Problem A Solar Sailing to Mars

Light exerts a pressure equal to twice its energy density when reflected from a surface.  Therefore, a large, lightweight reflective surface known as a solar sail allows radiation from the sun to propel a spacecraft.    Assume that the sail is made of material of mass 7 g/m²; a rocket will launch a total mass of 2,000 kg (sail plus payload) to escape velocity from Earth.  Determine the size of the sail and a flight plan for the solar sail spacecraft from Earth to Mars.  Assume that the Earth and Mars are at their closest approach at the time of launch and that the spacecraft and Mars must have a relative velocity of no more than 9 km/s for safe landing.  Optimize the flight plan to maximize the payload and reduce transit time.

Problem B Ion Thrusters

Ion thrusters can be an effective means for propelling space probes through our solar system.  Gridded electrostatic ion thrusters begin by ionizing their propellant, accelerating the positively charged ions using a potential difference between two or more grids, and then neutralizing the exhaust by firing a beam of electrons into it.  A research team is working on a prototype Xenon ion thruster, 35 cm in diameter, with a specific impulse of 5,100 seconds and a thrust of 350 millinewtons.  However they find that ions exit the final grid at a wide range of angles.  A member of the team proposes that you could generate a magnetic field that would affect the trajectories of ions out of the final grid, before the ions are neutralized, to direct their velocities into a more uniform exit direction.  Evaluate this proposal.  Would it be practical to generate such a magnetic field, and if so, how?

The following announcement of results was made on Tuesday, January 17, 2018:

We are very pleased to announce the results of the eighth annual University Physics Competition.  The University Physics Competition is an international contest for undergraduate students, who worked in teams of up to three students at their home colleges and universities all over the world, and spent 48 hours during the weekend of November 10, 11, & 12, 2017, analyzing an applied scenario using the principles of physics, and writing a formal paper describing their work.

In this year’s competition 265 teams submitted papers for judging.  193 teams selected “Problem A – Solar Sailing to Mars” and 72 teams selected “Problem B – Ion Thrusters.” 

For Problem A, the Gold Medal Winning Teams were:

Team 670:  Wojciech Zwoliński, Marcin Kalinowski, & Jerzy Szuniewicz

Institution: Faculty of Physics at the University of Warsaw

Faculty Sponsor:  Wojciech Dominik

Team 670's 2017 Problem A Gold Medal Winning Paper

Team 699:  Liu Pengtao, Long Kehan, & Li Ruojing

Institution: National University of Defense Technology

Faculty Sponsor:  Gang Peng

Team 699's 2017 Problem A Gold Medal Winning Paper

Institution: Universitat Autònoma de Barcelona

Faculty Sponsor:  Ramon Muñoz Tapia

Team 744's 2017 Problem A Gold Medal Winning Paper

For problem B, the Gold Medal Winning Team was:

Team 609:  Sohair Abdullah, Jackson Schrott, & Nicholas Crews

Institution:  Colorado College

Faculty Sponsor:  Stephanie DiCenzo

Team 609's 2017 Problem B Gold Medal Winning Paper

Of the 265 papers submitted in the 2017 University Physics Competition, 4 teams (1.5%) were ranked as Gold Medal Winners, 48 teams (18%) were ranked as Silver Medal Winners, 71 teams (27%) were ranked as Bronze Medal Winners, and 142 teams (54%) were ranked as Accomplished Competitors.

We extend our sincerest congratulations to each of the competing teams for their excellent work and their enthusiasm for physics!

Kelly S. Cline

Carroll College; Helena, MT

Director of the University Physics Competition

director@uphysicsc.com

www.uphysicsc.com