
Chandrayaan-2 Update: Lunar Orbit Insertion - signa11
https://www.isro.gov.in/update/20-aug-2019/chandrayaan-2-update-lunar-orbit-insertion
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swatkat
Here's a nice orbit simulation for Chandrayaan-2 mission:
[https://sankara.net/chandrayaan2.html](https://sankara.net/chandrayaan2.html)

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bdamm
It's a really nice tool, I had several ah-hah moments!

Does anyone know what the teleportation glitch is right at Lunar capture?

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colechristensen
n-body problems are hard, 2-body problems are easy (can by analytically
solved)

One pretty accurate way of approximating orbits is the patched conic method
where you break your n-body problem into multiple 2-body problems picking the
most influential body for specific parts of a journey.

Interplanetary journeys will have three parts ex. earth-craft, sun-craft, and
mars-craft.

The glitch might be some noise switching between two different patches.

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outworlder
> One pretty accurate way of approximating orbits is the patched conic method
> where you break your n-body problem into multiple 2-body problems picking
> the most influential body for specific parts of a journey.

So, KSP's "Sphere of Influence" ?

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colechristensen
Yup, that's the term used in engineering as well.

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aravindgp
I love the fact the chandrayaan uses earths gravity for most of its journey.
This is simply amazing idea of saving energy and realying alot on maths.
That's incredible achivement over thousands of kms.

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spectramax
Not to be a thorn in your excitement but gravity assist is a standard
technique for more than 40 years in space exploration. Literally every
spacecraft uses it in some way or the other.

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lmilcin
Not to be a thorn in your excitement but as an expert in orbital mechanics (I
have a certificate from University of Kerbin) there is absolutely no assist
anywhere in this manouver. The pattern is just raising apogee of the orbit
around Earth by performing prograde burn close to perigee.

The only reason this could have any mechanical advantage is due to Oberth
effect if the engine was low thrust type. With low thrust it takes long time
to perform the burn and so part of the burn would be performed away from
perigee which makes it less efficient. Splitting it would allow them to
overall perform it closer to perigee.

Other than that it has no advantage over straight burn (ie. directly from LEO
to Moon using Hohmann transfer), mechanically, but it could have other
advantages. Making last burn shorter makes it likely more precise than single
long burn. It also probably allowed them to perform some burns to test the
craft before the most important one. There might be other reasons like testing
communications equipment which might be difficult in LEO but they might not
want to perform it before committing to insertion.

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cryptozeus
I will get downvoted for this but man that website is pre 1980s

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sbmthakur
Many Indian government websites are old and some of them don't even have a
proper HTTPS certificate.

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saagarjha
> The orbit achieved is 114 km x 18072 km.

Are there plans to circularize this orbit, or will the lander be the only part
that enters an orbit that isn’t highly elliptical?

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ubertakter
From the _linked article_ :

"Following this, a series of orbit maneuvers will be performed on
Chandrayaan-2 spacecraft to enable it to enter its final orbit passing over
the lunar poles at a distance of about 100 km from the Moon’s surface.

Subsequently, the lander will separate from the Orbiter and enters into a 100
km X 30 km orbit around the Moon. Then, it will perform a series of complex
braking maneuvers to soft land in the South polar region of the Moon on
September 7, 2019."

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saagarjha
This doesn't answer my question of whether the orbiter will remain in its
highly elliptical orbit or not.

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olliej
“On entering Moon's sphere of influence, on-board thrusters will slow down the
spacecraft for Lunar Capture. Subsequently the orbit of Chandrayaan-2 around
the moon will be circularised to a 100x100 km orbit through a series of
orbital maneuvers.”

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ramk
The series of 4 planned orbital maneuvers are outlined here
[https://www.isro.gov.in/update/14-aug-2019/chandrayaan-2-suc...](https://www.isro.gov.in/update/14-aug-2019/chandrayaan-2-successfully-
enters-lunar-transfer-trajectory)

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sdenton4
Go go go go go!!!!!

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whydoyoucare
To the moon and back! :-)

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Koshkin
Any country that can build (or buy) rockets can do this now. So, why even
bother?

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mayankkaizen
So which country do you think can do it and still isn't doing it?

How many countries do you think are capable of doing it?

