Space Reimagined

Over the years, our knowledge of the universe has expanded and the transition from Sputnik 1 to Falcon 9 is a testament to this expansion. In recent times, the globe has adopted a ‘green’ way of living and as a team, we embarked on a journey to catch sight of the future of ‘green’ space and this article is where we arrived.

Current Latest Technology

One of the most remarkable things about deep space exploration is the sheer number of resources required to make it feasible. Be it in the form of fuels for take-off, aluminium and titanium alloys for

the body of the spaceship or even the tens of millions of dollars needed to fund the Spacecraft

Assembly Facilities, space travel is costly.

This is where the reusable rocket launchers come into play. Until just a couple years ago, we did not have the technology to economically implement space crafts that could be used repeatedly. While the Space Shuttle was partially reusable, it cost a whopping $450 million per launch on average.

One of the first people to identify the lack of reusability of equipment was Elon Musk and in 2017 he launched SpaceX Falcon 9, the first of which is a restartable ignition system for the first-stage

booster. Implementing renewable and reusable features in rockets will significantly reduce costs,

crossing off one of the main doubts about the funding of deep space exploration.

Alternative Renewable Fuels

‘Is it possible to explore space in an environmentally friendly way?’ 

This question was the catalyst that led us to ASCENT (AF-M315E) and the Hall effect engines.

ASCENT is a hydroxyl ammonium nitrate fuel with a unique oxidizer blend that makes it a dream

fuel for future use. It is more dense and less toxic compared to hydrazine, only emits non-toxic

gases during combustion and can be used as a monopropellant. It enters a glass transition phase in cold environments and does not expand when solid. The Hall effect engines are also equally unique. The engines use ions accelerated in an electric field to use them as ionized propellants so that the engines can accelerate to speeds of 80 km/s. The Hall thrusters have been used in space since 1971 and their 100% success rate has encouraged its use commercially in LEO and GEO satellites.

We have incorporated the use of both these fuels in our one stage propulsion spacecraft using serial staging to build a more eco-friendly and convenient way to explore space.

Renewable Propulsion Systems

Hall effect and Ion thrusters follow similar basic principles of electrical propulsion systems and are

based on xenon propellants making them ideal to be used from the low-earth orbit to the geostationary orbit.

Both electrical propulsion technologies were independently focused on by the US and USSR in the

1960s when they displayed their outstanding efficiency and the potential to be used independent

from fuels, relying on only electricity and magnetic fields to accelerate xenon atoms.

Hall thrusters consist of an annular solenoid, plasma chamber, cathode, and a xenon injector anode. Xenon atoms were chosen due to their high atomic weight and low ionization potential and

their non-radioactive and inert characteristics. Its high atomic weight allows for a denser packing

even at a low pressure.

Electrons are first emitted from the cathode and move to the anode in the electric field strength and

are later captured as the magnetic field moves in the plasma chamber. Then xenon gas is injected

from the anode into the plasma chamber where it is ionized due to the electrons present. Once this

occurs the positive xenon ions will provide thrust as they accelerate axially and fly out in the electric

field however, due to their heavy mass they are not affected by the magnetic field.

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What enables hall thrusters to be a more efficient choice among other alternatives in comparison to

ion thrusters is its ability to inject both the electrons and xenon atoms within a radial magnetic field

present in the plasma chamber also helps in neutralizing space charge.

On the other hand, ion thrusters have a more gridded design and therefore, there is no quasi-neutral plasma, so the Child-Langmuir charge (space charge) saturated current causes a limitation on the thrust density. As Hall effect thrusters have this quasi-neutral plasma, they can provide much smaller thrusters in comparison to ion gridded thrusters as well as depend on a wide variety of propellants like oxygen, argon, bismuth, iodine, magnesium, or zinc other than the conventional xenon and krypton atoms. The focus remains on using any element that can be easily ionized that can be injected from the cathode.

The power is generated from a sub-system which depends on a solar array and can also be obtained from photovoltaic cells once upgraded by being able to utilize a greater fraction of electrical energy to produce thrust while focusing on minimizing this electrical energy being lost as waste heat radiated to space.

Hall effect thrusters usually have low operational life due to the plasma chamber being made of ceramic which would get eroded therefore, damaging the magnetic system. This problem can be

easily overcome by shielding the magnetic system to eliminate the possibility of xenon plasma

produced from damaging it. This is done by substituting the discharge channel with a wall

replacement mechanism to extend the lifetime by five times.

Discharge efficiency is also improved as energy loss to the plasma chamber is reduced. Furthermore, this innovation comes with an actuator that can either be mechanical or programmable to extend the sleeve and the discharge chamber along the centreline axis. After the development, the Hall effect thrusters can supply an exit velocity of 65,000 miles per hour with a lifetime of around 50,000 hours.

Economical and Financial Aspects

As expected, the process of designing, building and subsequently launching a rocket can be an

extremely expensive process but despite the costs we still choose to explore the universe. Why?

Because of the countless economic benefits of space exploration, of course!

Through space exploration there has been an exponential growth in technological advancements and the growth of brand-new industries and scientific fields. The average cost of the process is $90 million to $300 million, however, with various modern innovations the cost of the process is steadily

decreasing. By using reusable rockets, the cost of launching a rocket could potentially be significantly decreased, which could expand the space exploration industry and make it more accessible.

The Falcon 9 is an excellent example of the financial prospects of reusable rockets, the initial launch

of the Falcon 9 cost approximately $62 million dollars, while it only costs $50 million when reused. This price could be dropped further with our innovative rocket design that is both reusable and uses a one stage propulsion.

While the reusability of the rocket might decrease the costs of its use, the use of energy sources that

are environmentally friendly is costly and will increase the cost of the manufacturing and launching

the rocket. Keeping that in mind we chose energy sources that are not only environmentally friendly

but also efficient and durable to decrease the costs.

The cost of using environmentally friendly energy sources remains high but the countless benefits that

arise from their use are worth the price as these sources can lead to economic prosperity in the future. The use of green fuel does increase the cost of the launching and manufacturing of the rocket, but on the other hand, it decreases the costs of other processes such as the cost of the handling, transport, storage, and the disposal of the fuels. Moreover, we believe that with the current exponential growth in the technological industry the price of environmentally friendly energy sources will significantly decrease soon.

To conclude, renewable space exploration may be closer than we imagined. With the alternatives to fossil fuels on their way and the possibility of a single stage propulsion system in the works we now have a greater understanding of what lies ahead and can safely say we are almost there.

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Aaditi Rammohan, Catherine Joy, Lujain Elmallah and Gokulan Kumarananthan