Space mission design is the artistic technology of charting the navigational route of a spacecraft. In space, there is no air resistance or obstacles, but instead, spacecrafts are affected by the gravitational fields of the sun and planets. The beautiful arcs of the routes, which strictly follow the simple equations of motion in space, are a work of art. Designing such routes to meet mission objectives is the preoccupation of Yuji Takubo, a student at Georgia Tech and an intern at NASA’s Jet Propulsion Laboratory (JPL). He explained to me what it is all about.
Space mission design is an engineering technology that applies theoretical physics. On the one hand, there is astrodynamics, and on the other hand, space mission design. Astrodynamics deals qualitatively with the interaction of several “points” generating gravitational fields and the movement of each point (called multi-body problem). Space mission design, on the other hand, quantitatively designs the route of a certain spacecraft to fly, given the gravitational fields of the Moon, Earth, other planets, etc. Therefore, the application of astrodynamics to real space is space mission design.
One attraction of space mission design is its elegance. This is because spacecraft routes are complex but beautifully curved with little human intervention. Once launched, spacecrafts are difficult to control. Therefore, it is essential to let the spacecraft fly without control as much as possible, letting the gravitational field take care of it, “like letting it flow on a river,” Yuji says. The route is designed in the same spirit as dominoes; once the first domino is toppled, the rest fall in sequence, and the goal is reached.
However, this does not mean that you can draw any routes as long as you reach the goal. One of Yuji’s jobs is to “optimise” the route by maximising or minimising certain factors. For example, cost reduction is a priority, so engineers will optimise routes to minimise fuel consumption. For example, it would be unwise to take 100 days to the Moon with astronauts on board because it would be too uncomfortable to be in a small cockpit with limited infrastructure for such a long period, even if the amount of fuel consumed would be minimal. But if you are delivering regularly needed supplies with limited astronauts on board, you don’t need to be in such a hurry, and a route that minimises fuel consumption would be better. So the design of the route is to some extent constrained by the objectives of the mission.
It is basically the same as in the logistics industry, where they use different travel methods and routes depending on the goods being carried, the purpose, and the destination.
What is fundamentally different from the logistics industry, however, is the peculiarity of the environment. If you choose the wrong road while driving a truck, you can come right back. But a spaceship flies far from Earth, often unmanned, for an extremely long period of time. Even if you send a command, it takes a long time for the spacecraft to receive it. So once it is launched, it is very difficult to control. That is why meticulous route design is essential for the success of a space mission. If it does not reach its destination, it cannot fulfil its original purpose. Thus, the engineers work hard to send the spacecraft to its destination.
New technologies are also being developed to navigate such a challenging space environment in new ways. It is becoming possible to equip the spacecraft with computational intelligence and to control its position by itself in space. Yuji finds it exciting to navigate a spacecraft with the combination of “onboard” autonomous decision-making design and the “pre-launch” route design.
Yuji is excited to “contribute to the accumulation of people’s knowledge by meeting the demand from science.” Each spacecraft has its own purpose: NASA’s JPL has a project to fly a spacecraft to Enceladus, one of Saturn’s moons. There, scientists want to find out about potential living organisms and what kind of environment they live in. To do this, they need to carry out surveys, such as soil sampling, but the scientists don’t know how to fly a survey kit that far, and the engineers are therefore working out how to solve this problem. They are fulfilling scientists’ dreams of knowing more about space and other planets through the drawing of maps.
Technology is not limited to physical machines; it is about using abstract scientific theories with purpose. Yuji and other engineers use astrodynamics to design routes for the purposes of their missions — the intellectual activity itself is technology as an enabler of a purpose.
If you are interested in learning more about space missions, feel free to check out this video “Rosetta’s twelve-year journey in space” created by the European Space Agency in 2013.