Asteroid Grand Tour |
Asteroid Grand Tour |
Apr 7 2007, 01:31 AM
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#1
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Merciless Robot Group: Admin Posts: 8784 Joined: 8-December 05 From: Los Angeles Member No.: 602 |
This article from JPL describes recent efforts to derive a main belt multi-asteroid mission trajectory...any of you orbitsmiths out there have some early thoughts/observations?
-------------------- 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.
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Apr 7 2007, 05:49 PM
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#2
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Administrator Group: Admin Posts: 5172 Joined: 4-August 05 From: Pasadena, CA, USA, Earth Member No.: 454 |
Last year's was a very different challenge. From the Problem Description (PDF):
QUOTE The main objective of the optimisation is to maximise the change in the semi-major axis of the asteroid 2001 TW229 subsequent to the impact of an electric propelled spacecraft. I'm more interested in this year's results...I'd love to see a multi-asteroid tour. Dawn will get two, but that's in part because it's aiming for two very specific ones, and is going into orbit at both. Another mission that was less constrained could surely survey more in shorter time.1-The target Consider the asteroid 2001 TW229 and its osculating orbital elements in the J2000.0 heliocentric ecliptic reference frame: a (semi-major axis, AU): 2.5897261 e (eccentricity): 0.2734625 i (inclination, deg.): 6.40734 ω (argument of pericenter, deg.): 264.78691 Ω (Right Ascension of the Ascending Node, deg.): 128.34711 M (mean anomaly at epoch 53600 MJD, deg.): 320.47955 2-The spacecraft Consider a nuclear electric propelled spacecraft with a wet mass of 1500 kg (dry mass can be considered to be zero) and equipped with a thruster with the following capabilities: specific impulse Isp=2500 sec., maximum thrust level T=0.04 N. 3-The mission The spacecraft has to be transferred from Earth to the asteroid 2001 TW229 with a launch in [3653-10958] MJD2000 (Modified Julian Date 2000), corresponding to years 2010 to 2030. The maximum time of flight is 30 years. At arrival the quantity {equation: J = mf |U-rel dot v-ast|} has to be maximised, where mf is the final mass of the spacecraft, U-rel is the velocity of the spacecraft relative to the asteroid at arrival and v-ast is the heliocentric velocity of the asteroid. The launcher available for the mission is able to provide a 2.5 km/sec escape velocity to the spacecraft with no constraint on the escape asymptote direction. Consider also a constraint on the minimum allowed heliocentric distance of 0.2 AU. 4-The dynamical models Consider only the Sun gravity as an external force acting on the spacecraft. Planets may be used to perform swing-bys, in this case the effect should be modelled as an instantaneous direction change on the spacecraft velocity relative to the planet, subject to a constraint on the angle magnitude (a minimum pericenter radius has to be considered, see table below for details). The planet ephemerides used should have an accuracy equivalent to that of JPL DE405 ephemerides (http://ssd.jpl.nasa.gov/horizons.html). Use the numerical values given below and assume the astronomical unit equal to AU=1.4959787066e+008 km, and the Earth standard gravitational acceleration to g0=9.80665 m/s2. CODE Mercury Venus Earth Mars Jupiter Saturn Sun Gravitational Constant, km^3/sec^2 22321 324860 398601.19 42828.3 126700000 37900000 1.32712428 e+011 Minimum pericenter radius allowed during fly-by, km 2740 6351 6678 3689 600000 70000 N/A --Emily -------------------- My website - My Patreon - @elakdawalla on Twitter - Please support unmannedspaceflight.com by donating here.
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Apr 7 2007, 11:39 PM
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#3
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Senior Member Group: Members Posts: 2530 Joined: 20-April 05 Member No.: 321 |
I'll echo my concept of a retrograde solar orbit for a truly grand tour of the asteroids. A craft would use a Jupiter gravity assist to enter a retrograde orbit with perihelion 2.6 AU and aphelion 5.2 AU. When it first returned to the asteroid belt, it would fire its engines to enter a roughly circular orbit barreling in reverse right down the middle of the asteroid belt. It would be trivial to set a course intersecting any two asteroids named as primary goals. Other encounters would happen automatically, with the craft passing the radial position of some asteroid or other every few hours. Of course, in most cases, the distance would be quite great, but every few months should bring a somewhat close encounter even if only by chance. With a few more manuevers and a little planning, it should be easy to set up a large number of encounters, albeit fast ones. This would result in a lot of encounters that would map only half of an asteroid (with the craft flying by too fast to see the other half rotate into daylight), but the numbers should roll up rather impressively. I would think a dozen encounters would be a conservative estimate.
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Jan 7 2017, 02:52 PM
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#4
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Member Group: Members Posts: 684 Joined: 24-July 15 Member No.: 7619 |
I'll echo my concept of a retrograde solar orbit for a truly grand tour of the asteroids. A craft would use a Jupiter gravity assist to enter a retrograde orbit with perihelion 2.6 AU and aphelion 5.2 AU. When it first returned to the asteroid belt, it would fire its engines to enter a roughly circular orbit barreling in reverse right down the middle of the asteroid belt. Hmm, circular orbit at 2.5 AU down the 3:1 gap, should have roughly 2,200 asteroids within .1 au. Figure 30 months orbit at that distance, but retrograde should pass everything in 15 months. That's an average of 2.4 close approaches per day. Wonder if it's possible to program such complex targeting sequences... |
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