September 25, 2017

02.06.10: Dawn-A New Way to Explore the Solar System.


NSTAR electrostatic ion thruster under test. (Credit: NASA/JPL/Dawn).

NSTAR electrostatic ion thruster under test. (Credit: NASA/JPL/Dawn).


   An asteroid-bound spacecraft is also blazing a trail for technologies of the future. Dawn, NASA’s asteroid rendezvous mission blasted off from Cape Canaveral September 27th, 2007 enroute to explore the asteroids Ceres and Vesta starting next year. But unlike previous solar system missions, Dawn is able to do something that most interplanetary spacecraft can’t; change trajectories. Older traditional chemical rockets rely on their initial imparted thrust to get them on their way, but once that’s applied, the course is set. Beyond gravitational sling-shotting, little can be done to adjust their overall orbital paths, and you can’t park in orbit and visit interesting bodies, a major drawback. Dawn instead utilizes ion thrust engines. These provide a low thrust over a long period of time, rather than a chemical rockets’ high thrust in a short period of time. Although it requires Dawn a lengthy period to build up speed, its Xenon-solar powered drives ultimately win the race where specific impulse is concerned. This also enables it to carry a relatively light load of propellant. In fact, Dawn carries enough Xenon propellant for over 5 years of use. First proposed by none other than American rocket pioneer Robert Goddard in 1906, Ion based propulsion was first tested in 1959 at NASA, and utilized in the first  spacecraft aboard SERT-1 in 1964, and then more famously aboard Deep Space 1 in 1998. Many science fiction fans will remember the reference to ion drives in the original Star Trek episode “Spock’s Brain,” and the lineage can no doubt be traced further back in pulp Sci-Fi literature. Other spacecraft, such as the heroic Hayabusa returning to Earth next week and the proposed LISA Pathfinder, also utilize ion technology. Ion drive is well suited for asteroid exploration due to their low gravity fields, but in time missions bound for the major planets and moons could sport ion drives, as well. What Dawn will find as it nears the two asteroids is waiting to be seen; Vesta is a rocky terrestrial-type asteroid which may resemble early proto-solar material that formed rocky worlds like the Earth, and Ceres may even harbor a Europa-style environment, complete with ice enshrouded oceans! Dawn is scheduled to orbit Vesta for a year starting in July, 2011, and arrive at Ceres in February 2015. Perhaps, history will record that it was the ion-drive that truly opened up space exploration, and was ultimately how the solar system was won!

Apollo 11 40 Years Later: Did We Really go to the Moon?



As the 40th anniversary of the historic Apollo 11 Moon landing rolls around this month, its time to address the inevitable. Every so often at a star party, someone asks me if you can see the flag(s) we left on the Moon. When I explain that even the largest pieces of hardware, the base of the lunar landers, were only a scant seven meters across, far below the resolution power of my 8″ reflector, someone inevitably pipes up in the dark; “because we never did go there, that’s really why!”

Of course, I already know that no amount of reasoning will dissuade some people; the outlook is “the government hides everything,” and that tends to be the ultimate answer for any conspiracy. [Read more...]