Bop and Pol and return questions?

[Guest]

Thank you the mission is over

Edited July 4, 2019 by Guest

[Guest]

So I finished the launcher will 11000 m/s will it be enough

[Aegolius13]

1 hour ago, The Doodling Astronaut said:

Using a tylo assist, I will attempt to get a high elliptical orbit. But I heard in a video that an encounter with bop and pol at periphrasis is a bad Idea!

You may have trouble getting the apo on your elliptical orbit to hit Pol/Bop, but it should be relatively cheap for you to circularize at apoapsis and then figure out a rendezvous.  If you're in a high circular orbit it should be cheap to plane match as well. 

 

1 hour ago, The Doodling Astronaut said:

The Orbiter isn't final design since I might need a more powerful antenna. 

That is the most powerful antenna (it's even with the big relay dish, but the relay function doesn't affect range and shouldn't be necessary here.  This very useful table confirms that if you have a maxed out ground station, one of those is good anywhere in the system (assuming no line of sight blockage). 

https://wiki.kerbalspaceprogram.com/wiki/CommNet

1 hour ago, The Doodling Astronaut said:

My first missions to Jool costed around 10000 m/s in total meaning they were really inefficient. So even if you can tell me the total from the Dv map would be nice since I still don't get em.

Delta-v maps are arguably less useful at Jool than anywhere else since there's so much variation based on gravity assists.  If you nail them the insertion will cost you almost nothing, but sometimes a mediocre assist doesn't actually help.

 

My rule of thumb is that a transfer to Jool takes around 2,000 m/s, and a return from Laythe is about 1,000.  And it's good to reserve a few hundred m/s for course corrections.  Not sure how the outer moons compare with Laythe on return delta-v - they're higher in the gravity well (which is good), but you get less Oberth effect (which is bad).  As mentioned, insertion is a wildcard due to gravity assists, but it should take the same amount to enter as to leave, so for Laythe at least it might be around 1,000 m/s.

1 hour ago, The Doodling Astronaut said:

4 Ablative heat sheilds?

I would like to know the limit to an ablative heat shield. 

It's really, really high.  I've gone up to 7km/s reentry speed and been fine.  Jool should be well under that.  Just make sure you have total coverage.

 

1 hour ago, The Doodling Astronaut said:

Bop has a weird inclination and is why I assumed to leave the return craft in low pol orbit but is it better to leave it in Bop orbit. Also can I land in a way that if I leave bop I am in equatorial orbit?

If you have the lander delta-v, leaving in Pol orbit makes sense.  The better inclination will remove one variable from plotting your return, which is always nice.

How you land on Bop is not very important for how you leave.  You should be able to leave in an equatorial orbit, but you will need to (1) add a LOT of normal/antinormal in your exit burn, and (2) time it so that you leave when Bop intersects the equatorial plane (i.e., its ascending or descending node). 

 

 

 

[Aegolius13]

Forgot one point:

4 hours ago, The Doodling Astronaut said:

I don't know how returning to kerbin should work. Should I get gravity assists and how to do it in order?

IMO, gravity assists are a lot harder when leaving than when entering.  It's pretty hard to get your exit trajectory where you want it.  So I don't usually bother.

One alternative trick to consider, if you're leaving from Pol: I think this is often called an Oberth Maneuver.  The idea is to drop your periapsis down to very near Jool (i.e, so you have a very elliptical orbit with Jool at peri and Pol at apo).  Then, when at the Jool peri, perform your exit burn.  You get tons of help from the Oberth effect and your apo is already near escape velocity to begin with.

The trick is to time it so that elliptical orbit "points" in the right direction -- i.e, so that after the escape burn, you're heading the opposite direction from Jool's orbit around the sun.  

EDIT - Ehh, I did a little testing on this, and the Oberth dive doesn't make much of a difference in delta-v budget for Pol>Kerbin.  And it's quite fussy to time right.  So I'd probably suggest using the direct method.

Edited June 30, 2019 by Aegolius13

[Foxster]

Coupla thoughts on your craft because reducing mass will make it easier to hit the dV you need...

Lander: That's a heavy pod for the crew; there are lighter. The adapters make it look nice but only add mass. Those landing gear are heavy; the gravity is low and you can likely do without them. Consider some staging to drop used tanks. Do you really need two crew?

Mothership: What are all the heavy batteries for? That's a heavy probe core you chose. Looks like a lot of chutes; that 2-man capsule will re-enter and land OK with just one small chute. An unusual choice of engines; how's the isp on those? You can return directly from Jool without making Kerbin orbit if you re-enter just the capsule and a heatshield with 20% ablator.  

Edited June 30, 2019 by Foxster

[Guest]

9 hours ago, Foxster said:

Coupla thoughts on your craft because reducing mass will make it easier to hit the dV you need...

Lander: That's a heavy pod for the crew; there are lighter. The adapters make it look nice but only add mass. Those landing gear are heavy; the gravity is low and you can likely do without them. Consider some staging to drop used tanks. Do you really need two crew?

Mothership: What are all the heavy batteries for? That's a heavy probe core you chose. Looks like a lot of chutes; that 2-man capsule will re-enter and land OK with just one small chute. An unusual choice of engines; how's the isp on those? You can return directly from Jool without making Kerbin orbit if you re-enter just the capsule and a heatshield with 20% ablator.  

So the lander design is big for one reason: I have a lot of material on it. I don't have a video but It has a lot of gear that will be disposed after landing (deployable experiments and arms.) The lander is full with experiments and it's just cause I want it to be more realistic with space for crew! The Landing legs elevate the surface gear. The batteries I've tested and are used for powering heavy transmission. Now for the parachutes, The main reason is because I want it to be G-force friendly. so I want the crew to have low G-forces. The engines were chosen after testing many MANY missions with three options with small engines, nuclear, and the ones on the mothership. I decided the side mounted because I can change how efficient. Plus it gives me a larger variety of engine control (so I can chose between two-twelve engines!)

[Guest]

I have Arrived with 5000 Meters left! -500 with the encounter and  -1000 with circularizing unless if I find a cheaper way!

[Guest]

Had to revert flight due to the lander gimbal failure. So I am going to redesign the lander and maybe put some tips from you guys or might just use a previous lander design 

[Guest]

Update wasn't gimbal failure but electric charge...  I'm now triggered 

[Guest]

Update I have landed both on Pol and Bop currently on Bop surface and will be returning to cruise stage that will return me to the orbiter

[18Watt]

1.  Is it enough?  Depends on wether you're doing gravity assists or not.  I don't.  I could make 2800 work, but it would not leave much margin.  But, it's possible, even without gravity assists.

2. Total Fuel Cost?  No idea.  Again, I think you could get back to Kerbin from Bop or Pol with 2800.  

3. Best tips?  I rely on gravity assists when entering Jool's system.  Pretty easy to get a Tylo encounter.  You could get similar savings when leaving Jool, but making gravity work in your benefit is much harder when leaving.  It's possible to spend hours planning a gravity-assist departure, and end up realizing you actually ended up worse off because of your efforts.  I tend to count on gravity assists when entering Jool, but don't bother with gravity when leaving.

4. Heat shield?  If your heat shield covers the entire craft, you should be fine aero-braking back at Kerbin.  Heat shields work really well in KSP.  But, just in case, do a quick-save before hitting Kerbin's atmosphere.

5. Inclination?  Yes, since I depart Jool with 'brute force' instead of gravity-assists, I do try to keep my inclination on exit as low as possible.  However, if you are just barely leaving Jool, and then doing a Hohman transfer, Bop's inclination is probably not going to be significant.  If on the other hand you are dropping your PE to take advantage of Jool's gravity on exit, any inclination will be amplified on exit.  I normally try to depart from Pol or Laythe.  Departing from Bop, I would either fix my inclination first, or maybe just barely exit Jool's SOI and fix inclination then.  Or, at that point, maybe gambling with a gravity-assist from say Tylo to fix inclination.

[Guest]

I have successfully finished the mission! thank you all for helping