited January 5, 2017 by Palaceviking
Poodles and poodles!!!!

[bewing]

32 minutes ago, mystik said:

How do you know that 0.23 is the minimum for the Mun? How do you do the math for this?

 

It comes directly from the definition of TWR, and the surface gravity of the Mun.

If your thrust is equal to your Kerbin weight, and you go to full thrust on Kerbin, you will hover. You won't go anywhere. And your TWR will be 1.

The Mun has a gravity that is 1/6 of Kerbin's. So a TWR of .166 on Kerbin means that full thrust on your engines on the Mun will make you hover, but not go up. .21 is just a little over (33% higher than) .166, so it's just enough of an edge to make things work on the Mun (or Ike or Dres). And this basically assumes landing on your tail, with your engines blazing.

 

[Sharpy]

42 minutes ago, mystik said:

If I scrap the nuclear engines like I said above I could ensure I have equal fuel for everything and save some weight but have less fuel.

What do you mean by the blade radiator? Is it the edge kind that sticks out perpendicularly if you mount them on the outside? I can see how to clip that inside the hull if that's better.

I don't plan on mining asteroids as this will be strictly for planetary travel and the refueling is only for the purpose of fueling itself and nothing else. That being said, I have no interest in spending 40 days per huge tank to refuel. I carry a lot of fuel and by your math that may take more than 150 days to refuel. That is too long. I can spend a few days on the planet then go. I want to be able to regularly tour the system and require little maintenance.

I will replace the AIRBRAKES then, sounds like it's pointless to have any, and open all my 3 cargo bays to see if that helps with slowing down.

Sounds like the large ISRU has to stay, and that thing is so heavy. Was hoping to save some space and weight. Maybe I can squeeze the rear cargo bay a bit to move the rover further back without clipping out. The thing is, I wanted my ship to be able to do full orbital surveys and as such I have included the M700 scanner attached to the back of the rover, which I intend to deploy once near a planet so perform the scan and then retract once I have the data. I am wondering if it's not better to just send out satellites to each body and forget about the extra scanner on board. I have a very good satellite model that has all the science on it and very light, able to travel and return from just about anywhere on it's own with the use of ion engines. Is carrying the M700 useless and should just launch satellites before I start missions to have them on site before I get there? They are also relay sats and will help with comms so once the science is done they remain relevant.

Reading my reply makes it clear to me that I should scrap the M700 and maybe the Narrow band one as well since it's better to do it via sat.

Consider a combo of Vector + Nuke. My Moho lander had this combo and it worked pretty great: lose most of speed, keep slowing down using nukes, then perform a few seconds of burn with Vector just to get the excessive descent speed reduced. Perform departure burn on both (must be precise), insertion burn on nuke alone (lots of time, lots of delta-V, can be very imprecise.

I like to put an array of the blade radiators in cargo bays - or just put a couple and use them as structure for other stuff - walkways for kerbals, mounts for science, radial tanks, etc. One of tenets of efficient design is to use parts for more than they were designed for. If I can replace structural parts with active ones, great!

One thing more.

Try how it goes if you dump landing gear and install powered ruggedized wheels. Then, if the effects are promising, dump the rovers

[Palaceviking]

Just now, bewing said:

It comes directly from the definition of TWR, and the surface gravity of the Mun.

If your thrust is equal to your Kerbin weight, and you go to full thrust on Kerbin, you will hover. You won't go anywhere. And your TWR will be 1.

The Mun has a gravity that is 1/6 of Kerbin's. So a TWR of .166 on Kerbin means that full thrust on your engines on the Mun will make you hover, but not go up. .21 is just a little over (33% higher than) .166, so it's just enough of an edge to make things work on the Mun (or Ike or Dres). And this basically assumes landing on your tail, with your engines blazing.

 

Or the absolutely crazy slow down on your brakes approach flying backwards for when your twr is just too low

See.youtube- one tank to tylo surface and back,  awesome but you won't see me doing it anytime soon

[mystik]

39 minutes ago, Palaceviking said:

Acceleration due to gravity on kerbin surface is the same as earth(9.8m/s sqrd), sometimes referred to as 1 g, mun like the moon has 0.23 g(ish) so this is the minimum force you would need to reduce vertical velocity when on a sub-orbital trajectory (it's pulling you down with 0.23(ish)g so you gotta push back)

The poodle has an isp of 350, the lvn 800, so work out your delta v either way, however each poodle packs 250kn of thrust, 10 more than 4 nukes!

I know this is problems on problems but better looked at now than when the surface of mun gets over friendly with your spaceplane

I see. I thought you meant the g but I wasn't sure because on the wiki it says that the Moon has 0.166g. To work out a comfortable descent profile I'd say twice of this value would guarantee not to flatten on the surface.

Edited January 5, 2017 by mystik

[Palaceviking]

 hm

Yeah sorry I've not mathed for while now, been lucky i guess

[mystik]

Very informative replies. I mean, I should already know all this stuff already, but my mind can't math well when I first look at a problem. After I receive a small boost things start to spin and then before you know it I get these elaborate excels and graphs and colors and I go to bed late smelling like math.

[mystik]

Converted it from a liquid fuel to a rocket fuel setup. The weight is now 300t full. Lost about 50% of total delta V but it's important it gets places rather than flying and not being able to slow down enough on descents. Now it has 10000 m/s instead of 15000 m/s. However, space wise should be about 6000 m/s which should be enough for planet hopping, but I have not yet performed the flight to Minmus to refuel.

 

2 Poodles and 12 Rapiers barely have enough for orbit. End up using half my liquid fuel and I run out of it while still having 60% oxidizer left. So, not wanting to increase the number of engines to save weight, I think I should start with 50% less oxidizer. This will make it easier to take off which should mean I don't need to add extra engines. All the other planets have less gravity than Kerbin, except for Tylo and Eve, which require special ships, and by that I mean rockets. I also only use 2 delta wings and small control surfaces to keep drag and weight down. Tanking off is a challenge since the ship wants to drop badly, but it does fly if you throttle to max, hit the brakes, wait until you reach 90kn and then release. At the end of the runway pull hard and it should barely go up, avoiding the ground barely with the rear engines. It's very tricky and I crashed it many times before I could get it flying. Hoping that with less fuel on board it should be able to do this much better. I tried with a canard but I think it actually causes more drag and problems than helps flight so I ended up disabling it in flight and the drag improved considerably. I will remove it later.

 

I will test this a bit then post the craft here along with the files for it so that you can give it a go and tell me what you think. Sorry for the long delay, I always start the game and say I will post something then I get into building it and hours fly testing and I forget.

[Palaceviking]

Maybe you should try avoiding using the rapiers in rocket mode as much as possible because they're very hungry when you do! once your above 15/20k then the isp of the poodle probably surpasses the rapier and could be used more for the apoapsis climb, also don't use tthe rapiers to circularize unless you absolutely have to.

300 tonnes! close to my record for am ssto