Oribiting Minimus; not just a flyby or crashing into it.

[Skorpychan]

HOW.

I managed to get a minimus encounter today, but couldn't manage to get an orbit. It was either a flyby, or a stable orbit with a periapsis somewhere in the middle of the body. What did I do wrong?

What I actually did was get a kerbin orbit with an apoapsis out past minimus, then noded my way to a similar inclination after gaining speed from a mun encounter, time-warped until I got an encounter with Minimus, then burned retrograde once in the SoI of Minimus.

Was I carrying too much speed to minimus, or not enough?

Do I need to mess around with radial burns to get a higher encounter?

Should I take the flyby and mess with the orbit after?

Edited July 18, 2013 by Skorpychan

[Boex]

*Minmus

a stable orbit with a periapsis somewhere in the middle of the body. What did I do wrong?

Well...that's definitely not a stable orbit...but...

It sounds like you're just over-doing your retro-burn around Minmus. Bear in mind that your relative speed to Minmus is likely to be quite low as you're a long way from Kerbin.

Remember that you can hit the little arrow at the bottom middle on the map screen and it will bring up your nav-ball. Find the retrograde marker and burn towards it, but stay in the map view so you can keep and eye on your periapsis.

[tavert]

Any encounter with Minmus' sphere of influence means you're almost there. Practice getting an encounter reliably by adjusting the timing of your ejection maneuver out to Minmus' orbit and plane change into its inclination. You can also try making small adjustments to lower the periapsis of your Minmus encounter - this ends up being more efficient in the end if your eventual destination is to land on the surface.

If you get into a "stable" orbit around Minmus but your periapsis is below the surface, it just means you slowed down a bit too much. Turn back around to prograde and speed up a tiny bit to raise your periapsis to a non-crashy altitude.

[stupid_chris]

You're overdoing things a lot. Just set a maneuver around Kerbin that expands out to Minmus's orbit, then just drag the node around your orbit until you get an encounter with Minmus. Do that maneuver, then before time warping, set a maneuver halfway through to Minmus, and then play with the controls until you get a nice periapsis, normally the main factor you'll want to play with is your orbital inclination (they purple markers on the node) to get the right encounter. Then, when you reach Minmus, just burn retrograde while keeping the map mode up until you get a nice orbit

[SRV Ron]

HOW.

I managed to get a minimus encounter today, but couldn't manage to get an orbit. It was either a flyby, or a stable orbit with a periapsis somewhere in the middle of the body. What did I do wrong?

What I actually did was get a kerbin orbit with an apoapsis out past minimus, then noded my way to a similar inclination after gaining speed from a mun encounter, time-warped until I got an encounter with Minimus, then burned retrograde once in the SoI of Minimus.

Was I carrying too much speed to minimus, or not enough?

Do I need to mess around with radial burns to get a higher encounter?

Should I take the flyby and mess with the orbit after?

Generally, when you get an encounter with a apoapsis, you plan the orbital maneuver at the apoapsis to circularize the orbit. If you were getting a collision course, you had the burn set up wrong or retro burned for too long. It doesn't take much Delta V to enter into Minmus orbit. A short radical burn would push your periapsis path off the moon's surface.

[Skorpychan]

Okay, that makes sense. I just sent a lander out, figuring that if I was going to crash, I may as well INTEND to.

Instead, I managed to make a decent orbit, that I then had to retro-burn into the surface. Plenty of fuel left, though; I've definitely got enough to send kerbals there. And this is on my SMALLER lifter! Time to start landing kerbals and bases there.

[Monkeh]

Only tip I have for Minmus is DO NOT, WHATEVER YOU DO, use the jet pack on EVA. I managed to build up enough speed in the very low gravity that I was tumbling and bashing into the floor for what looked like a few miles before slowing down enough to regain control. Was a helluva fun until I got carried away, managed to build up a whole load of speed off a ridge and smashed my little intrepid explorer into the surface a bit too fast. He promptly died in a puff of regolith and smoke.

Jetpacks don't kill people, low gravity kills people. REMEMBER THAT KIDS!

[Skorpychan]

Oh, I learned that on the mun. First jetpack flight ended in a puff of dust and a dead kerbal.

Can I achieve orbit with a jetpack, though?

[stupid_chris]

Oh, I learned that on the mun. First jetpack flight ended in a puff of dust and a dead kerbal.

Can I achieve orbit with a jetpack, though?

From Minmus, you can get in orbit with the Jetpacks, and even return to Kerbin.

[Skorpychan]

WHAT. Seriously? Those are some ridiculous jetpacks.

At least they can return in an emergency, though.

[dave4002000]

Minmus' gravity is only a fraction of what it is on Kerbin. ~0.5m/s² versus the ~10m/s² on Kerbin. Even without the jetpack, you can jump ridiculously high on Minmus

As for getting a stable orbit, burn for an encounter. Then halfway between Minmus and Kerbin, set up another maneuver node and burn to put your periapsis at about 20km. Time warp to that 20km periapsis, turn retro-grade and burn while watching the map. Stop burning when your apoapsis lowers to that same 20km. Like everyone has said, it doesn't take much throttle to circularize and you can easily over-do if you're not paying attention.

Edited July 18, 2013 by dave4002000

[stupid_chris]

WHAT. Seriously? Those are some ridiculous jetpacks.

At least they can return in an emergency, though.

Yep If you time yourself right, you can even return to Kerbin from Gilly using the EVA jetpacks

[Skorpychan]

Yep If you time yourself right, you can even return to Kerbin from Gilly using the EVA jetpacks

This begets a challenge; how far away can you get back to kerbin from by jetpack?

[stupid_chris]

This begets a challenge; how far away can you get back to kerbin from by jetpack?

For now, I think it's the only two places people have been able to come back to KErbin from the ground. You need the gravity on the ground to be low enough so you can orbit, then you need a relatively low transfer delta V cost. I think the jet backs are just shy of 500m/s of delta V, so from Gilly and Minmus, orbiting and coming back can be done. Orbiting and having a bunch of fuel left can also be done from Pol and Bop, but the transfer to Kerbin won't make it through :l

[Cashen]

Someone should try getting back from Pol. Second lowest gravity in the system after Gilly, and very far out in Jool's sphere of influence.

[stupid_chris]

Someone should try getting back from Pol. Second lowest gravity in the system after Gilly, and very far out in Jool's sphere of influence.

The transfer DV from outside Jool's SOI to Kerbin is 965m/s. Not really happening.

[Skorpychan]

The transfer DV from outside Jool's SOI to Kerbin is 965m/s. Not really happening.

That's a hohmann transfer, rather than slingshotting off things, though.

If I could end up in a wide solar orbit after a surprise Mun encounter at high timewarp, then who knows what a jetpacking kerbal can do.

[stupid_chris]

That's a hohmann transfer, rather than slingshotting off things, though.

If I could end up in a wide solar orbit after a surprise Mun encounter at high timewarp, then who knows what a jetpacking kerbal can do.

The closest thing to slingshot with is Dres, and it's still too far, from Jool it's about 600m/s to get there to slingshot. Getting a gravity assist from Eeloo would not be possible due to the face it's orbit is higher and you do not have much maneuverability to come in at the right angle from a jetpack from Jool.

[draeath]

Oh if you want to minimize your retro even more, try to approach minmus from Minmus' prograde-side passing around the outside (eg on the side facing away from Kerbin). When the gravity of Minmus pulls you it will pull you "back" and slow you down some. You can do the opposite if you want to leave Kerbin (though using the Mun for this is more effective).

A picture is worth a thousand words, though, so have a ponder:

[lammatt]

crash course>> burn towards a direction which gives you the horizontal speed you need

otherwise >> burn towards the retrograde vector

(think about the high school physics you learned)

Edited July 18, 2013 by lammatt

[Mr Shifty]

Yep If you time yourself right, you can even return to Kerbin from Gilly using the EVA jetpacks

One of my favorite missions I've ever seen posted was by metaphor for the smallest vessel challenge. Uses a tiny rocket to slingshot Jebediah to suborbital from Duna's surface, then finished the orbital rendezvous with a jetpack. 2.93 tons on the launchpad got Jeb to Duna's surface and back to Kerbin. 483364

[Skorpychan]

Oh if you want to minimize your retro even more, try to approach minmus from Minmus' prograde-side passing around the outside (eg on the side facing away from Kerbin). When the gravity of Minmus pulls you it will pull you "back" and slow you down some. You can do the opposite if you want to leave Kerbin (though using the Mun for this is more effective).

A picture is worth a thousand words, though, so have a ponder:

I think I did that on my kerbed attempt. Tried a bigger lifter, and ended up having to drop the transfer stage not-empty, to free up the landing legs.

crash course>> burn towards a direction which gives you the horizontal speed you need

otherwise >> burn towards the retrograde vector

(think about the high school physics you learned)

I didn't learn astronautics in school, though. I took Astrophysics, but that's the big stuff that makes your brain hurt.

[Skorpychan]

Well, THAT was an interesting fail. Know how I went for a flyby rather than a crash? Only needed about 3k delta V to get what might be a Duna encounter.

[dave4002000]

Well, THAT was an interesting fail. Know how I went for a flyby rather than a crash? Only needed about 3k delta V to get what might be a Duna encounter.

Well, that's one way of getting to Duna..lol But it's about 2000m/s more expensive than just going there directly from Kerbin