henry (04/26/83)
Approximately one hour ago (1700 EDT 25 April 1983), Pioneer 10's distance from the sun exceeded that of Pluto (which at the moment is closer to the sun than Neptune). On 13 June 1983, Pioneer 10 will "pass" Neptune as well, thereby becoming the first man-made object to leave the solar system.
silver (04/28/83)
Sorry to disagree with you, but crossing the orbit of any planet does not make a spacecraft interstellar. I argue that that event occurred precisely at the moment the engines (or the planet it was passing -- did it use gravity assist?) gave Pioneer 10 escape velocity.
preece (04/29/83)
#R:utzoo:-292900:uicsl:11100009:000:350 uicsl!preece Apr 28 09:08:00 1983 Isn't it a little parochial to use the term solar system to refer only to the portion of space swept by the known planets? Even if we assume that there is no unknown planet (and this assumption is doubted by perfectly respectable astronomers), there is a much larger area of space occupied by objects that are still controlled by the Sun's gravity.
CSvax:Pucc-H:Physics:crl@pur-ee.UUCP (05/02/83)
Relay-Version:version B 2.10 delta 4/26/83; site burl.UUCP Path:burl!spanky!ihnp4!ixn5c!inuxc!pur-ee!CSvax:Pucc-H:Physics:crl Message-ID:<751@pur-phy.UUCP> Date:Mon, 2-May-83 13:05:12 EDT #R:utzoo:-292900:pur-phy:11400001:000:343 pur-phy!crl May 2 09:39:00 1983 I disagree with the statement that a craft is interstellar when it reaches the sun's escape velocity. It could always brake to go into some planetary orbit couldn't it? Analogously, would we consider the APOLLO missions interplanetary just because they exceeded earth's escape velocity? Charles LaBrec pur-ee!Physics:crl purdue!Physics:crl
karn@eagle.UUCP (05/03/83)
Relay-Version:version B 2.10 delta 4/26/83; site burl.UUCP Path:burl!spanky!hocda!houxz!houxm!mhuxa!mhuxj!mhuxt!eagle!karn Message-ID:<926@eagle.UUCP> Date:Mon, 2-May-83 22:04:50 EDT Yes, a spacecraft is indeed interstellar when it exceeds the sun's escape velocity, unless of course it impacts some object standing in the way. Braking into orbit around a planet takes a considerable amount of energy. The best look at a planet that can be achieved without braking in a two-body situation (which is a very good approximation) is a hyperbolic flyby. The velocity required to reach the moon is not quite earth escape velocity; it is approximately the velocity required to inject the spacecraft into an elliptical orbit with the apogee at the moon's orbit and perigee at the parking orbit altitude. In fact, this is how lunar missions were planned. A simple two-body approximation was first made (ignoring the moon) followed by computationally intensive numerical integrations in which the various orbital parameters were iterated until the "best" results for lunar orbit insertion were obtained. There are still no simple analytic ways to optimize arbitrary multi-body trajectory problems. Phil