Mercury Lander

Planet Mercury is the closest planet to Earth more frequently than any other planet. However, reaching it takes a long time because of high level of acceleration due to Sun’s gravity. A Mercury missions spends almost 70% or more time trying to decelerate using gravity assists. I would like to propose a propulsion-based deceleration for a Mercury mission to shorten the journey.

This propulsion is only advantageous for missions close to the Sun. The idea is to use Sun’s gravity and heat to counteract its gravity. I will explain my idea on a cassette spaceship module. This idea would work even better on a cylindrical spaceship.

The idea is simple; pressure a liquid, in my case mercury by coincidence, and eject it towards the Sun to decelerate the spaceship. The nose of the spaceship would have dry ice, behind that a piston and behind that liquid mercury. In the middle of this setup, there would be a thin ejector pipe. As the spaceship accelerates, the inertia would push the piston towards the rear of the rocket. In the meanwhile, dry ice would sublimate and turn into gas due to immense heat from the Sun. These two additive forces would push the mercury inside the thin pipe to be ejected towards the direction of movement. Hence, the rocket would be decelerated.

In classical chemical propulsion-based rockets, the accelerated material gets its momentum from the heat generated by the chemical reaction. However, in my design, the Sun is accelerates the ejected material. Therefore, heavier the material, higher the thrust would be. That’s why I opted for mercury. Its liquid form does not allow compression. As a result, all the pressure applied to it goes to accelerating the ejected mercury. Expanding carbon dioxide from dry ice fills up the void behind the piston and pushes it besides the Sun's gravity. In that case, the Sun’s heat is doing the work.

Compared to a methane and LOX rocket, my design produces the same amount of total thrust for half the amount of weight. The high density of mercury also reduces the volume of the propulsion stage considerably.

In the modular deep space mission rocket, the module I proposed now would be used to decelerate the spaceship so that it can directly land on Mercury without spending years for gravity assist deceleration.