Mars mission and artificial gravity.

Artificial gravity is one factor that can make interplanetary spaceflight possible. One of the simplest ways is to use centripetal force to create that effect. In those models. Here are two capsules connected with Kevlar wire. Those capsules rotate around their center of mass. That creates artificial gravity in those capsules. Some researchers say. The centripetal force is not enough to create 1G artificial gravity. When. Researchers talk about artificial gravity. They don’t necessarily mean that the system must make gravity as strong as Earth's. That means artificial gravity might mean. A situation.  Where people can put cups on the table. And. The cup stays on the table.

Artificial gravity is good for mental health. It is required. To keep muscles as strong as possible. Without gravity, space travellers lose their muscles. And the other thing is that. Their bones become weak. When. We plan the Mars journeys. Those things require complete planning. And precise cooperation. Between all parts of the system. Even a small problem can be fatal in the spacecraft. That travels between Earth and Mars. In the case of accidents. The spacecraft must travel to Mars. There, it can use Mars as a gravitational sling. And return to Earth. 

When the craft travels to Mars. 

It needs to win the Sun's gravity. When it returns to Earth, it must also slow its speed at the right point. It must slow its speed enough to land safely. Breaking the system is as difficult as accelerating the system. When. The nuclear rocket sets itself to Mars orbit. That process is more difficult. Than. setting. Some 1-ton spacecraft into Mars orbit.  

“The concept of a tether between two large masses is the cheapest, least resource-intensive way to create an artificial gravity environment that could house human astronauts in outer space. But whether this type of technology is ready for prime time or not depends on whether our engineering capabilities are up to the challenge of maintaining stability at sufficiently large tether distances to make the environment hospitable to humans.” (BigThink, Ask Ethan: Can a Kevlar tether create artificial gravity in space?)



The minimal concept is this. 



 Advanced Nuclear Thermal/Electric Propulsion (NTP/NEP)

NASA's formal Mars Design Reference Architecture (DRA 5.0) and parallel peer studies heavily favor nuclear propulsion because it reduces the required fuel mass.
• Total LEO Mass: ~250 to 400 metric tons.
• Example Concept: A realistic 2035 Nuclear-Electric Propulsion (NEP) design outlines a 250-ton vehicle featuring:
 • Crew Transport Vehicle (CTV): 20 metric tons.
 • Mars Lander: 65 metric tons.
 • Xenon Propellant: ~75 metric tons.
 • Power Plant: 3 x 1 Megawatt nuclear reactors


But. There are. Many. Problems with that operation. Mars must be in the right position relative to Earth. The spacecraft must wait for the launch window. That allows the Mars craft to return to Earth. When. The craft returns to Earth. It must slow its speed at the right moment. So. The craft can return to Earth orbit. There, the shuttle can bring astronauts back to Earth. But the fact is that. It’s easier to slow mass less than 20 tons. Than to slow and control a mass of at least 100 tons. This means that Mars craft can have a return capsule that returns to Earth orbit. The craft can leave a manned landing module to the Mars orbiter. If. It follows the same formula as the Moon mission. 

Another possibility is a so-called fly-by mission. The Mars craft returns to Earth, flying past the Earth and Moon. At the right moment, the craft releases its return capsule. That should happen behind the Moon. The brake rockets and the Moon’s gravity field will slow the capsule. In the last scenario, the system slows the entire craft. It slows the entire craft’s speed. Also, shuttles that observe the operation can assist the capsule. That returns the crew to Earth. 

Before it returns. The. Life-support capsule will be separated. The main components, like nuclear reactors, are in the main rocket. The small capsule is easier to maneuver. The rocket's weight. It is at least about 10,000 tons. The smaller return capsule is always easier to maneuver. And if the main rocket maneuvers, it can fail. And radioactive debris will not pollute Earth. The bigger rocket can continue its journey to the Sun. 



https://bigthink.com/starts-with-a-bang/kevlar-tether-artificial-gravity-space/



https://www.sciencedirect.com/science/article/abs/pii/S0094576515002891