If one small (Prometheus-class) nuclear reactor is available, a complete human Mars mission becomes available with two Saturn V-class boosters. The book
The Case for Mars fully explains this, as does this
website, but I will summarize the main concepts of the Mars Direct plan here.
First, a Saturn-V class booster launches a 40-tonne unmanned payload to the surface of Mars on a 258-day Hohmann transfer. This craft, called the Earth Return Vehicle, or ERV, lands at the future landing site of the human Mars mission. It is an unfueled methane/oxygen propellant two stage ascent and Earth return vehicle. It lands with a 100 kWe nuclear reactor, a light truck, a set of compressors, and a chemical processing unit. The truck is telerobotically driven a few hundred meters away, and it deploys the nuclear reactor which will power the chemical processing unit. Six tonnes of hydrogen are brought from Earth, and it is reacted with Martian carbon dioxide to produce methane and water. The water is electrolysed to provide oxygen, both as air for the crew and as propellant, and the hydrogen is recycled into the system. This produces 48 tonnes of methane and 24 tonnes of oxygen. Martian carbon dioxide is disassociated to provide 36 more tonnes of oxygen. 108 tonnes of methane/oxygen propellant is now available, as is nine tonnes of water. 96 tonnes of propellant will be used to fuel the ERV, and the remaining 12 tonnes are available for internal combustion engine rovers. Now, from one Saturn-V class booster, we have a fully fueled Earth Return Vehicle, complete with water and air, waiting for the crew on Mars, one which has survived a landing.
Twenty-six months later, in the next launch window, two more Saturn-V class boosters are sent towards Mars. One carries another ERV for the next landing site, and the other is a "Hab", the crew's vehicle. It carries a crew of four, an internal combustion pressurized rover, two light rovers, and 500 kilograms of scientific equipment (500 more are on the ERV, making for a total of
one thousand kilograms of scientific equipment).
Provisions for three years are carried. After launch, a cable is extended between the Hab and the upper stage of the booster, providing artifical gravity. The total mass of the Hab is 28 tonnes and it can be sent on a 180-day trajectory.
This is an extremely safe plan. The crew has a rover with a one-way range of 1,000 kilometers if they do not land right next to the ERV. Even if they land on the other side of the planet, the second ERV can be targeted to land near it. Even if both of them miss, the crew has provisions for thee years and can just wait until another ERV can be sent out. The plant is extremely robust.
The crew stays on the surface for 1 1/2 years, and there is ebough rover fuel available for about 22,000 kilometers of traverses. Thus, each mission can explore about 800,000 square kilometers during their stay. The Mars Direct harware can be easily modified to accomplish lunar missions, also.
So, we have a complete Mars exploration mission with nothing more than two Saturn Vs, some chemical engineering that has been around for over a century, and some present-day technology. No fantastical schemes are required for a Mars mission. We can do this, now.
So what was it that you were saying? :wink: