IPB

Welcome Guest ( Log In | Register )

2 Pages V  < 1 2  
Reply to this topicStart new topic
Asteroid Grand Tour
nprev
post Apr 8 2007, 06:07 PM
Post #16


Senior Member
****

Group: Moderator
Posts: 7002
Joined: 8-December 05
From: Los Angeles
Member No.: 602



Yeah...seems as if the prime filter would be choosing specific asteroids of given types, then running optimization NLPs on that set & comparing it to others. Not a trivial problem at all...I just survived two quarters of numerical systems optimization, can really appreciate the work that went into this effort!


--------------------
A few will take this knowledge and use this power of a dream realized as a force for change, an impetus for further discovery to make less ancient dreams real.
Go to the top of the page
 
+Quote Post
Greg Hullender
post Apr 8 2007, 07:11 PM
Post #17


Senior Member
****

Group: Members
Posts: 1010
Joined: 29-November 05
From: Seattle, WA, USA
Member No.: 590



With only four asteroids, I don't the choice of the order in which to visit them adds much to the difficulty of the problem. Even the travelling-salesman problem is easy to solve with 4 (or even 10) cities, just by exhaustive search.

Which is not to say it's an easy problem overall, of course. :-)

--Greg
Go to the top of the page
 
+Quote Post
nprev
post Apr 9 2007, 12:53 AM
Post #18


Senior Member
****

Group: Moderator
Posts: 7002
Joined: 8-December 05
From: Los Angeles
Member No.: 602



I think things like minimizing propellant consumption & transit times might add more complexity that you'd think at first glance, Greg, combined with the fact that they're apparently not looking at four pre-selected "hard targets" but instead trying to choose from (presumably) thousands of four compositional categories. Not the way I'd necessarily do it as I said in my previous post, but that's probably how most of the teams will approach the problem in order to try to find a truly optimal solution (they probably have some major processing capability and the latest in solvers, after all... smile.gif )


--------------------
A few will take this knowledge and use this power of a dream realized as a force for change, an impetus for further discovery to make less ancient dreams real.
Go to the top of the page
 
+Quote Post
Floyd
post Apr 9 2007, 01:44 AM
Post #19


Member
***

Group: Members
Posts: 622
Joined: 4-September 06
From: Boston
Member No.: 1102



Greg, you are correct in that the traveling salesman problem is trivial for 4 cities--can be solved exactly with ease. However, in the asteroid tour, you don't know which asteroids you will visit, only that you will visit one of each of four kinds. Thus you have to find the most efficient way to get to four line up asteroids of the four different kinds out of the thousands all dancing around. The cities are moving and you won't know their names until you have your solution. biggrin.gif


--------------------
Floyd
Go to the top of the page
 
+Quote Post
Greg Hullender
post Apr 9 2007, 03:15 AM
Post #20


Senior Member
****

Group: Members
Posts: 1010
Joined: 29-November 05
From: Seattle, WA, USA
Member No.: 590



As I said, it's not an easy problem, but that's not because it's anything like the Travelling-Salesman problem.

--Greg
Go to the top of the page
 
+Quote Post
tasp
post Apr 9 2007, 01:59 PM
Post #21


Member
***

Group: Members
Posts: 885
Joined: 30-January 05
Member No.: 162



Has anyone gone back and looked at the Voyager paths through the asteroid belt? Did they plausibly get close to anything?

(keeping in mind the tremendous number of asteroids discovered since the 70s, is it most likely anything they got close to was unknown at the time?)
Go to the top of the page
 
+Quote Post
nprev
post Apr 9 2007, 02:44 PM
Post #22


Senior Member
****

Group: Moderator
Posts: 7002
Joined: 8-December 05
From: Los Angeles
Member No.: 602



QUOTE (monitorlizard @ Apr 9 2007, 06:25 AM) *
A couple of years ago I read that Dawn might flyby six or more asteroids during its mission because of all its extra delta-V.


Hmm. Wonder if this activity is actually intended to design an extended mission for Dawn.


--------------------
A few will take this knowledge and use this power of a dream realized as a force for change, an impetus for further discovery to make less ancient dreams real.
Go to the top of the page
 
+Quote Post
tedstryk
post Apr 17 2007, 03:35 PM
Post #23


Interplanetary Dumpster Diver
****

Group: Moderator
Posts: 4214
Joined: 17-February 04
From: Powell, TN
Member No.: 33



I think they were more thinking about tweaking its trajectory to take advantage of serendipitous flyby when it is in the asteroid belt but not studying Vesta or Ceres.


--------------------
Go to the top of the page
 
+Quote Post
JRehling
post Apr 17 2007, 04:40 PM
Post #24


Senior Member
****

Group: Members
Posts: 1572
Joined: 20-April 05
Member No.: 321



QUOTE (nprev @ Apr 8 2007, 08:07 AM) *
It may be that some variation of JR's idea was explored by some of the teams in this year's trajectory optimization competition, but their focus seems to be on deriving planetary "pump-up" gravitational assists. If I'm visualizing this correctly, such assists cannot occur for a spacecraft in a retrograde orbit?... huh.gif


I think my idea fails the listed criteria, because zooming out to 5.2 AU is bound to take more time up front than a mission that follows a more Dawnlike trajectory. And it's probably more costly, too. But it would visit a lot more asteroids. I'd like to see teams concoct the most productive tours in a retrograde orbit. Honestly, if you had a craft with a long lifespan and you did nothing but wait for serendipitous flybys, it seems like dozens would be possible -- maybe one every eight months for 20 years or so. My idea is just plain "bigger" than the stated contest asks for.

It would be exciting to see, though, what a shrewd plan could accomplish, looking ahead like Deep Blue to find the cleverest mission. Could 30 flybys be possible? 50?
Go to the top of the page
 
+Quote Post
JKreider
post Sep 29 2009, 07:20 PM
Post #25


Newbie
*

Group: Members
Posts: 1
Joined: 24-December 08
Member No.: 4515



Retrograde Asteroid Fly-by Trajectories, RAFT

I've spent quite a bit of time on this problem and my conclusion is that the time it requires is more of an issue than the delta-V. Attached are Phase I and II orbit diagrams for a RAFT mission. A candid summary of my work is online at:
Jaqar Astrodynamics Forum

Comments are welcome.

Attached Image


Attached Image
Go to the top of the page
 
+Quote Post
SFJCody
post Sep 29 2009, 07:44 PM
Post #26


Member
***

Group: Members
Posts: 777
Joined: 8-February 04
From: Arabia Terra
Member No.: 12



Very interesting work. I wonder if it would be worthwhile for such a spacecraft to carry small impactors. They wouldn't need to have that much mass what with the huge velocity differences involved.
Go to the top of the page
 
+Quote Post
Holder of the Tw...
post Sep 29 2009, 09:10 PM
Post #27


Member
***

Group: Members
Posts: 390
Joined: 17-November 05
From: Oklahoma
Member No.: 557



Such impactors would be excellent for spectral studies, but you wouldn't be sticking around for very long to study the crater.
Go to the top of the page
 
+Quote Post

2 Pages V  < 1 2
Reply to this topicStart new topic

 



RSS Lo-Fi Version Time is now: 2nd September 2014 - 04:24 AM
RULES AND GUIDELINES
Please read the Forum Rules and Guidelines before posting.

IMAGE COPYRIGHT
Images posted on UnmannedSpaceflight.com may be copyrighted. Do not reproduce without permission. Read here for further information on space images and copyright.

OPINIONS AND MODERATION
Opinions expressed on UnmannedSpaceflight.com are those of the individual posters and do not necessarily reflect the opinions of UnmannedSpaceflight.com or The Planetary Society. The all-volunteer UnmannedSpaceflight.com moderation team is wholly independent of The Planetary Society. The Planetary Society has no influence over decisions made by the UnmannedSpaceflight.com moderators.
SUPPORT THE FORUM
Unmannedspaceflight.com is a project of the Planetary Society and is funded by donations from visitors and members. Help keep this forum up and running by contributing here.