Mars Flight Q&A

Executive Summary: I love science-fiction as much as anyone, but am shocked whenever I hear politicians, or social media fanboys, claim that Earth will be sending humans to Mars anytime soon. Our interplanetary travel desires are currently limited by the mathematics laid down by Konstantin Tsiolkovsky as they pertain to chemical-fueled rockets. Humans will go nowhere, other than our moon, until we develop a fission or fusion drive.

Technical Summary: This is one topic where many technical people are on the wrong side of the argument. They think that the technology used during "the Apollo manned missions to the moon from 1968 to 1972" can simply be scaled up for "a Human missions to Mars". Scientists familiar with the published works by Konstantin Tsiolkovsky already know that chemical-fueled rockets do not satisfy the Tsiolkovsky's Rocket equation as far as human-centric extra-planetary missions are concerned (comment: unmanned one-way flights are one thing, but adding humans is something completely different). We have heard colloquialisms like "It is not rocket science" for decades, warning us that "rocket science is hard". So I do not understand why everyone now thinks that sending humans to other planets will be easy.

This article is not finished (I have been called away to deal with other more pressing issues). But I have appended a few YouTube links by people who are much more qualified than me.

Questions & Answers

Will Americans put humans on Mars before China?
- I doubt it. Capitalistic English-speaking societies rarely do anything unless (1) there is money to be made (2) military use (3) political pride. The USA only went to the Moon to beat the Russians during the so-called Space Race. After 6 successful landings between 1969 and 1972, American politicians lost interest then cancelled the remaining flights. No government funding was ever made available to go back to the moon until China announced their intention to place taikonauts on the moon before 2030. Even today in 2026, Trump cut NASA's budget from US$20 billion to US$9 billion but still expects NASA to return to the moon by 2028 to coincide with his last year in office.
Will Humans put humans on Mars before 2199?
- I doubt it. The energy demands are too great, and this will not change until humanity moves beyond chemical rockets.
Why are the energy demands too great? Don't we just scale up our lunar technology?
- No. An Earth-Moon mission is totally different than an Earth-Mars mission.
- Moon
  - Since the Moon orbits Earth, humans can move between the Earth and Moon any time they wish.
  - The travel time will average 3-4 days (average distance: 240 thousand miles (386 thousand km)).
  - To move from Earth to the Moon, you need to partially climb out of Earth's gravity well, then partially coast down into the Moon's gravity well (which also happens to be a moving target).
- Mars
  - Since Mars orbits the Sun, humans can only travel between the Earth and Mars during a five-month launch window every two years. Remember that there are times when the Earth and Mars are on opposite sides of the Sun.
  - The travel time will average 9 months (and you will need to supply food and water
    - shortest distance: 34 million miles (56 million km)
    - longest distance: 250 million miles (401 million km)
    - remember that you will need to provide food and water for the whole mission (5 months there, perhaps 1 month on the ground, 5 months back).
      All this support material will increase you rocket's mass, and that will require a further increase in fuel (a.k.a. the Tsiolkovsky curse).
  - To move from Earth to Mars, you need to totally climb out of Earth's gravity well (which will leave you in the Sun's gravity well), then partially climb out of the Sun's gravity well before dropping into Mars's gravity well (which also happens to be a moving target)
  - Read this article for more details:
    - https://therocketscienceblog.wordpress.com/2018/07/01/how-to-get-to-mars/
- Moon Mission Philosophies
  - When Americans were planning the Apollo missions which would go to the Moon, they initially considered a technique known as Earth Orbit Rendezvous (EOR) where multiple Saturn 5 boosters would be required for each trip. The plan here was to launch a Saturn 5 with people and payload, then launch a second vehicle with additional fuel. One vehicle would need to rendezvous with the other (could be difficult with massive vehicles), then fuel would need to be transferred from one to the other. "in space". The folly of this technique was outlined by NASA engineer John Houbolt who suggested Lunar Orbit Rendezvous (LOR) as a more practical alternative.
  - With LOR you discard mass at every opportunity so, in the end, have a very low mass vehicle (the ascent stage of the Lunar Module (LM)) needing to find then rendezvous with a slight more massive Command Module (CM)) in Lunar Orbit. But in the case of an emergency, the CM was able to find then rendezvous with a LM if said vehicle was already in Lunar Orbit.
  - Apollo moon missions employed LOR and it barely worked.
- Mars?
  - The added mass to feed three or more astronauts for a 5-month mission to Mars (traveling there), then time on the ground, and 5-months back would required an enormous amount of additional fuel as outlined by the Tsiolkovsky Rocket equation (see below)
  - SpaceX has emphasized reusable technology where some of the launch fuel is reserved in order for booster soft-landing then recovery. Falcon is their current main workhorse while Starship is the much heavier alternative intended for use on the Moon and Mars. As I write this on 2026-03-14, Starship has not been able to reach orbit with zero payload let alone anything useful. Once they get this working, they plan to use Earth Orbit Rendezvous to deliver fuel to the primary vehicle. At this point in time, each single Moon mission might require many multiple refueling events (some have suggested that more than 10) because they intend to land a much heavier vehicle on its tail on the moon. This might never work which is why interim mission planners had suggested a small space station called Lunar Gateway (get people to the Gateway; descend to the moon's surface in much less massive lander; then have that lander return back to the Lunar Gateway) which might not survive Trump's budget cuts.

Rocketry Basics

All rocket technology begins with Newton's Second Law of motion:
     F = ma
Legend:
     F = force, m = mass, a = acceleration.
Since "a" is defined as change in velocity over change in time, F=ma can be rewritten as:
     F = m (dv / dt)
alternatively:
     F = m (Δv / Δ/t)
This algebraic equation can be rearranged further to produce a quantity known as Impulse:
     F dt = m dv
alternatively:
     F Δt = m Δv

short summary

So to get any rocket moving forward, you need to eject a reaction mass in the opposite direction (the rocket engine pushes against the rocket exhaust)
The rocket's mass should be as low as possible while the reaction mass must be as fast as possible.
With chemical rockets, the reaction mass is, obviously, a burning chemical which is a process that derives energy by rearranging electrons.
If you want increased thrust length (eg a longer burn) you will need more fuel which will require larger fuel tanks which will increase the rocket's mass.
If you want increased thrust, then you will need larger engines, or employ a better fuel. Larger engines will increase the rocket's mass.
If you want your boosters to be reusable (we all love what SpaceX has done in this area with boosters soft-landing close to their launch points) you will need to set aside some fuel which would normally have been used to get a payload into orbit. Here was are exchanging launch efficiency for reusability.
from Gemini AI: Chemical rockets are highly efficient thermal engines, often exceeding 60% thermal efficiency, but they have low propellant efficiency (specific impulse, or Isp), typically ranging from 240s to 450s. They offer high thrust essential for lifting heavy payloads through Earth's atmosphere, but are inefficient for in-space maneuvering compared to ion engines.

Konstantin Tsiolkovsky

In 1903 while the Wright brothers were proving that a motorized bicycle air frame could fly, Konstantin Tsiolkovsky published "Exploration of Space Using Reactive Devices" (part 1) in the Russian publication Nauchnoe Obozrenie (Scientific Review). This is the first time he published what is now known as the Tsiolkovsky Rocket Equation which is the basis for all rocket technology used today as it places limits on both rocket mass (empty vs.fully fueled) and rocket payload which is part of the empty mass. The rocket formula contains an ln() function which represents a logarithm to the base of e (e.g. so a natural logarithm) which basically means that trying exponentially harder will only yield a linear result.

Here is a little blurb from Google's Gemini AI:
question: explain the ln function in the Tsiolkovsky rocket equation
answer: The ln() function in the Tsiolkovsky rocket equation represents the natural logarithm, which models the diminishing returns of fuel efficiency as a rocket becomes lighter. It calculates the necessary mass ratio to achieve a specific velocity change, accounting for the fact that extra fuel must lift itself.

What ln Represents: It is the inverse of the exponential function, accounting for the exponential growth in fuel needed to achieve linear increases in speed (Δv).
The Mass Ratio: The input to the natural log is the ratio of initial mass (m0), including propellant) to final mass (mf), dry mass). A higher ratio means more fuel is available relative to the payload.
Diminishing Returns: Because ln(x) grows slowly, adding massive amounts of fuel results in smaller and smaller gains in speed. Doubling the fuel doesn't double the speed; it only adds a constant, smaller velocity boost.
Summary: In essence ln() shows that while you can increase speed by carrying more fuel, the weight of that fuel eventually limits how much extra speed you can get.

Chemical vs Nuclear

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Chemical Reactions: are all based upon energy differences of electrons. The range is usually given in single electron volts which is why a carbon-nickel flashlight battery yields ~ 1.5 volts.

Nuclear Reactions: These come in two forms:

fission: involves splitting the nucleus of large atoms greater than the mass of Iron (mimics natural radioactive decay)
fusion: involves the fusing of nuclei of small atoms lighter than iron (mimics the natural energy production of stars like our Sun)