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Old 04-11-2019, 04:02 PM
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The Moon is a harsh mistress [Beresheet failure]


The first private attempt of a soft landing on the moon made a much harder impact.
They successfully got the lander in orbit and things were going well until the main engine had issues (I 3watched teh webcast but I'm not 100% sure of the timeline. i think they lost/regained telemetry before the engine issue)

They managed to restart thge main engine but it was too little too late
https://arstechnica.com/science/2019...ding-thursday/

I do hope we get a detailed analysis.

Ad Astra per Aspera,
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Old 04-11-2019, 04:11 PM
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The engine failed and the lander crashed, or did the engine explode at altitude?
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Old 04-11-2019, 04:18 PM
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Quote:
Originally Posted by Jason Davis
After what appeared to be a flawless initial descent, mission controllers announced Beresheet had a problem with its main engine. Real-time telemetry provided by SpaceIL showed the spacecraft was descending too quickly for its low altitude, and though the team was eventually able to restart the engine, it was too late.
http://www.planetary.org/blogs/jason...e-crashes.html

Brian
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Old 04-11-2019, 04:32 PM
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It's frustrating that so much of the mission was successful, and it apparently failed due to one glitch in the final moments, causing it to impact the moon at nearly 300 mph. After the failure of the ESA Mars lander a few years ago, it makes one appreciative of the marvelous things that NASA has done successfully. To be fair, enormous budgets are helpful. Even the "cheap" New Horizons mission cost $700-$900 million depending on who you believe, and the Curiosity rover cost $2.5-$2.8 billion.
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Old 04-11-2019, 04:38 PM
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That's Hebrew for "In the beginning", right?
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Old 04-11-2019, 04:41 PM
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That's Hebrew for "In the beginning", right?
That's what it means. (It is the first word of "Genesis")

Last edited by DPRK; 04-11-2019 at 04:41 PM.
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Old 04-11-2019, 04:50 PM
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Of course now they'll have to rename it "Ohsheet."
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Old 04-11-2019, 04:57 PM
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Apparently they already had a contract. Not sure if that is permanently scuttled now, or if a deal is a deal?
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Old 04-11-2019, 04:58 PM
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^ +1 (to Darren Garrison)

(that was really good!)


~VOW

Last edited by VOW; 04-11-2019 at 04:59 PM.
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Old 04-11-2019, 05:17 PM
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Well, dang. Sorry to hear about that, Israeli people!

Yet Another Reminder of why "rocket science" has entered the lexicon to mean "complicated and really hard to do".
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Old 04-11-2019, 06:27 PM
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Originally Posted by wolfpup View Post
After the failure of the ESA Mars lander a few years ago, it makes one appreciative of the marvelous things that NASA has done successfully.
NASA has had some spectacular failures.

I recall hearing once that only half of attempted Mars missions make it, whether to orbit or landing, and that's inclusive of everyone who's ever tried it.

NASA had a spaceship catch fire on the ground and kill three people (Apollo 1), two space shuttles that came to grief, and its share of crashed probes and the like.

The USSR had its share of failures, too.

Space is HARD.

The folks behind this mission should be applauded - successfully getting to Moon orbit is an achievement. I hope they try again.
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Old 04-11-2019, 10:55 PM
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From my Hebrew speaking/reading friend:

The Hebrew language publications are writing that the initial analysis points to a failure of one of the accelerometers (IMU2), which seems to have provided incorrect data and caused the main engine to turn off prematurely.

At an altitude of 150 m the spacecraft was still doing 150 m/s or 335 mph.

They're also noting that at such a high speed, the spacecraft likely created an impact crater 3 to 5 m in diameter, which means it should be visible from a lunar orbiter. Perhaps we will see a photo soon of the crash site.
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Old 04-11-2019, 11:20 PM
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Why would a single accelerometer be critical? Weren't there at least a couple more? And couldn't you derive your acceleration from the radar altitude, for instance, in a fail-safe situation in which less data than normal is available to estimate your system state (shutting down your engine way up high does not seem like optimal control in any case, even if you lose all instruments and have to extrapolate from your last known position and velocity).
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Old 04-12-2019, 02:01 AM
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Well, dang. Sorry to hear about that, Israeli people!
Thanks. It was not a fun experience, watching it live last night with my family. My son - who's into space - was crying a bit, and I needed a few shots of bourbon myself to avoid joining him. Oh well.

We'll do better next time.
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Old 04-12-2019, 02:31 AM
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Thanks. It was not a fun experience, watching it live last night with my family. My son - who's into space - was crying a bit, and I needed a few shots of bourbon myself to avoid joining him. Oh well.

We'll do better next time.
The US and the USSR had a lot of failures before any of us succeeded. And neither the Soviets nor the Americans even tried to land things on the Moon until they had perfected the art of crashing things into the Moon. Including attempts to crash into the Moon, that wound up missing the entire Moon.
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Old 04-12-2019, 12:11 PM
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Originally Posted by MEBuckner View Post
Well, dang. Sorry to hear about that, Israeli people!

Yet Another Reminder of why "rocket science" has entered the lexicon to mean "complicated and really hard to do".

Dammit, Smithers, this isn't rocket science, it's brain surgery. Now hand me that ice cream scoop.
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Old 04-12-2019, 12:25 PM
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Wisdom from my brother: Beresheet is a fitting name, because you always make mistakes in the beginning.

Hopefully, the next one will go better.
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Old 04-12-2019, 12:41 PM
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Quote:
Originally Posted by MEBuckner View Post
The US and the USSR had a lot of failures before any of us succeeded. And neither the Soviets nor the Americans even tried to land things on the Moon until they had perfected the art of crashing things into the Moon. Including attempts to crash into the Moon, that wound up missing the entire Moon.
Pretty good pep talk, actually. The Beresheet people just need to retroactively define this as a "crash it into the moon" mission that almost failed into a "soft landing on the moon".
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Old 04-12-2019, 09:55 PM
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Quote:
Originally Posted by N9IWP View Post
From my Hebrew speaking/reading friend:

The Hebrew language publications are writing that the initial analysis points to a failure of one of the accelerometers (IMU2), which seems to have provided incorrect data and caused the main engine to turn off prematurely.

At an altitude of 150 m the spacecraft was still doing 150 m/s or 335 mph.

They're also noting that at such a high speed, the spacecraft likely created an impact crater 3 to 5 m in diameter, which means it should be visible from a lunar orbiter. Perhaps we will see a photo soon of the crash site.
This is not the first spacecraft named "Genesis" that had landing problems because of accelerometers:

Quote:
Originally Posted by Wikipedia
Due to a design flaw in a deceleration sensor, parachute deployment was never triggered, and the spacecraft's descent was slowed only by its own air resistance. The planned mid-air retrieval could not be carried out, and the capsule crashed into the desert floor of the Dugway Proving Ground in Tooele County, Utah, at about 86 meters per second (311 km/h (193 mph)).
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Old 04-13-2019, 12:01 AM
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In space flight, expecting engines, guidance, and communication systems to perform absolutely perfectly is a fantasy. (While it was a complicated chain of events, the recent airplane disaster illustrates all too well the dangers of automated systems relying on single sensors.) I understand that the point of this lunar lander demonstrator was to be as cheap as possible, but the technology was intended to deliver future scientific payloads to the moon's surface, and in that case you absolutely need procedures to recover, to the extent possible, from various systems failures.

I wonder if the recent failure was due to something as simple as a programming error? Even outside of amateur hour, plenty of space vehicles have been lost that way (Climate Orbiter, Ariane, Mariner, etc) and the procedures to minimize such risks are not trivial.

Since the namers of this spacecraft insist on Biblical references: "And they said, Go to, let us build us a city and a tower, whose top may reach unto heaven; and let us make us a name, lest we be scattered abroad upon the face of the whole earth. And the Lord came down to see the city and the tower, which the children of men builded. And the Lord said, Behold, the people is one, and they have all one language; and this they begin to do: and now nothing will be restrained from them, which they have imagined to do. Go to, let us go down, and there confound their language, that they may not understand one another's speech. So the Lord scattered them abroad from thence upon the face of all the earth: and they left off to build the city."

Last edited by DPRK; 04-13-2019 at 12:02 AM.
  #21  
Old 04-13-2019, 12:49 AM
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Why would a single accelerometer be critical? Weren't there at least a couple more?
Well, my guess is that there are 2 factors:
1) every bit of excess mass must be eliminated in space, and
2) they were doing it as cheap as possible.

If it turns out that a 2nd one would have saved the mission, then it is NOT excess, and that not including it was a very expensive wrong decision. But that often happens when doing things for the first time.
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Old 04-14-2019, 05:44 PM
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Quote:
Originally Posted by Alessan View Post
Thanks. It was not a fun experience, watching it live last night with my family. My son - who's into space - was crying a bit, and I needed a few shots of bourbon myself to avoid joining him. Oh well.

We'll do better next time.
I'm sorry it happened, but you're right: there will be a next time!

Alessan, you might want to share this quotation with your son:

Quote:
Originally Posted by John F Kennedy
We choose to go to the moon in this decade and do the other things, not because they are easy, but because they are hard; because that goal will serve to organize and measure the best of our energies and skills, because that challenge is one that we are willing to accept...
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Old 04-23-2019, 07:38 AM
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More info:
http://www.planetary.org/blogs/jason...beresheet.html

The command to fix the faulty IMU somehow caused a cascading failure.

Brian
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Old 04-23-2019, 01:42 PM
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Thanks for the update. We'll have to wait for the promised report, but it sure sounds like software or programming error. Interesting that they also felt the need to remotely reboot various subsystems in the middle of landing while also subject to spotty comms (and that there was no backup to withstand a "cascading failure").

Now, apparently a bunch of NASA space probes and Mars missions have used VxWorks as a computer operating system for their platform. What hardware and software do SpaceIL use? How about SpaceX? What are the various "industry standards", if any?

ETA: This discussion suggests that SpaceX has adopted some form of Linux[/url]

Last edited by DPRK; 04-23-2019 at 01:47 PM.
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Old 04-24-2019, 04:51 PM
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Linux. Because BSOD in Space is a bad thing...
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  #26  
Old 04-24-2019, 08:55 PM
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Some info on the (SpaceX) hardware:
Quote:
SpaceX uses an Actor-Judge system to provide triple redundancy to its rockets and spacecraft. The Falcon 9 has 3 dual core x86 processors running an instance of linux on each core. The flight software is written in C/C++ and runs in the x86 environment. For each calculation/decision, the "flight string" compares the results from both cores. If there is a inconsistency, the string is bad and doesn't send any commands. If both cores return the same response, the string sends the command to the various microcontrollers on the rocket that control things like the engines and grid fins.

The microcontrollers, running on PowerPC processors, received three commands from the three flight strings. They act as a judge to choose the correct course of actions. If all three strings are in agreement the microcontroller executes the command, but if 1 of the 3 is bad, it will go with the strings that have previously been correct. The Falcon 9 can successfully complete its mission with a single flight string.

The triple redundancy gives the system radiation tolerance without the need for expensive rad hardened components. SpaceX tests all flight software on what can be called a table rocket. They lay out all the computers and flight controllers on the Falcon 9 on a table and connect them like they would be on the actual rocket. They then run a complete simulated flight on the components, monitoring performance and potential failures.

SpaceX engineers perform what they call "Cutting the strings" where they randomly shut off a flight computer mid simulation, to see how it responds.

Dragon uses a similar triple redundant system for its flight computers.
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Old 05-15-2019, 08:02 PM
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The splatting site has been found.
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