The Fourth Stage

Since the beginning of space exploration, humanity could only send surface explorers to Mars with few exceptions. Main reason for that is the time it takes for a payload to reach the planets. We need to increase the payload’s average speed during its long voyage. In my planetary rocket design, I dedicated the fourth stage for that. This stage needs to generate high thrust like the previous stages.

An option can be to have a liquid methane engine to generate high thrust. For this task, a highly efficient but small engine can be developed. As a result, the thrust would be generated over a longer duration and the rocket would not be stressed by high g-forces.

Another option would be to use ion thrusters. However, a special engine needs to be developed to generate enough thrust for the heavy rocket. The gasses used in ion thrusters are quite expensive and supplying large volumes to satisfy the thrust requirement can be quite expensive. Additionally, ion thrusters require electricity for the thrust. While travelling away from the sun, not much electricity can be generated and protruding solar panels may not be reliable.

My proposal is a rocket stage filled with dry ice and Plutonium 238 heated nozzles. The idea is to convert small portions of dry ice into carbon dioxide and eject it from a tiny nozzle. The details are shown on the diagram. A Pu 238 tube with tiny holes on its sides would be used to heat the dry ice and pressurize it to generate thrust. The tube would be initially covered by an insulator low melting plastic that leaves no residue. This shield would prevent the dry ice from premature melting. The delay is the duration for the lower stages to complete their duties. Once the insulation melts away by the heat of the isotope, the rocket would start generating thrust. This is a much simpler and reliable design compared to the rest. Utilizing heat generated by radioactive decay gives the stage high ISP. The carbon dioxide gas would be exhausted from a tiny hole to accumulate higher pressure inside. This also increase the duration of the thrust generated.

The stage would be covered by a detachable heat shield. This shield would keep the dry ice cold during the atmospheric escape. Once the rocket is in LEO, the shield would be released to reduce weight. The released shield would than burn away in the atmosphere.

This simple stage can be cascaded to generate even more thrust.

Five Stages of a Planetary Rocket

The planetary space missions are the most complex and energy intense missions of all. By planetary missions I mean deploying a probe or explorer on the surface of a planet. Due to limitations of current rockets, only small probes and rovers could be send. With a purpose build rocket, we can explore our solar system better.

As a starting point, an economical rocket family can be developed. It would be configurable to suit missions. As a single rocket, it would be able to deploy LEO and geostationary satellites with its first stage recovered. Most probably a rocket with a maximum diameter of 5 meters would be enough for the task.

It’s not economical to recover stages beyond the first stage. As a result, the upper stages should be optimized for single use only. The objective of the second stage would be to put upper stages into low Earth orbit. LEO and geostationary missions would only have two stages.

In order to deploy heavy payload to the moon, at least three first stage rockets would be strapped together. The second stage would be a single rocket, so as the third stage.

Ideally, the first three stages of the rocket would utilize liquid methane engines with optimized nozzles. Utilizing the same engine in all three stages lower the costs and increase the reliability of the rocket while you can perfect a single engine compared to multiple ones.

The fourth stage would be used to accelerate the upper stages further to reduce the time to reach the planets. Ion thrusters can be an option. I also would like to propose a simple dry ice thruster powered by Pu 238 (details on my next article).

The fifth stage is a question mark. It would be used to safely descent the payload to the surface of the planet. It would be fired after many months of space travel. I don’t know if a liquid methane engine can be cold started in such a circumstance.

The Forgotten Stages of Rocketry

I have recently proposed a Mars Research Base. An adequate rocket is required to implement it. The rocket should have five stages. The first one can be a reusable heavy lift rocket. The second one would put the upper stages into LEO. The third one would free the upper stages from Earth’s gravity. The fourth one would guide the upper stages during the long journey to Mars. The fifth one which carries the payload would be used to descend the payload safely on Mars.

Almost every spaceflight company on Earth is working on their reusable first stage. Some even try to reuse the second stage as well. However, the upper stages get almost no attention. “The chain is only as strong as its weakest link”

Companies claim that they would conquer Mars with their two stage rockets. I give no chance to such designs. Even the government agencies are in the same mindset. The physics of rocketry has not changed since the Apollo program. An efficient rocket needs to get rid of its additional weight during it journey in space. That’s the reason we have stages.

On my next articles I would like to detail the upper stages of a high payload planetary rocket which are omitted by the others.

The Analyst

In recent years, I started to see more and more poorly designed product and services. I attribute the problem to poorly executed cost cutting measures and too much reliance on AI. The company's profit comes from the service they provide and the products they sell. Poor services and products result in reduced profits which intensifies the company’s cost cutting measures. In my opinion, the last place a company should cut costs should be the development of products and services. If this department is under employed and lower salary subpar employees are hired, then the company should prepare itself for bankruptcy or takeover.

From my observations, I conclude that the key role within a company is The Analyst. When analyses are made correctly which includes finding the alternative solutions, the success is inevitable. The complex engineering calculations and coding can be delegated to AI. However, it requires proper analysis which is a human task.

Analysis requires knowledge of many subjects. Good analyst doesn’t need to excel in any of them. However, need to be able to combine these knowledges whenever necessary. A good analyst should be able to ask the right questions to gather information which would guide him/her during his/her inductive reasoning, like Sherlock Holmes. When a company bases its products or services on successfully conducted analysis, the company would easily differentiate itself from the competition.

Previously, this role was assumed by non-engineers. AI has taken over most of the engineering tasks. As a result, new engineers should be taught to be good analysts who can look at the world from a wider perspective.

Better analysis solves more problems instead of creating new ones. This is beneficial for the societies that struggle in ever increasing number of problems.

Mars Research Base

I had recently proposed a Mars Lab Station. It would allow samples gathered all around Mars to be analyzed in orbit. However, transferring the samples from ground to the orbit requires single use expensive rockets. Sending one for every sample would be prohibitively expensive. I would like to propose an alternative based on my previous ideas.

A Mars Lab Base that would be deployed to a central location on Mars can serve as a stationary analysis base. The samples would be collected by the Mars STOL airplane. Once the samples are gathered, the aircraft would return to the base. The samples would then be transferred to the Lab using Mars Service Robot. The service robot would also conduct simple maintenance work for the aircraft. It would patch small holes, clean and oil parts.

The Lab Base, the aircraft and the service robot would utilize Plutonium 238 as the energy source. (explained in previous articles)

This setup requires at least three independent missions to Mars. One carrying the Lab Base, the second carrying the STOL aircraft and the last one carrying the service robot and maintenance materials. In order to cover more areas, these three missions would be repeated for each additional region.

Mars Lab Station

Mars rovers have limited payload. Therefore, they cannot conduct all kinds of analysis on the samples. That is why, Mars sample retrieval missions are planned. However, bringing samples to Earth requires big rockets with multiple stages. Such rockets do not exist at the moment. More importantly it takes months for a sample to reach Earth. During this time some of the samples may degrade even with proper preservation.

I propose a Mars Lab Station for robots only. It would orbit the planet like ISS orbiting the Earth. This lab would turn any sample retrieval mission to an LMO (Low Mars Orbit) mission compared to a mission from Mars to Earth. This would require much simpler retrieval rockets. Additionally, the samples would be processed much faster with minimal degradation. Finally, moving advanced lab equipment to the lab from the surface rovers would make the rovers simpler and more agile.

Mars has stronger gravitational anomalies than Earth. As a result, any orbiting object requires more maneuver and more fuel to stay in orbit. NASA had thought of missions to deploy satellites to Mars, but abandoned them all. However, establishing an orbital lab is more beneficial for the future compared to single shot missions to retrieve samples to be analyzed on Earth.

This idea can be generalized to other planets such as Venus and Mercury Lab Stations.

Mars Mission 1

I thought of a series of Mars missions which allow the humanity to gather much more information compared to the total of previous missions. The key to achieving this goal is to plan a bigger mission composed of smaller missions to achieve it. The key to explore more of Mars depends on the energy source of the surface explorers. Unfortunately, solar energy beyond Earth is very limited and creates a bottle neck for the missions. Like Earth, Mars also has day and night and seasons which dramatically affect the already low solar energy capacity.

I had previously proposed Plutonium 238 as the critical energy source for space missions. Previous space missions (to the moon) that utilized this isotope tried to generate electricity directly. This resulted in very poor energy conversion rates. However, Mars has atmosphere where Moon lacks. It is mainly carbon dioxide which has the highest vapor pressure of any gas. Heating the cold carbon dioxide gas with Pu₂₃₈ to generate pressure is very feasible. The generated pressure would be used to operate the pneumatic actuators and generate electricity. This method has way higher energy conversion efficiency compared to other methods and the solar energy. A proper planetary robot which has legs instead of wheels would be able to explore large areas on the surface of Mars. The additional explorations can be conducted on the shadows and at night. Even underground caves can be checked briefly. This method of electric generation would not be affected by the ambient temperature while it requires no chemical batteries. The consumable carbon dioxide gas is available all around the planet which pose no travel restriction. More energy means more distances can be travelled, drilling can be deeper and other energy intense tasks can be conducted.

On my next article I will explain how is it possible to analyze the Mars samples in detail.