Geekzone: technology news, blogs, forums
Guest
Welcome Guest.
You haven't logged in yet. If you don't have an account you can register now.




Glurp
9512 posts

Uber Geek
+1 received by user: 4508

Subscriber

Topic # 243275 4-Dec-2018 10:02
Send private message

Who here is an astrophysicist? I am reading about the OSIRIS-REx probe sent to Bennu. Because the gravity is so low, it is difficult to keep the probe in orbit. My question is, why bother? Would it not be simpler to just let the probe bump down onto the asteroid after doing a photo survey on approach? They have to match speeds anyway and I would think it would be easier just to let gravity join it up with the asteroid rather than try to stay in orbit. When it is time to leave, it shouldn't be difficult to achieve escape velocity. Can someone explain this please?

 

 





I reject your reality and substitute my own. - Adam Savage
 


Filter this topic showing only the reply marked as answer Create new topic
4033 posts

Uber Geek
+1 received by user: 1352


  Reply # 2139051 4-Dec-2018 10:16
One person supports this post
Send private message

Brian May would be the coolest astrophysicist around... hopefully he reads gz :)

 

I don't think it is as easy to touch down as you think. Wildly undulating surfaces, caves, gas explosions and fissures, unpredictable gravity field would confuse the concept of up and down.   Cos, you have to set down at a location and orientation where you can still get power and communicate back home. 

 

Did you see armageddon? I like to think this is how it might be. 




Glurp
9512 posts

Uber Geek
+1 received by user: 4508

Subscriber

  Reply # 2139057 4-Dec-2018 10:24
Send private message

You are thinking of a comet. Asteroids are much quieter.

 

 





I reject your reality and substitute my own. - Adam Savage
 


 
 
 
 


13843 posts

Uber Geek
+1 received by user: 6606

Trusted
Subscriber

  Reply # 2139063 4-Dec-2018 10:31
Send private message

It makes soft contact with the surface and will return to with a sample circa 2023





Mike
Retired IT Manager. 
The views stated in my posts are my personal views and not that of any other organisation.

 

Using empathy takes no energy and can gain so much. Try it.

 

 


15358 posts

Uber Geek
+1 received by user: 2984
Inactive user


  Reply # 2139065 4-Dec-2018 10:35
Send private message

surfisup1000:

 

Brian May would be the coolest astrophysicist around... hopefully he reads gz :)

 

I don't think it is as easy to touch down as you think. Wildly undulating surfaces, caves, gas explosions and fissures, unpredictable gravity field would confuse the concept of up and down.   Cos, you have to set down at a location and orientation where you can still get power and communicate back home. 

 

Did you see armageddon? I like to think this is how it might be. 

 

 

Brian Cox you mean?


15358 posts

Uber Geek
+1 received by user: 2984
Inactive user


  Reply # 2139096 4-Dec-2018 10:40
Send private message

Ah the Queen guy, and he got a PhD is Astrophysics as well! And one named after him, so yes, that pretty cool


707 posts

Ultimate Geek
+1 received by user: 200


  Reply # 2139102 4-Dec-2018 10:43
Send private message

Brian May from Queen (the Band) has to be much cooler than any other Brian :)




Glurp
9512 posts

Uber Geek
+1 received by user: 4508

Subscriber

  Reply # 2139152 4-Dec-2018 11:08
Send private message

Way to stay on topic guys.

 

 





I reject your reality and substitute my own. - Adam Savage
 


3682 posts

Uber Geek
+1 received by user: 1092


  Reply # 2139156 4-Dec-2018 11:17
Send private message

Rikkitic:

 

Who here is an astrophysicist? I am reading about the OSIRIS-REx probe sent to Bennu. Because the gravity is so low, it is difficult to keep the probe in orbit. My question is, why bother? Would it not be simpler to just let the probe bump down onto the asteroid after doing a photo survey on approach? They have to match speeds anyway and I would think it would be easier just to let gravity join it up with the asteroid rather than try to stay in orbit. When it is time to leave, it shouldn't be difficult to achieve escape velocity. Can someone explain this please?

 

 

The fact they are going to spend 18 months orbiting the rock to determine the landing site, makes me think that a photo survey on approach would not get them anywhere near the level of detail that the survey team require to determine their sample site...


4697 posts

Uber Geek
+1 received by user: 2644

Trusted

  Reply # 2139165 4-Dec-2018 11:33
Send private message

They need to watch The Empire Strikes Back. Han Solo managed to land on an asteroid no problemo. Just watch out for space ship eating slugs.


7997 posts

Uber Geek
+1 received by user: 4338


  Reply # 2139213 4-Dec-2018 12:30
One person supports this post
Send private message

Gravity is so low - ten millionths of the surface gravity of earth.

 

AFAIK, it's not "landing" in a conventional sense, but reducing orbit until it's close enough to move in and for a robotic arm to grab a sample, then it "bounces off".  There's enough propellant for 3 attempts.

 

If the mass of the spacecraft is 1500kg (a guess with fuel), then the "weight" of the spacecraft on the surface of the asteroid is only about 15 grams, so if the contact with the arm on the surface was to hit an object and be deflected/lose control, it might possibly spin, bounce off the asteroid and not be able to complete the mission.


1324 posts

Uber Geek
+1 received by user: 155


  Reply # 2139215 4-Dec-2018 12:36
Send private message

At a guess I would start with a 3 body differential equation.

My thinking is, one would need to calculate the orbit of the asteroid in reference to a known observation point using something like the gausian method.

One could then calculate the required orbit of the satelite and factor in the need to alow it down and adjust its approach angle I suspect to get it to fall into orbit.

I think to get it to land on the asteroid, one would need to something like the above, then add a rocket motor and a bunch of other equipment to get it to land (crash) in a controlled manner.





Software Engineer

 




Glurp
9512 posts

Uber Geek
+1 received by user: 4508

Subscriber

  Reply # 2139216 4-Dec-2018 12:40
Send private message

That sounds fairly convincing. I was thinking that if they can control the probe precisely enough to keep it in orbit around such a low mass object (apparently that needs constant corrections), why not just match trajectories (surely no more difficult) until it just gently settles down. Gravity would be sufficient to draw it to the surface and keep it there if no other forces were acting on it. Once landed it wouldn't have to keep being adjusted since gravity would hold it in place. Still easy to take off again later. It doesn't land as such, it just eases in until contact is made. If that is done sufficiently gently, it won't bounce. But what you say also makes sense.

 

Edit: reply was to Fredd99

 

 

 

 

 

 

 

 





I reject your reality and substitute my own. - Adam Savage
 


Filter this topic showing only the reply marked as answer Create new topic


Donate via Givealittle


Twitter »

Follow us to receive Twitter updates when new discussions are posted in our forums:



Follow us to receive Twitter updates when news items and blogs are posted in our frontpage:



Follow us to receive Twitter updates when tech item prices are listed in our price comparison site:





News »

Amazon introduces new Kindle with adjustable front light
Posted 21-Mar-2019 20:14


A call from the companies providing internet access for the great majority of New Zealanders, to the companies with the greatest influence over social media content
Posted 19-Mar-2019 15:21


Two e-scooter companies selected for Wellington trial
Posted 15-Mar-2019 17:33


GeForce GTX 1660 available now
Posted 15-Mar-2019 08:47


Artificial Intelligence to double the rate of innovation in New Zealand by 2021
Posted 13-Mar-2019 14:47


LG demonstrates smart home concepts at LG InnoFest
Posted 13-Mar-2019 14:45


New Zealanders buying more expensive smartphones
Posted 11-Mar-2019 09:52


2degrees Offers Amazon Prime Video to Broadband Customers
Posted 8-Mar-2019 14:10


D-Link ANZ launches D-Fend AC2600 Wi-Fi Router Protected by McAfee
Posted 7-Mar-2019 11:09


Slingshot commissions celebrities to design new modems
Posted 5-Mar-2019 08:58


Symantec Annual Threat Report reveals more ambitious, destructive and stealthy attacks
Posted 28-Feb-2019 10:14


FUJIFILM launches high performing X-T30
Posted 28-Feb-2019 09:40


Netflix is killing content piracy says research
Posted 28-Feb-2019 09:33


Trend Micro finds shifting threats require kiwis to rethink security priorities
Posted 28-Feb-2019 09:27


Mainfreight uses Spark IoT Asset Tracking service
Posted 28-Feb-2019 09:25



Geekzone Live »

Try automatic live updates from Geekzone directly in your browser, without refreshing the page, with Geekzone Live now.


Support Geekzone »

Our community of supporters help make Geekzone possible. Click the button below to join them.

Support Geezone on PressPatron



Are you subscribed to our RSS feed? You can download the latest headlines and summaries from our stories directly to your computer or smartphone by using a feed reader.

Alternatively, you can receive a daily email with Geekzone updates.