Author Topic: Israeli robotic lunar lander  (Read 2123 times)

Offline JayUtah

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Re: Israeli robotic lunar lander
« Reply #15 on: February 24, 2019, 04:52:27 PM »
Isn't that known as the Oberth Manoeuvre?  You get more bang for your buck at high velocity than low.

Yep.
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Offline ka9q

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Re: Israeli robotic lunar lander
« Reply #16 on: February 25, 2019, 06:20:34 PM »
Incidentally, how is it that multiple short burns to raise the apogee are more efficient than a single longer one? Is it that the efficiency of the burn is greatest when the spacecraft is closest to perigee, and this efficiency drops off considerably even minutes either side of perigee?
This assumes an instantaneous burn. If the required burn time is too long, it might be more efficient to split it up to a bunch of shorter ones.

Offline ka9q

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Re: Israeli robotic lunar lander
« Reply #17 on: February 25, 2019, 06:24:57 PM »
I haven't studied the Beresheet trajectory, but another consideration is that it is more efficient to do plane changes at apogee. If one is necessary along with apogee raising, it might be more efficient to establish an intermediate apogee to do the plane change.

Offline bknight

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Re: Israeli robotic lunar lander
« Reply #18 on: February 26, 2019, 12:26:49 PM »
First burn was successful raising the perigee to 600 Km.

https://spacenews.com/spaceil-lunar-lander-makes-first-post-launch-maneuvers/
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Offline bknight

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Re: Israeli robotic lunar lander
« Reply #19 on: March 01, 2019, 01:12:34 PM »
A second burn successfully completed after a aborted attempt on Monday.  The new Apogee is 131000 Km.

https://www.space.com/israel-moon-lander-beresheet-engine-firing.html
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Offline bknight

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Re: Israeli robotic lunar lander
« Reply #20 on: March 21, 2019, 07:42:14 AM »
A final burn has been completed for the craft to enter an orbit of the Moon.

https://www.israelnationalnews.com/News/News.aspx/260690
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Offline raven

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Re: Israeli robotic lunar lander
« Reply #21 on: March 21, 2019, 11:23:29 PM »
A final burn has been completed for the craft to enter an orbit of the Moon.

https://www.israelnationalnews.com/News/News.aspx/260690
"Israel’s first spacecraft performed a special maneuver Wednesday night, aimed at putting the lunar lander into position to achieve a stable lunar orbit."
"Israel’s first spacecraft."
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Offline ka9q

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Re: Israeli robotic lunar lander
« Reply #22 on: March 24, 2019, 01:33:48 PM »
The article says it was a plane change. That's as I had expected, since a plane change is more efficient at a high apogee where the orbital velocity is lowest. They can be extremely expensive in low orbit.


Offline bknight

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Re: Israeli robotic lunar lander
« Reply #23 on: March 28, 2019, 08:35:14 AM »
Beresheet Gears up for Lunar Rendezvous
Quote
As of Thursday, 28 March, Beresheet is making its final orbit around the Earth. On 30 March, it will hit perigee, buzz past its home planet one last time, and head towards the Moon, roughly 405,000 kilometers distant. SpaceIL senior engineer Yoav Landsman said the spacecraft will make a small trajectory correction on 1 April. The duration of the lunar insertion burn on 4 April, as well as the parameters of the initial lunar orbit, have yet to be decided, but SpaceIL was originally planning for an orbit roughly 10,000 by 300 kilometers. Landing won't happen for another week, on 11 April.

http://www.planetary.org/blogs/jason-davis/beresheet-gears-up-for-lunar.html
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Offline Dalhousie

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Re: Israeli robotic lunar lander
« Reply #24 on: March 29, 2019, 05:10:54 PM »
At least one web user I know at ATS is frothing at the mouth that there is Israeli government money involved so it can't be private, and, well, you know, Jews.

Since it is built by a company that is heavily underwritten by the Israeli government the hype about it being the first private missions is a bit excessive.

Offline bknight

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Re: Israeli robotic lunar lander
« Reply #25 on: April 04, 2019, 11:19:02 AM »
From yesterday
Israel’s Beresheet lander arrives in lunar orbit

https://spaceflightnow.com/2019/04/03/israels-beresheet-lander-heads-for-make-or-break-maneuver-to-enter-lunar-orbit/

Landing attempt n the 11th still.

ETA:  LO, I realize that this is in the hoax forum, if you want to move it to an appropriate thread.
Truth needs no defense.  Nobody can take those footsteps I made on the surface of the moon away from me.
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Offline JayUtah

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Re: Israeli robotic lunar lander
« Reply #26 on: April 04, 2019, 11:33:13 AM »
ETA:  LO, I realize that this is in the hoax forum, if you want to move it to an appropriate thread.

I was going to ask about that.
"Facts are stubborn things." --John Adams

Offline bknight

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Re: Israeli robotic lunar lander
« Reply #27 on: April 04, 2019, 12:17:11 PM »
ETA:  LO, I realize that this is in the hoax forum, if you want to move it to an appropriate thread.

I was going to ask about that.

I freely and openly confess an error on my part in the OP.  :-[
Truth needs no defense.  Nobody can take those footsteps I made on the surface of the moon away from me.
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Offline LunarOrbit

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Re: Israeli robotic lunar lander
« Reply #28 on: April 05, 2019, 09:00:43 AM »
LO, I realize that this is in the hoax forum, if you want to move it to an appropriate thread.

No problem.
It suddenly struck me that that tiny pea, pretty and blue, was the Earth.
I put up my thumb and shut one eye, and my thumb blotted out the planet Earth.
I didn't feel like a giant. I felt very, very small.
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Offline bknight

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Truth needs no defense.  Nobody can take those footsteps I made on the surface of the moon away from me.
Eugene Cernan