DFD at the IEPC

Explosions. Orbits. Stuff hurtling through space at high speed. At the George Washington University campus last week, eyes young and old were trained on the screen, witnessing an amazing story of what can happen in space.

And no, it was not “Gravity”. Nothing against Ms. Bullock or Mr. Clooney, but the 33rd International Electric Propulsion Conference was the place to be last week. The IEPC showcased some fascinating new developments in electric propulsion, including some very promising work on plasma and fusion engines. MSNW gave a great overview of their Fusion Driven Rocket, Ad Astra showed off impressive experimental results of their VASIMR engine, and the University of Surrey presented a novel quad confinement thruster, to name a few.

We were happy to present our paper on the Direct Fusion Drive Rocket for Asteroid Deflection.

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Direct Fusion Drive to Mars – A FISO Talk

The Future In-Space Operations (FISO) working group invited us to give a talk in their weekly seminar track. On Wednesday, July 24, 2013, we gave a presentation entitled “Direct Fusion Drive for Fast Mars Missions with the Orion Spacecraft”. You can find the slides we presented in their online archive here.

We first discussed the need to get to Mars and back home fast (see our recent blog post on the risks of extended durations in space). We then presented some preliminary studies on the double rendezvous problem of Earth -to- Mars -to- Earth, and introduced the Direct Fusion Drive (DFD) as a future propulsion technology that can make this mission happen.

Dozens of people dialed in from around the country. Dr. Dan Lester (U Texas) and Dr. Harley Thronson (NASA Goddard) gave us a warm introduction, and there were a number of insightful questions throughout the talk that sparked interesting dialog. We were also joined by colleagues at MSNW who are developing another form of fusion propulsion, called the “The Fusion Driven Rocket“.

It was an honor to be part of the FISO working group. The questions and feedback we received from this group have been extremely valuable, and it is another sign of the growing interest in fusion propulsion!


Move it or lose it!

Space is silent. No air, no sound. This must have seemed strange on February 10, 2009, when the satellites “Kosmos-2251” and “Iridium 33” collided, shattering the spacecraft into more than 2,000 pieces of debris. Now, each of these pieces presents a new risk of collision to our satellites in low Earth orbit.

An example collision avoidance scenario between two close-orbiting satellites.

An example collision avoidance scenario between two close-orbiting satellites.

The potential to collide with other satellites or debris is a real and growing concern. As a result, collision detection and avoidance are becoming a critical aspect of satellite operations.

We have worked on new collision avoidance algorithms and strategies for several different projects, including the Prisma formation flying mission which was launched in 2010.

Some of our work in this area was just published in the Journal of Aerospace Information Systems. The paper is “Avoidance Maneuver Planning Incorporating Station-Keeping Constraints and Automatic Relaxation”. You can find it here: http://arc.aiaa.org/toc/jais/10/6

The paper discusses different ways to model the time-varying avoidance region that represents the predicted path of another satellite, and methods for computing minimum-fuel maneuvers that satisfy both the avoidance constraints and station-keeping constraints for the mission. The details may be complex, but the message is simple: “Move it or lose it!”

Is that a spaceship in your pocket?

I remember the day my dad brought home our very first VCR. It was a glorious invention. No longer were our family outings constrained by the TV Guide. This nifty VCR would magically record our favorite shows and allow us to play them back whenever we wanted. It wasn’t long before we had a cabinet full of unlabeled tapes — most of which were never watched again, except while searching for something we accidentally recorded over. But still, it was cool.

That first day, my dad and I watched “The Empire Strikes Back”. Twice! Being just five years old, this was my first “real” movie. I remember in the opening scenes, the huge imperial star destroyer floating ominously across the screen. It seemed to go on forever. Okay, so this is a spacecraft.

Fast forward 32 years. Everything seems to have gotten… smaller.

We can now manage our DVR, record our own digital movies, tweet, text and call from that little smartphone in our pocket. And those huge spaceships from 1980’s fiction? They are now about the size of that first VCR.

We’ve recently designed a 6U CubeSat capable of escaping Earth orbit, rendezvousing with an asteroid, and returning to Earth. Its called “Asteroid Prospector”. It’s shape is 12 x 24 x 36 cm, which is about 5 x 10 x 15 inches, and it weighs about 40 lbs. In other words: its a 1981 VCR. But it goes a lot faster.

Earth departure spiral for the Asteroid Prospector

Earth departure spiral for the Asteroid Prospector

The Asteroid Prospector is propelled through space using a Busek Bit-3 ion thruster. It uses electric power to accelerate ions out the nozzle at high speed, pushing the spacecraft in the opposite direction of the ion stream. This gives us a small thrust of 1.9 mN, but it can operate for nearly 3 years on just 5 kg of propellant! We are presenting the spacecraft design, mission analysis and example asteroid rendezvous simulations at the upcoming SmallSat conference.

Fast forward another 32 years. Is that a spaceship in your pocket?