Mars tugs at human curiosity more than any planet. More because of the many similarities that Earth shares with the Red Planet and its proximity. One of the many questions that are often asked is this: If we explore the evolution of Mars, will that tell us something about the Earth itself? The other important motive for exploring Mars is the eternal search for evidence of past or present life. Last but not least, the romance of the science-fiction writer is to create habitat on another planet. As Carl Sagan said, "Staying alive … When our long-term survival is at stake, we have a fundamental responsibility for our species to venture into other worlds and guarantee not only human survival, but humanity for always!" 1
Long-term human spaceflight presents a series of difficult challenges; Unlike robots, people need to be nourished, hydrated, protected, entertained, and above all, they must be brought home safely. There is a saying, "Everything is difficult until you do it". Similarly, "Without knowing what to do, we can do nothing". Here is an attempt to enumerate the key challenges of a manned mission on Mars: mission design, propulsion system requirements, human health, in-situ resource utilization (ISRU), crew autonomy, power supply, system reliability and landing and advancement.
manned missions ahead of a series of pilot missions (at least 3 to 6). Pilot missions consist mainly of freight missions and an Earth Return Vehicle mission. Freight flights shall include a lander with a Mars ascent vehicle (MAV) and additional supplies consisting of housing units, life support units and supply units. This sequence is gradually building assets on the Martian surface, so that at the end of the cargo flights, the base infrastructure could be present. More freight launches may be required to install crew securing systems. An unmanned rover mission can also be proposed that will be launched to Mars to locate a landing pad.
Freight missions could use aerobraking or aerocapture techniques to minimize MOI fuel requirements. Aerobraking is a space flight maneuver that reduces the altitude of an elliptical orbit (apoapsis) by flying the vehicle through the atmosphere at the lower end of the orbit (periapsis). The resulting drag slows down the spacecraft. Aerobraking is used when a spacecraft needs a low orbit after it has arrived at a one-atmosphere body, and it requires less fuel than the direct use of a rocket engine.
Aerocapture is a related but more extreme method in which no initial orbital burning process is performed. Instead, the spacecraft dives deep into the atmosphere without an initial burn-in, and exits this single passage in the atmosphere with an apoapse near the desired orbit. Several small correction burns are then used to raise the periapsis and make final adjustments. Another related technique is that of aerogravic support, in which the spacecraft flies through the upper atmosphere and uses aerodynamic lift rather than drag at the point of closest approach. When properly aligned, this can increase the angle of deflection beyond that of a pure gravitational assistant, resulting in a larger delta-v.
The crew must fly in relatively fast transits (4 to 6 months) and from Mars to Mars will spend long periods of time (18 to 20 months, 600 days nominal) on the surface, rather than alternative approaches that take longer. Shorter transit times reduce the time the crew spends in weightlessness. In addition, relatively fast transits will reduce exposure to galactic cosmic rays and the likelihood of encountering solar particle events. Reducing exposure to weightlessness and radiation events helps to reduce the risk to the crew.
In order to improve communications with the crew after Mars landing, it is also possible to launch a communications satellite that allows for continuous communication with the future landing asset. An isostatic orbit or an isosynchronous equatorial orbit is a circular, isosynchronous orbit in the Martian equatorial plane about 17,032 km above the surface, at any point that revolves around Mars in the same direction and period as the Martian surface. The Areostationary orbit is a concept similar to Earth's geostationary orbit. The basic propulsion system used for Mars trans injection is a LOX / LH2 propulsion stage above the launch vehicle. To transfer from LEO (Low Earth Orbit) to Mars with LOX / LH2 propulsion, about 55% (or 65%) of the LEO mass is needed for the fuel and propulsion stage and 45% (or 35%) for the LEO Mass in LEO consists of payload that is sent on the way to Mars.
For Mars, the actual drive demand depends on several factors, such as: B. the specific launch option and the desired duration of the trip to Mars. One can either use a lower energy trajectory with a tripping time of typically 300 ± 400 days requiring less fuel (suitable for cargo transfer) or a higher energy trajectory consuming more fuel with a tripping time of typically 170 to 200 days ((19659002) The LOX / LH2 is the most efficient form of chemical propulsion available, and the technology for using the LOX / LH2 propulsion to take off the planet is pretty mature, although LOX / LH is the most efficient form of chemical propulsion Requiring that three mass units in LEO be required to send a mass unit on the way to Mars, a major factor in driving forward the LEO initial (IMLEO) for Mars missions, the use of core-temperature rockets (NTR) partially mitigates this high demand. If a nuclear thermal drive (NTP) is used for the departure of the earth, two important factors are the min Imale height, which is allowed for the start and the dry mass fraction of the drive system. The use of NTP instead of LOX / LH2 for the departure of the earth can reduce the initial mass in the lower Earth orbit (IMLEO) by 40%.
Another option is the use of an electric solar drive for orbital lift. A solar electric propulsion system could be used to raise the LEO spacecraft's orbit to a high Earth orbit and thereby greatly reduce the propulsion requirements for the departure of the earth. Furthermore, the chemical drive is used from an elongated elliptical orbit and the trans-Mars injection in this case requires much less propellant. The energy that would have been used to exit LEO with chemical propulsion is largely replaced by solar energy, which powers the electric propulsion system used to place spacecraft in high orbit.
These options could be used to transport assets to Mars Surface Travel time is much longer. Also, aero-assisted Mars orbit launch and entry, departure and landing may be required for the cargo missions
(Mylswamy Annadurai is director, UR Rao Satellite Center – formerly Isro Satellite Center, Bengaluru )  end-of