Author Topic: Beresheet, SpaceIL Israeli Moon mission  (Read 143548 times)

Offline mcgyver

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Re: Spaceil Israeli Moon mission
« Reply #40 on: 02/24/2019 12:57 pm »
But Beresheet does not make gravity assistance
He in the perigeum ignites the engine and lifts the apogeum.
It uses the oberth effect.
Sorry, didn't know about Oberth effect, I thought any maneuver involving stealing energy during a flyby was called "gravity assist". (Or maybe it's just like that, and Oberth and Slingshot are two different types of gravity assist, I don't know.


I can't find an Oberth simulator. :-(




Offline lamid

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Re: Spaceil Israeli Moon mission
« Reply #41 on: 02/24/2019 01:21 pm »
https://en.wikipedia.org/wiki/Oberth_effect

If the probe moves only in Earth SOI it is a movement in a gravitational two-body problem and has eliptic orbit.

gravity assist
https://en.wikipedia.org/wiki/Gravity_assist
« Last Edit: 02/24/2019 01:45 pm by lamid »

Online FutureSpaceTourist

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Re: Spaceil Israeli Moon mission
« Reply #42 on: 02/24/2019 03:02 pm »
https://twitter.com/jeff_foust/status/1099699670291501058

Quote
SpaceIL says its Beresheet lunar lander successfully performed its first maneuver earlier today, which “took into account” issues with its star trackers. Next maneuver is late Monday.

Edit to add:

https://twitter.com/jasonrdavis/status/1099704747156590595

Quote
Beresheet fired up its main engine and successfully completed its first apogee maneuver!
« Last Edit: 02/24/2019 03:39 pm by FutureSpaceTourist »

Offline Comga

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Re: Spaceil Israeli Moon mission
« Reply #43 on: 02/24/2019 11:57 pm »
But Beresheet does not make gravity assistance
He in the perigeum ignites the engine and lifts the apogeum.
It uses the oberth effect.
Sorry, didn't know about Oberth effect, I thought any maneuver involving stealing energy during a flyby was called "gravity assist". (Or maybe it's just like that, and Oberth and Slingshot are two different types of gravity assist, I don't know.

I can't find an Oberth simulator. :-(
Until a spacecraft gets far enough from the primary body it is orbiting, so that another body affects its trajectory, it can’t “steal” any velocity.
The Oberth effect means that burns have greater effects when the spacecraft is at higher velocity. That’s why the first burn took 30 seconds to raise the perigee from 200 to 600 km. That burn was done near apogee when the spacecraft was traveling very slowly. 
The upcoming burn at perigee to raise the apogee by 80,000 km won’t take much longer than the first burn.
What kind of wastrels would dump a perfectly good booster in the ocean after just one use?

Offline Steven Pietrobon

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Re: Spaceil Israeli Moon mission
« Reply #44 on: 02/25/2019 06:08 am »
Shouldn't this be in the Commercial Space Flight section? That's the first place I looked for this. This isn't a science mission really.

It will be performing two science experiments. Its carrying a magnetometer and a light reflector, used to measure the local magnetic field strength and the distance of the Moon to the Earth.
Akin's Laws of Spacecraft Design #1:  Engineering is done with numbers.  Analysis without numbers is only an opinion.

Offline Bogeyman

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Re: Spaceil Israeli Moon mission
« Reply #45 on: 02/25/2019 07:18 am »
Wasn't it mentioned somewhere that Beresheet will snap some photos during it's flight to the moon?

Offline flyright

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Re: Spaceil Israeli Moon mission
« Reply #46 on: 02/25/2019 06:12 pm »
Are there any details available on the issue with the star trackers?
Wondering if the trackers are just impaired, or maybe out of commission?

Latest I've seen on the issue is from Jeff Foust:
https://twitter.com/jeff_foust/status/1099702465082077184

Offline mn

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Re: Spaceil Israeli Moon mission
« Reply #47 on: 02/25/2019 08:01 pm »
Are there any details available on the issue with the star trackers?
Wondering if the trackers are just impaired, or maybe out of commission?

Latest I've seen on the issue is from Jeff Foust:
https://twitter.com/jeff_foust/status/1099702465082077184

The statement about yesterday's engine firing included this sentence:

Quote
The maneuver was planned taking into account problems identified in the star trackers after launch

Offline lamid

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Re: Spaceil Israeli Moon mission
« Reply #48 on: 02/25/2019 11:02 pm »
TLE
ep=19056.120

668.0 x 69020.7 km
27.011°

Offline ccdengr

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Re: Spaceil Israeli Moon mission
« Reply #49 on: 02/25/2019 11:12 pm »
Are there any details available on the issue with the star trackers?
Wondering if the trackers are just impaired, or maybe out of commission?
It's not uncommon for star trackers to have baffle problems which cause them to not work when pointed closer to the sun than some critical angle.  Hopefully they have another differently-oriented tracker they can switch to, or the flexibility to reorient the spacecraft, to work around this issue.

Offline mn

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Re: Spaceil Israeli Moon mission
« Reply #50 on: 02/26/2019 04:16 am »
http://www.israelnationalnews.com/News/Flash.aspx/449107

Quote
Beresheet spacecraft's maneuver cancelled

On Monday night at around midnight, another maneuver was planned for the Beresheet spacecraft as it passed near Earth, in an area without communication.

During the pre-maneuver phase the spacecraft computer reset unexpectedly, and the maneuver was automatically cancelled.

The engineering teams of SpaceIL and IAI are examining the data and analyzing the situation.
At this time, the spacecraft’s systems are working well, except for the known problem in the star tracker. The control center has contact with the spacecraft according to plan and it continues its previous orbit until the next maneuver.

Offline Comga

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Re: Spaceil Israeli Moon mission
« Reply #51 on: 02/26/2019 04:32 am »
Shouldn't this be in the Commercial Space Flight section? That's the first place I looked for this. This isn't a science mission really.

It will be performing two science experiments. Its carrying a magnetometer and a light reflector, used to measure the local magnetic field strength and the distance of the Moon to the Earth.

The corner cube array (the "light reflector") is insufficient for getting returns from the Earth and measuring the distance.
It is supplied by NASA to be part of a navigation system for lunar orbit.
As such, it's not a science experiment.

However, the question your response is attempting to answer is plausible but not compelling.  It's a matter of taste and opinion. 
There is a little science here, but not much commerce, as nothing is being sold.   
It's not a sponsored by the Israeli government, so it doesn't belong in a national thread. 
So if this discussion doesn't fit perfectly here, it doesn't clearly fit better anywhere else. 
And further discussing it is a distraction from a fascinating mission. 
However, if mlinder wants to start a new thread about Beresheet in another area, only the mods can stop him.
What kind of wastrels would dump a perfectly good booster in the ocean after just one use?

Offline Comga

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Re: Spaceil Israeli Moon mission
« Reply #52 on: 02/26/2019 04:51 am »
Are there any details available on the issue with the star trackers?
Wondering if the trackers are just impaired, or maybe out of commission?
It's not uncommon for star trackers to have baffle problems which cause them to not work when pointed closer to the sun than some critical angle.  Hopefully they have another differently-oriented tracker they can switch to, or the flexibility to reorient the spacecraft, to work around this issue.

Most optical space instruments have "Solar Keep Out Angles", a cone about the line of sight that if it includes the Sun, will disrupt operations. 
There are a few facilities that can really measure the off axis performance, the exact angle at which these levels are exceeded and the operations are disrupted. 
This can require the irradiance on the focal plane to be billionths or trillionths of the solar irradiance. 
It's really hard to get a room dark enough to not let source light leak into the path and affect the test. 
So sometimes, light baffling doesn't work as planned, and the failures escape detection.
I can think of a major instrument, built at a NASA center, costing much more than the entire Beresheet mission, that lost one of its two channels to light leak not detected in ground testing. 
This stuff is difficult.
But as ccdengr said, they will have to find a way around it, alternative orientations or using an IMU to off-point where solar intrusion is anticipated.  It would be interesting to know how they solve this.
And the recent system upset....
What kind of wastrels would dump a perfectly good booster in the ocean after just one use?

Offline Lar

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Re: Spaceil Israeli Moon mission
« Reply #53 on: 02/26/2019 06:28 am »
Long time posters know that the way to ask for a move to a different area is report to mod. Not posting. I don't see any compelling reason to move it.
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Offline lamid

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Re: Spaceil Israeli Moon mission
« Reply #54 on: 02/26/2019 08:52 am »
https://www.jewishpress.com/news/science-and-tech/beresheet-cancels-maneuver-in-space-following-technical-malfunction/2019/02/26/

The Israeli spacecraft Beresheet canceled a maneuver in space following a technical malfunction.
“The engineering teams of SpaceIL and IAI are examining the data and analyzing the situation. At this time, the spacecraft’s systems are working well, except for the known problem in the star tracker.”

“The control center has contact with the spacecraft according to plan and it continues its previous orbit until the next maneuver. We will update the planned schedule later,” the statement concluded.

Offline lamid

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Offline mcgyver

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Re: Spaceil Israeli Moon mission
« Reply #56 on: 02/26/2019 03:03 pm »
If I understand correctly raw data of this file, Beresheet is going to "upgrade" its orbit this night, raising apogee from 74000 to 120000 km:
25/02/2019 9.54 -  74140km
26/02/2019 20.49 - 121232km

Next raisings:
10/3: 276000 km
25/3: 391000 km

Source: http://live.spaceil.com/
« Last Edit: 02/26/2019 03:06 pm by mcgyver »

Offline mcgyver

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Re: Spaceil Israeli Moon mission
« Reply #57 on: 02/26/2019 03:14 pm »
Ops...



Quote
Feb. 26 – Last night at around 12 a.m. Israel time, another maneuver was planned for Beresheet as it passed near Earth, in an area without communication.


During the pre-maneuver phase the spacecraft computer reset unexpectedly, causing the maneuver to be automatically cancelled.




The engineering teams of SpaceIL and IAI are examining the data and analyzing the situation. At this time, the spacecraft’s systems are working well, except for the known problem in the star tracker.


Communication between the control center and the spacecraft remains as planned, and Beresheet continues its previous orbit until the next maneuver. We will continue to provide updates regularly.
(from the redundant thread)


This is a good chance to check if the raw files are updated.
« Last Edit: 02/26/2019 03:15 pm by mcgyver »

Offline Lar

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Re: Spaceil Israeli Moon mission
« Reply #58 on: 02/26/2019 04:50 pm »
Chris yelled at himself for that :)

Normally we don't separate things this way but this mission doesn't belong in a launcher thread.
"I think it would be great to be born on Earth and to die on Mars. Just hopefully not at the point of impact." -Elon Musk
"We're a little bit like the dog who caught the bus" - Musk after CRS-8 S1 successfully landed on ASDS OCISLY

Online TrevorMonty

Re: Spaceil Israeli Moon mission
« Reply #59 on: 02/26/2019 05:05 pm »
There is some pluses to taking slow route to moon. Plenty of time to find bugs and sort them out before critical landing.

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