IPB

Welcome Guest ( Log In | Register )

2 Pages V  < 1 2  
Reply to this topicStart new topic
Orbiter missions with no (or little) fuel usage for deceleration, Target planet capturing the spacecraft w/o extensive fuel usage
djellison
post Sep 1 2015, 10:58 PM
Post #16


Administrator
****

Group: Chairman
Posts: 14018
Joined: 8-February 04
Member No.: 1



QUOTE (HSchirmer @ Sep 1 2015, 01:15 PM) *
Getting a stable circular orbit around an outer planet it energy intensive.


Indeed. The examples I cited ( MRO, Cassini, Galileo, MESSENGER, Uranus orbiter ) almost all end in exceptionally eccentric orbits - they are pretty much the minimum delta V you could possibly use whilst remaining gravitationally bound to the spacecraft. MESSENGER wasn't hugely excentric - but far from circular. It's already highly energy intensive to get into ANY orbit - let alone a circular one.

in the case of Cassini and Galileo, multiple gravity assists from moons were used to manipulate the orbit thereafter.

In the case of MRO - it's aerobraking that makes up the difference.


The spare NRO hardware equates to enough hardware for one telescope. It's to be used as the basis for the proposed WFIRST mission. Getting a spacecraft that massive ( >11 tons ) into some sort of orbital tour of Mars, asteroids and the outer solar system would require extraordinary amounts of Delta V that would pretty much require next gen solar-electric prop ( which obviously isn't going to work beyond Jovian like distances )
Go to the top of the page
 
+Quote Post
HSchirmer
post Sep 2 2015, 02:19 AM
Post #17


Member
***

Group: Members
Posts: 277
Joined: 24-July 15
Member No.: 7619



QUOTE (djellison @ Sep 1 2015, 11:58 PM) *
Getting a spacecraft that massive ( >11 tons ) into some sort of orbital tour of Mars, asteroids and the outer solar system
would require extraordinary amounts of Delta V that would pretty much require next gen solar-electric prop


Correct. Except when it isn't.

The beauty of chaotic orbits that require little to no delta-v is that 0 x anything = 0
Zero x 350kg craft = zero thrust.
Zero x 11 ton craft = zero thrust.

http://www2.esm.vt.edu/~sdross/talks/ross-csulb-2003.pdf
http://forum.nasaspaceflight.com/index.php?topic=26217.0

Idea is, old spy satellite and icbm components could be reporposed into a group of space telescopes.
If we aren't using them to spy on each other, might as well send them out to get pictures of other planets and moons.

Take a spy satellite telescope, add a Dawn style ion engine powered by a RTG, and a big antenna to transmit back to earth.
Send it out to Earth's L2 point, then let it traverse the roughly zero-delta-v chaotic orbit pathways from earth's L2 out to the gas giants and beyond.
While it is in-between planets, telescope could look at stars and galaxies just like hubble.
But when it closes in on planetary sytems, we get great images of planets, moons etc.
That takes lots of time, but, if the telescope does science on the way out, who cares as long as our kids and grand-kids get great photos?

Attached thumbnail(s)
Attached Image
Attached Image
 
Go to the top of the page
 
+Quote Post
HSchirmer
post Sep 2 2015, 02:56 AM
Post #18


Member
***

Group: Members
Posts: 277
Joined: 24-July 15
Member No.: 7619



Cool map, with classical transfer orbit delta-v

http://www.dailymail.co.uk/sciencetech/art...solar-Tube.html

Cooler map, with chaotic minimal delta-v
http://www.gg.caltech.edu/~mwl/publication...SAndOrigins.pdf
Attached thumbnail(s)
Attached Image
Attached Image

 
Go to the top of the page
 
+Quote Post
djellison
post Sep 2 2015, 03:11 PM
Post #19


Administrator
****

Group: Chairman
Posts: 14018
Joined: 8-February 04
Member No.: 1



QUOTE (HSchirmer @ Sep 1 2015, 07:19 PM) *
Zero x 350kg craft = zero thrust.
Zero x 11 ton craft = zero thrust.


You say zero thrust - then talk about an RTG powered Dawn Thruster.

Dawn's thrusters require approx 10x the output of a typical RTG. Also - assuming you could apply every ounce of Delta V that Dawn has generated and apply it to a Hubble sized payload, the total Delta-V it would impart would drop from approx 10km/sec to 1.4 or so.

Exploring the Earth-Moon region with little Delta-V is easy. It's been done time and again. That Scientific American article is somewhat disingenuous to talk about the '300 million miles' that Genesis traveled....when it actually just went to L1 and back, via L2... in an geocentric frame, a few million miles, not hundreds of millions. It also negates the fact that getting from LEO to L1 requires >3.5km/sec in the first place.

Getting out to Mars, Jupiter, Saturn and beyond....I see no reference to the zero Delta-V trajectories in either of the papers you cite.

I'd be delighted to see a realistic trajectory that gets 11 tons from LEO or even L1 to Mars, Jupiter and beyond with zero delta V in a time frame realistic for the lifetime of a spacecraft. Say, 10-20 years.
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: 17th October 2017 - 03:11 PM
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.