Mars Flight Q&A

Executive Summary: I love science-fiction as much (perhaps more) than most people, but am shocked whenever I hear politicians, or YouTube fan-boys, claim that Earth will be sending humans to Mars anytime soon. IMHO, our desires are currently limited by the mathematics laid down by Konstantin Tsiolkovsky as it pertains to chemical rockets. We will go nowhere, other than our moon, until we develop a fission or fusion drive.

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.
- Mars
  - Since Mars orbits the Sun, humans can only travel between the Earth and Mars during a five month launch window every two years. There are times when the Earth and Mars are on opposite sides of the Sun.
  - The travel time will average 9 months
    - shortest distance: 34 million miles (56 million km)
    - longest distance: 250 million miles (401 million km)
  - To move from Earth to Mars, you need to totally climb out of Earth's gravity well, then partially climb out of the Sun's gravity well before dropping into Mars's gravity well
  - Read this article for more details:
    - https://therocketscienceblog.wordpress.com/2018/07/01/how-to-get-to-mars/

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

paragraph outline [[[ TODO: fill in then correct this section ]]]

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)