IPB

Welcome Guest ( Log In | Register )

Will aerocapture work for a Jupiter orbiter/moon lander?
Guest_Zvezdichko_*
post Feb 9 2007, 04:33 PM
Post #1





Guests






This is something interesting. But knowing the harsh radiation environment of the giant, I don't know whether it could be used at all. I suppose that a plunge into the atmosphere then achieving a trajectory which leads to a direct encounter with a moon could be used for a lander... Or for a long-living orbiter.
Go to the top of the page
 
+Quote Post
2 Pages V   1 2 >  
Start new topic
Replies (1 - 14)
JRehling
post Feb 9 2007, 05:42 PM
Post #2


Senior Member
****

Group: Members
Posts: 1571
Joined: 20-April 05
Member No.: 321



QUOTE (Zvezdichko @ Feb 9 2007, 08:33 AM) *
This is something interesting. But knowing the harsh radiation environment of the giant, I don't know whether it could be used at all. I suppose that a plunge into the atmosphere then achieving a trajectory which leads to a direct encounter with a moon could be used for a lander... Or for a long-living orbiter.


Radiation should not be a problem: The harm that radiation does is integrated over time, and a quick pass through Jupiter's radiation belts on a single pass would only accumulate a small fraction of the radiation damage that Galileo encountered. The Galileo Entry Probe passed, obviously, through all of Jupiter's radiation belts once with no harmful effects. An aerocapture craft would simply do so twice. The question would be how much more radiation it had to absorb during the rest of its mission. The first few hours wouldn't be the concern.

The idea of a lander for Io or Europa that utilized aerobraking is quite interesting. Ideally, the craft would leave Jupiter's atmosphere with just enough velocity to kiss the orbit of the target moon. Then a powered descent would have similar delta-v requirements to that for a lander headed towards Earth's Moon. Some combination between powered descent and a penetrator could also be apt. In one ideal design, you could have a craft ride ballistically all the way from launch to penetration into the surface of Europa -- I wonder if the specs would work out on that?

Note that the minimum-energy departure from Jupiter would mean a slower pass through the radiation belts, and then the accumulated radiation exposure could be significant. A trajectory to "kiss" Europa's orbit would take a significant amount of radiation on the way out, versus a lot less on the speedy path in. Europa might even be, unluckily, at about the worst-case-scenario distance for radiation exposure on the post-aerobraking trajectory.

You'd definitely hope to get two-for-one value out of the radiation and entry shields. I don't know about the engineering constraints there, but if you could have a heavy metal providing heat shielding as well as protection against charged particles, that would leave a lot more mass for payload.
Go to the top of the page
 
+Quote Post
Guest_Zvezdichko_*
post Feb 9 2007, 06:04 PM
Post #3





Guests






Images attached. I'm not good at image design, but you should understand the basic concept of such lander...
Attached thumbnail(s)
Attached Image
Attached Image
Attached Image
 
Go to the top of the page
 
+Quote Post
tty
post Feb 9 2007, 08:09 PM
Post #4


Member
***

Group: Members
Posts: 683
Joined: 20-April 05
From: Sweden
Member No.: 273



That shield looks a lot like the massive copper heat-shield used by early Atlas missiles before ablative shields were developed. Is that a coincidence?
Go to the top of the page
 
+Quote Post
Guest_Zvezdichko_*
post Feb 9 2007, 08:23 PM
Post #5





Guests






Yes, that's a coincidence. I'm not familiar with these early Atlas missiles.
I've made the heat shield big just because the spacecraft needs best protection.
Go to the top of the page
 
+Quote Post
nprev
post Feb 9 2007, 11:51 PM
Post #6


Senior Member
****

Group: Moderator
Posts: 6960
Joined: 8-December 05
From: Los Angeles
Member No.: 602



Wouldn't avoiding the rings be a significant concern? Io & Europa are in equatorial orbits, same as the ring plane...seems like you'd have to still invest in considerable delta-V to make this work, given that the aerobraking pass would almost certainly have to be out-of-plane.

In fact, it seems as if it couldn't be done in just one orbit given this constraint. Translational maneuvers are most effectively performed during periapsis, and again this would have to thread the needle with respect to the ring plane...and, of course, your total radiation exposure goes way upwith every pass.

Sorry, Z, but IMHO there seem to be too many risks here. Interesting idea, though; my compliments! smile.gif Now. aerobraking mght work REALLY well for gas giant polar orbiters...


--------------------
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
djellison
post Feb 10 2007, 12:23 AM
Post #7


Administrator
****

Group: Chairman
Posts: 13712
Joined: 8-February 04
Member No.: 1



Well - rings are thin - very thin - so it would only take a minor orbital inclination from equatorial to avoid them - comparatively little Delta V - and nothing that couldn't be squeezed from flybys if necessary.

Doug
Go to the top of the page
 
+Quote Post
nprev
post Feb 10 2007, 01:32 AM
Post #8


Senior Member
****

Group: Moderator
Posts: 6960
Joined: 8-December 05
From: Los Angeles
Member No.: 602



Mmm...still scares me. Guess the real key would be to figure out exactly how "wide" (in terms of the vertical dimension) the ring danger zone really is. Seems like there still might be a significant risk of encountering material immediately above & below the plane if the rings are even a little bit dynamic (from collisions, meteoroid intrusions into the ring, etc.) Also, how much material is in the "LJO" zone near the desired near-equatorial aerobraking area? IIRC, Jupiter's ring extends inward nearly to the atmosphere... unsure.gif

Then again, maybe a grazing encounter with the rings would be a good thing. Presumably they act to dampen the local radiation levels at least a little...might improve mission assurance.


--------------------
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
mchan
post Feb 10 2007, 03:17 AM
Post #9


Member
***

Group: Members
Posts: 593
Joined: 26-August 05
Member No.: 476



The illustrations I recall of outer planets aerocapture probes have a streamlined shell shaped like the fuselage of a subsonic aircraft. The shell was asymetrically shaped as if the air resistance and corresponding deceleration could be controlled by rolling the shell on the flight tranjectory. This was in some OPAG powerpoint, but I could not find it again on the website.

The blunt aeroshell shown in this thread may caused too high of deceleration. Good for entry probes into Jupiter, but perhaps not for slowing down into orbit.
Go to the top of the page
 
+Quote Post
J.J.
post Feb 10 2007, 03:22 AM
Post #10


Junior Member
**

Group: Members
Posts: 84
Joined: 22-March 06
Member No.: 722



In my op, the biggest danger to any aerocapture mission is the uncertainty of the upper-atmospheric structure and density of the target planet. I imagine that the danger is proportional to the profile data gained from previous missions; perhaps at Jupiter and Satury it would be easy, but nearly a crap shoot at Uranus or Neptune.


--------------------
Mayor: Er, Master Betty, what is the Evil Council's plan?

Master Betty: Nyah. Haha. It is EVIL, it is so EVIL. It is a bad, bad plan, which will hurt many... people... who are good. I think it's great that it's so bad.

-Kung Pow: Enter the Fist
Go to the top of the page
 
+Quote Post
mchan
post Feb 10 2007, 03:57 AM
Post #11


Member
***

Group: Members
Posts: 593
Joined: 26-August 05
Member No.: 476



Given uncertainty, having some control over the deceleration by varying the aspect / angle of attack of the aeroshell would appear to be a design requirement for aerocapture.
Go to the top of the page
 
+Quote Post
tasp
post Feb 10 2007, 06:34 AM
Post #12


Member
***

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



Had the Galileo orbiter 'bobbled' the trajectory for the atmospheric probe, it might have 'skidded' off the atmosphere and into a probably not very long lived orbit about Jupiter.

So aerocapture is certainly possible, and was probably something worried about extensively as something to avoid during the Galileo mission.
Go to the top of the page
 
+Quote Post
mimile
post Feb 11 2007, 10:18 AM
Post #13


Newbie
*

Group: Members
Posts: 3
Joined: 24-December 06
Member No.: 1511



I don't think the proposed method (a spacecraft aerobraking in Jupiter's top atmosphere then going back to Europa, and arriving with a velocity parallel to Europa's) will work in practice.

I find that the the relative velocity spacecraft wrt Europa would be 4.3 km/s in the best case. This is too much for usual chemical propulsion to slow it down to land.

All studies performed with numerous flybys of Ganymede and/or Callisto to bring the spacecraft to Europa result in a relative velocity that is manageable.

Good ideaa, though !
Go to the top of the page
 
+Quote Post
tasp
post Feb 11 2007, 03:07 PM
Post #14


Member
***

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



I am thinking an analog of the Messenger mission to Mercury trajectory is quite feasible in the Jupiter system. The mass ratio of Jupiter to Io, Europa, etc. is more favorable for larger manuvers than the mass ratio of the sun to Mercury, Venus, etc.

Also, realize that a reverse trajectory from Mercury to either Venus or Earth is possible, and therefore an analog of this trajectory will be possible in the Jupiter system. A craft can approach Europa from 'below' {after Io flyby(s)}, or from 'above' {after Ganymede and/or Callisto flyby(s)}.

And as we see with Mercury, the target objects gravity can also provide manuvering capability. So flyby's of Europa (coupled with trajectory 'tweaks') can further reduce fuel requirements to orbit Europa.

One major challenge to flying this mssion is the long time spent directly in the most intense part of Jupiter's radiation, however.

If the mass ratio of Jupiter to it's satellites is sufficiently more favorable than the sun/inner planet ratio, perhaps an analog to the Messenger trajectory can be found that has an appreciable tilt the the Jupiter equatorial plane. Maybe, just maybe, the synchronized orbits of Io, Europa, and Ganymede make this easier.

Inclined trajectories cross the equatorial plane twice per orbit, having Europa being 180 degrees around from Io and Ganymede might facilitate gravitational trajectory manuvers often enough for this trick to work.
Go to the top of the page
 
+Quote Post
mchan
post Feb 12 2007, 07:46 AM
Post #15


Member
***

Group: Members
Posts: 593
Joined: 26-August 05
Member No.: 476



If by analog to Messenger trajectory, you are referring to using relatively small deep space engine burns to trim the orbit back into 3:2, 4:3, 6:5, etc. resonance with the target for a subsequent grevity assist, then the previous JPL Europa orbiter mission design made use of this technique. The final orbit around Jupiter prior to Europa orbit insertion had a low delta-V between the spacecraft and Europa orbits at the encounter. IIRC, the actual burn requirement was further reduced by using the interaction for Jupiter gravity to drop the spacecraft into Europa orbit.
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 August 2014 - 06:34 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.