Delta V and Asparagus Staging

[The Space Dino]

In my career mode save I was building a rocket for a Mun landing, and I know to get to the Mun and back you need around 10000m/s of delta v. I built a rocket with asparagus staging but only has 7000m/s of delta v shown by Kerbal Engineer. So, does asparagus staging affect its readings?

[Aegolius13]

Are you using 1.2 and fuel flow priority?  At the moment, KER does not seem to "get" the new fuel flow system and is underestimating the delta-v of craft that use it.  

You should be able to check the "real" delta-v in the VAB by adding in fuel lines like in the old days.  Then you can delete them again once you have the correct numbers.  Or you can leave them on if you want acurrate data during your mission, but this may not be worth the mass and drag penalty. 

Yet another option is to use a rocket equation caluclator, or do the math yourself with Excel.  But this might require carrying a lot of data out of the program.  

[FancyMouse]

Depending on how you implement asparagus. When using old-fashioned fuel lines, KER is usually correct - in this case when number isn't correct, most probable cause is that staging is messed up. When you use 1.2 fuel priority, however - KER hasn't implement that part of the logic yet. You need to sit calm, bring paper+pen or spreadsheet, and do a manual calculation.

btw, you don't need 10km/s for Mun round trip - it should be around 6km/s-ish. 7km/s is more than enough.

[DD_bwest]

while im unsure of your question regarding the mod,  your 10,000 m/s delta V number seems off.. you should be able to do it for quite a bit less. 

very conservative guesstimates:

4000 for orbit, 1000 getting there, 400 to capture,  1000 to land, 1000 back to orbit, 400 to return to kerbin.

thats only 7800,  and your initial launch could be done WAY cheaper then 4000 lol and i think capture and return are closer to 300 each.   and that gives you a ton for the landing/takeoff from the mun

 

are you planning orbital rendezvous?

[The Space Dino]

28 minutes ago, FancyMouse said:

Depending on how you implement asparagus. When using old-fashioned fuel lines, KER is usually correct - in this case when number isn't correct, most probable cause is that staging is messed up. When you use 1.2 fuel priority, however - KER hasn't implement that part of the logic yet. You need to sit calm, bring paper+pen or spreadsheet, and do a manual calculation.

btw, you don't need 10km/s for Mun round trip - it should be around 6km/s-ish. 7km/s is more than enough.

 

24 minutes ago, DD_bwest said:

while im unsure of your question regarding the mod,  your 10,000 m/s delta V number seems off.. you should be able to do it for quite a bit less. 

very conservative guesstimates:

4000 for orbit, 1000 getting there, 400 to capture,  1000 to land, 1000 back to orbit, 400 to return to kerbin.

thats only 7800,  and your initial launch could be done WAY cheaper then 4000 lol and i think capture and return are closer to 300 each.   and that gives you a ton for the landing/takeoff from the mun

 

are you planning orbital rendezvous?

You guys telling me that it only takes 7000m/s of delta v to do a Mun round trip just basically solves my problem.

I'm just using the classic fuel lines, not the 1.2 fuel flow system.

Thanks !

[DrLicor]

4 hours ago, The Space Dino said:

 

You guys telling me that it only takes 7000m/s of delta v to do a Mun round trip just basically solves my problem.

I'm just using the classic fuel lines, not the 1.2 fuel flow system.

Thanks !

Indeed, it shouldn't use more than 7000m/s of doing it right. You can do it appolo style to reduce even more delta v-costs, at least, smarter staging. Just make a lander capeable of 1200 delta-v. a command module with ± 1650, tricky part is to calculate it right, because when intersepting and making a burn to orbit mun, the command module had to drag the lander with it. So you need at least 310 delta/v with lander, and the remaining deltav without the lander because it´s left in space and a waste of fuel to take back to kerbin. First and second stage are simple to make, just as any other rocket make sure you can intersept the mun with those 2 stages, so around the 4260 delta/v. 

Info is from a delta-v map from version 1.1.3 (haven't seen one for 1.2 yet)

Spoiler

 

Edited October 25, 2016 by DrLicor

[The Space Dino]

@DrLicorthanks for the good tips there! This is my first manned ( or kerballed ) Mun landing and I actually did not expect Apollo to save delta v... Interesting. I'm just going for a simple mission with a LV-909 stage doing most of the Mun stuff. 

Still, thanks for the good tips!

[DrLicor]

@The Space Dino, at least your off a better start than me, First time I tried a mun mission I overpowered my lander a tiny but to much that I could make a minmus landing too  

Edited October 25, 2016 by DrLicor

[The Space Dino]

Just tried the Mun landing... managed to land on the Mun nicely but it still did not have enough delta v to return to Kerbin. Good thing I enabled reverting flights

When I was leaving the surface, I could not quickload, so I'll just ask why can't I quickload?

@DrLicor overpowering your rocket is actually good, in my opinion. It is obviously better to have some extra fuel left than to strand a kerbal on the Mun 

 

Edited October 25, 2016 by The Space Dino

[DrLicor]

Before quickloading you need to quicksave by pressing F5. after that you can quikload to your latest quicksave with holding F9. 

Try to make a 2 staged lander, with a very low-mass second stage. So you can put a lot of energy/delta-v out of the second stage. Try to burn slowy on you landing so you don't waste any delta-v.

 

[GoSlash27]

I would budget 6,150 m/sec DV for a Mun shot.

1,700 for boost
1,700 for LKO injection
900 for TMI burn
350 for circularization
1,150 for descent/ landing
600 for ascent/ rendezvous
350 for TKI burn

 Keep in mind that while there are many ways to shave mass and cost on a mission, there is no way to "save DV" on a mun shot.

If it were me, I would calculate DV myself using a spreadsheet.

Best,
-Slashy

 

[The Space Dino]

3 hours ago, DrLicor said:

Before quickloading you need to quicksave by pressing F5. after that you can quikload to your latest quicksave with holding F9. 

Try to make a 2 staged lander, with a very low-mass second stage. So you can put a lot of energy/delta-v out of the second stage. Try to burn slowy on you landing so you don't waste any delta-v.

 

I did quicksave but it said "could not quickload in this situation".

I've upgraded my Mun lander to have 7000m/s of delta v ( because I'm a terrible flyer ), going to do a second attempt and if it fails, I'll have to redesign it. Good thing I have a few doable contracts lying around for cash.

@GoSlash27 thanks for the helpful tips!

[Plusck]

2 hours ago, The Space Dino said:

I've upgraded my Mun lander to have 7000m/s of delta v ( because I'm a terrible flyer )

Well, that is "playing it safe".

It also allows you to hover above the surface of the Mun for about 45 minutes while deciding whether or not you want to land

Edited October 25, 2016 by Plusck

[DrLicor]

3 hours ago, The Space Dino said:

I did quicksave but it said "could not quickload in this situation".

I've upgraded my Mun lander to have 7000m/s of delta v ( because I'm a terrible flyer ), going to do a second attempt and if it fails, I'll have to redesign it. Good thing I have a few doable contracts lying around for cash.

@GoSlash27 thanks for the helpful tips!

your lander only or the whole craft?

[The Space Dino]

6 hours ago, DrLicor said:

your lander only or the whole craft?

My lander only when I was leaving the Mun's surface.

[DrLicor]

5 hours ago, The Space Dino said:

My lander only when I was leaving the Mun's surface.

With that amount of delta-v you can go to duna from there   A single trip from LKO to Duna's surface costs around 3140 delta-v, so you could make it back if you like  

[DrLicor]

Look: if you want to leave the mun and go back to kerbin, the first thing you want, is to orbit mun in the right direction. So fly east (explain it later), you don't need a high altitude, because mun has no atmosphere, only mountains... a orbit around 20km is good enough. Once you get in that orbit, you want to make your escape burn, do this at the kerbin side of mun (1).

You must think of it as a slingshot: image the mun was on a rope, and kerbin rotated the mun by spinning itself, just like you pick something with a rope and are going to spin. And because you spin, the mun gets a velocity, 542.5 m/s. But you don't want that velocity, you want to go slower. So if you make sure that your escape burn is in the opposite direction of how mun rotates around kerbin, you will reduce that slingshot effect, resulting in a lower orbit.

So try to get your escape trajectory a bit close as I'm showing with my amazing Paint™ skills  What you now basicly want, is to get back to kerbin. The fastest way would be lowering you Pe down to 30km on kerbin. But yeah, with your Ap around the 11000km, doesn't seem like a save plan. So when your at your Pe, try to lower your Ap (2) a bit, just get between the 500km and 750km.

When arriving at your Ap, lower your Pe to 30km above kerbin. You don't need to go any lower, because the atmosphere will aerobrake you. And it doesn't mind if you make another orbit, once the atmosphere brakes you, you will eventually get down on kerbin. This is the safest way of returning.

Here's something for when you're short on fuel: try to get your Pe first aroud the 45-50km before lowering your Ap. Your craft will aerobrake itself in kerbin's atmosphere and you don't have to use fuel for lowering your Ap. Note: it can take serveral orbit until your Ap is low enough to re-entry, and make sure you have good heat protection. 

Straight going to the math: make sure that the module where you want to reenter with, is as light as possible, Why? According to Newtons First Law, Force = Mass x Velocity. You can see, when you lower the mass, the force will lower to. When your craft is going trough the atmosphere, the atmosphere pushes you to go slower, so you can imagen, the lower your 'Force' is, the more effect your atmospheric aerobraking will have. So just leave a the stuff you strapped on your ship in space, get it in your return capsule, decouple and go.

9/10 of my space crafts reentring are just 3 parts: parachute(s), return capsule, heatshield. You don't need to bring your experiments with you, I mean the parts. Just let someone go on EVA, when in EVA, let him/her pick up the experiments by rightclicking on the part. Get back in your capsule and all your experiments will go with you, and not the parts.

Well, that was your space science lesson for today, any questions?   

 

Edited October 26, 2016 by DrLicor

[The Space Dino]

@DrLicorthat was the longest guide anyone gave me!  Thanks, now I know how to properly return from the Mun now.

The question is: Do you have to be right beside the Goo canister ( because I'm bringing that to the Mun ) to collect its data? Or is it just that my Kerbals are underleveled? The last time I tried it only collected the science for the thermometer.

Btw how did you even do that with Paint? That's amazing !

Thanks!

Edited October 26, 2016 by The Space Dino

[DrLicor]

5 minutes ago, The Space Dino said:

The question is: Do you have to be right beside the Goo canister ( because I'm bringing that to the Mun ) to collect its data? Or is it just that my Kerbals are underleveled? The last time I tried it only collected the science for the thermometer.

You're welcome, you have to be close to the part, almost stand on it. When right clicking it, pin the window down and get close, you'll see that something like 'take experiment' appears. Most of the time I leave all my experiment parts on the mun to save weight haha

note: every level kerbonaut can take experiments, only scientists can reset mistery goo's 

Edited October 26, 2016 by DrLicor

[The Space Dino]

Just now, DrLicor said:

You're welcome, you have to be close to the part, almost stand on it. When right clicking it, pin the window down and get close, you'll see that something like 'take experiment' appears. Most of the time I leave all my experiment part on the mun to save weight haha

Ok, so I guess I will have to jump on it lol

This is becoming a matter of more science or more survivability...

1.2's science capsule thingie really changes everything

[DrLicor]

2 minutes ago, The Space Dino said:

Ok, so I guess I will have to jump on it lol

This is becoming a matter of more science or more survivability...

1.2's science capsule thingie really changes everything

Oh indeed, I almost forgot that thing, I don't play 1.2 yet because RSS and RO aren't updated yet, but indeed, the science capsule have a big role in this

[Gilph]

@The Space DinoHi,

For Mun, if you are not interested in reusing the vessel, I've had success in using a center fuel tank, and installing four smaller fuel tanks around the bottom of it with decouplers.  Then, attach the landing legs to the outer fuel tanks.  When I land on Mun, my outer tanks are emptied on the way down. When I lift off, I decouple the empty tanks (including the landing legs) to remove the weight, increasing the delta v of the return ship. Using a terrier engine, I can do a lot on Mun early in the tech tree with that design. It's not really asparagus staging at that point, but dropping the empty tanks and landing gear right after liftoff sheds that weight at just the right time.

Hope that helps

Edited October 27, 2016 by Gilph

[DD_bwest]

once you figure out the spark is good enough for mun landings it becomes alot simpler lol  and stacking  round 8's you can store more fuel in a smaller area (same weight) with the draw back of no surface attaching on them lol

you can also mount them on the smallest rectangular strut.  those struts are great for getting around surface mount limitations 

[The Space Dino]

@Gilph thanks for those tips! I actually considered that design but I settled for my current one, which is the smallest 1.25m tank with the 3rd largest 1.25 tank with a LV-909 with landing legs attached beside it. I have yet to try that design. In terms of delta v it's kinda overkill for the Mun. Hope I don't screw it up 

@DD_bwest desperate times times comes for cheap measures lol

Edited October 28, 2016 by The Space Dino

[The Space Dino]

Bad news: the 7000 m/s delta v design still didn't work, should I redesign it or go for other stuff in career mode?

@DrLicor any ideas ?

Edited October 29, 2016 by The Space Dino