[AAR] The Grand Tour - Voyage To The Planets

[[ Jeremy ]]

Insertion Burn:

While aerobraking is an efficient option, there are many risks that come with it, the crew haven't been inane sort of real gravity for over a year at least, a couple of years at most and coupled with the tat that Proteus is in no good condition, aerobraking is almost suicidal. And as Ned said, even if something occurs, Kerbin is waiting for them.

[MedwedianPresident]

I think aerobraking should be used to spare fuel and reduce the G-forces. I'll go for a 15 kilometer periapsis.

[czokletmuss]

(and does the poll closing time have anything to do with the next chapter realise?)

Yup. It means that after the poll is closed and we have a result, I'll play the game and write AAR afterwards. So the next chapter will be released in best case scenario on Tuesday.

EDIT: So far we have a draw (2:2) - please use the format described earlier, it'll make it easier for me to check the votes quickly before I start playing/writing. Thank you

BTW I wonder if there is going to be someone Genre Savvy about this poll...

Edited February 8, 2014 by czokletmuss

[QuesoExplosivo]

Reason 1: The engines may blow up. I think this is a greater risk than damage from aerobraking.

Reason 2: Saving on fuel means more margin for error later.

(I have read this AAR from the beginning, and joined the forum to vote in this poll.)

[silentdragon]

Insertion Burn

I was going to vote for Aerobraking initially, but then I realised how fatal this would be with a ship (and crew!) in this condition and without BERTYs calculations. Sure, after all we know the fusion cores could just blow up, killing everyone, but I just don't think this is going to happen, and in case the engines fail, they still have the free return to Kerbin.

[popeter45]

i had i strange idea

detach the lander before entering the soi

land it and collect the duna crew then reservoir with porteus

all while never changing proteus flight path

free return

would be hard but very cool

Edited February 8, 2014 by popeter45

[iDan122]

Insertion burn:

No significant physical stress.

No stress on the ship

Less risky, easier to complete.

If failed, Proteus will be on is way to Kerbin safely.

Fuel can be spent without hesitation, I mean the EMU arrives 2 months after Proteus.

[ElJugador]

i had i strange idea

detach the lander before entering the soi

land it and collect the duna crew then reservoir with porteus

all while never changing proteus flight path

free return

would be hard but very cool

http://i.imgur.com/JAiCRTN.png

The LAMGML doesn't have enough fuel for that kind of maneuver I think.

[Raptor831]

Insertion Burn

Every time they aerobrake bad things happen. Something gets damaged (and they have few spare parts left) or someone dies (Jool). Best to at least face the demon you can actually fight. If the cores decide to fail, at least there is a shutdown that can happen or something the crew can do. With an aerobrake, once you hit air you're at the mercy of the physics, and nothing can really help. Maybe a correction burn, but then we're back to burning anyway.

Although, a combination of a light aerobrake in the upper atmosphere (if that's even worth doing on Duna...) and a burn might help. Lower Gs, less heat, less time using the fusion cores...

[czokletmuss]

i had i strange idea

-snip-

It's not strange, it's crazy.

But... maybe it's Crazy Enough To Work? I dunno, maybe you should run some numbers - that could convince Jeb

EDIT: Also remember that LAMGML can operate independently for no longer than 5-7 days (life support). So from the moment it undocks "Proteus" to the moment it docks after Duna landing the whole (hypothetical) operation has to take less than a week.

Edited February 8, 2014 by czokletmuss

[popeter45]

good point

hope it can work

i calculated it takes ~ 3300m/s +/- 1000 m/s in vacuum to do the job (using stats from the ksp wiki)

maby a simulation can see if it works? (cant run mods on laptop well)

edit: the length of the mission mostly depends on how long proteus stays in the duna soi

and how many kerbals in a emergency can LAMGML carry?

could LAMGML resupply on duna as well?

Edited February 8, 2014 by popeter45

[Itsdavyjones]

I vote for a combo approach. Utilizing a partial aerobreaking and then burning to get into orbit. It would lower the amount of stress on both the hull and the engines by this approach.

[Michaelo90]

good point

hope it can work

i calculated it takes ~ 3300m/s +/- 1000 m/s in vacuum to do the job

maby a simulation can see if it works? (cant run mods on laptop well)

If i understand the dv charts correctly, that's just what you need to land and get back to low orbit. Then you have to get a kerbin return trajectory and then catch up to proteus. That's a lot more.

Also, great chapter as always

[popeter45]

we now have 3 (4 if you count my crazy idea)

aerobrake

powered orbital insertion

hybrid powered aerobrake

[czokletmuss]

If i understand the dv charts correctly, that's just what you need to land and get back to low orbit. Then you have to get a kerbin return trajectory and then catch up to proteus. That's a lot more.

Also, great chapter as always

Thanks

Yup - relative speed of "Proteus" to Duna is going to be quite substantial. That's how it looked like during the first Duna encounter (Chapter 21):

we now have 3 (4 if you count my crazy idea)

aerobrake

powered orbital insertion

hybrid powered aerobrake

Yeah, I guess I'll update my post about the poll

EDIT:

POLL - AEROBRAKING OR ORBIT INSERTION BURN? OR SHOULD JEB TAKE THE THIRD OPTION?

Jeb have to choose. Whatever the choice is going to be, it would have immense impact on what's about to happen once “Proteus†arrives in Duna SOI. But this time you can help him.

Please vote by posting and please use this format in your comments:

Aerobraking

(thougthful arguments why this is a better option)

or

Insertion burn

(thougthful arguments why this is a better option)

or

Other option (combo approach, direct landing and rendez-vous et cetera)

(describe what it is)

(thougthful arguments why this is a better option)

The poll will be closed at midnight on Monday (24:00/12:00PM, Central European Time [GMT+1]).

This is a test of some interactivity I'm planning to introduce in my upcoming secret project. Oh and your arguments will be used in the story by characters!

Have fun!

Oh and remember that Duna base is NOT on the equator - it's quite near to the south pole actually.

Edited February 8, 2014 by czokletmuss

[popeter45]

Thanks

Oh and remember that Duna base is NOT on the equator - it's quite near to the south pole actually.

well that destroys my idea

i was thinking to a launch direct to interplanetary

[ekim98]

Insertion Burn

This is a safer, wider area of attack and if the fusion cores do malfunction, then they can just continue on the free return trajectory anyway. It's not like the crew on Duna have any chance of survival anyway.they are most likely dead or soon will be. and if they aren't, then jeb doesn't have to worry about them. KSC can just send a shuttle for them later.

Edited February 8, 2014 by ekim98

[Lundmunchkins]

*AEROBRAKE*

*The crew will have more fuel to reach Kerbin

*The fusion cores won't go kaput

*It's cooler

[PwnedDuck]

Early insertion burn with the option to Aerobrake (positioning for that by RCS) if the fusion cores fail.

[BigOto2]

This is a difficult question to answer. I currently lean toward engine-only braking, because if the engines appear too unstable before the burn, or fail to ignite, then they can take the free-return option. However, if the engines fail midway through, they could be stranded in some wonky eccentric Duna orbit, or worse, back out into solar orbit without the Kerbin encounter or any hope of returning home (would RCS be enough to correct for it in this case?). A light aerobraking plus engines might make it safer by reducing burn time, but again if the engines are going to fail, we don't have enough information on WHEN they might do so and if aerobraking would prevent it from happening with reduced burn time, and this rules out the free return trajectory option. A full aerobraking seems too risky at this point, but again, I don't really have enough objective information to know if it's any safer than engines on for a few minutes (which didn't prove to be any safer during the Eve flyby).

Leaving open the Kerbin free return trajectory seems like the most sensible choice here. They will make an attempt to save the Duna crew, and if they need to use the free return they will already know that saving them will be impossible. Therefore: Insertion Burn

[Spuds]

OTHER OPTION: Combo Braking with possible Ike assist

As other people have stated, you could use a combination Aerocapture and Retroburn to slow you down; the fusion cores wouldn't be stressed as much and the hull would be a bit safer during aerobraking.

Alternatively, if you have an Ike encounter, you could use a gravity assist to slow you down by crossing over the prograde side of Duna. Although, you'll have to be in a pretty tight margin to do so, so that may not be possible.

I suggest sending one of those Kethane mining probes (the one BERTY tried to kill Jeb with) to examine the base. you want to know what happened down there before you go there. Since it's in the southern hemisphere, I wonder... Wait, nope, possible spoilers.

Edited February 8, 2014 by Spuds

[czokletmuss]

OTHER OPTION

As other people have stated, you could use a combination Aerocapture and Retroburn to slow you down; the fusion cores wouldn't be stressed as much and the hull would be a bit safer during aerobraking.

Alternatively, if you have an Ike encounter, you could use a gravity assist to slow you down by crossing over the prograde side of Duna. Although, you'll have to be in a pretty tight margin to do so, so that may not be possible.

I suggest sending one of those Kethane mining probes (the one BERTY tried to kill Jeb with) to examine the base. you want to know what happened down there before you go there. Since it's in the southern hemisphere, I wonder...

Reverse gravity assist with Ike is an interesting idea - it has all the benefits of aerobraking with no disadvantages. It does however require precision, some correction on the way probably and of course luck (Ike has to be in the right place during approach).

There are no probes. Besides LAMGML docked to "Proteus" there is only Automatic Miner Unit attached to Payload C which will arrive in Duna SOI 2 months after the crew. Take a closer look at "Proteus" on some screenshots if you don't believe me - there's no more payload besides kethane tanks

Edited February 8, 2014 by czokletmuss

[skykooler]

I also like the idea of an Ike assist. Because Ike has such a large SOI, depending on where you point nearly 3/4 of Ike's orbit is in a valid place for gravity assist. And because there's no variables like in aerobraking, the crew have plenty of time to fine-tune the trajectory, which might be necessary without BERTY's help.

[czokletmuss]

To make it even better, "Proteus" is coming almost precisely from the ecliptic plane, which means that initial inclination shouldn't be larger than 10 degrees, thus making reverse gravity assist even easier

[silentdragon]

Well if an Ike gravity assist would be possible, I would of course do that, because, as you said, it has all the advantages of aerobraking but no disadvantages.