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MANNED MISSION TO MARS

A giant leap for mankind: If you think of the most important achievements of the 20th century, thoughts go to the landing on the moon in 1969. But which event will be remembered in 100 years? All over the world scientists and space agencies are working on the answer: a manned mission to the neighbouring planet Mars might be the next big jump into the universe for us.

If current plans can be put into practise, man will be able to leave his footprint on Mars in 2019 to celebrate the 50th anniversary of the moon landing. If humanity really wants to land on the Red Planet in two decades, a program has to be in place by 2008 at the latest if one takes into consideration that the predevelopment phase will take ten years and that the actual flight to Mars almost one year.

The development of a suitable transport craft will be especially expensive. This craft will have to transport six astronauts and landing and return vehicles to Mars. Since the Mars ferry is particularly big, it cannot be transported into space with just one launch. It will have to be assembled in the Earth's orbit.

The payload capacity of existing rockets and carrier systems like the American Space Shuttle or Ariane 5 with about 20 tonnes will not suffice. For a manned Mars mission these rockets would have to be used about 50 times. A carrier rocket of the Saturn-V-Class, which transported the first human to moon and which is now unfortunately obsolete, would be ideal.

Today one might consider a Space Shuttle, which has been converted into a heavy load transport craft, the so-called Shuttle-C (Cargo), where the manned, winged orbiter is substituted by a cylindrical non-winged freight container. After some slight modifications Shuttle-C might then boast a freight capacity of up to 100 tonnes. Only about ten flights would be necessary to assemble the Mars ferry.

After the ten year development program for the Mars ferry has been completed successfully and a crew has been selected, the individual stages of the ferry will be transported into Earth's orbit along with the previously discussed carrier rocket.

They are linked up in Earth orbit, fuelled and prepared for the take off to Mars. Fully fuelled the Mars ferry has a mass of about 1,000 tonnes. Over two thirds of this is fuel. It would then be the biggest space craft by far to have ever been constructed by humans in space.

As soon as assembly in orbit has been completed, the six crewmembers will enter the Mars ferry. The crew might be transported to the Mars ferry, which is ready for take off in orbit, by the winged Space Shuttle supported by the Russian Sojus Carrier Rocket, if these carrier systems are still in use then. Or a carrier system based on Ariane 5, which still needs to be developed, might be used for this purpose.

In order to reach the interplanetary transfer course to Mars, the four huge engines with a thrust of 420 tonnes will be fired for almost ten minutes. The Mars ferry will be accelerated to a speed of 40,000km/h relatively to Earth with the help of this thrust. This is the so-called escape velocity that enables the craft to leave the Earth's gravitational field.

A few days after taking off from the parking orbit, over one million km have been covered, the Mars ferry leaves behind the Earth's gravitational forces and enters the interplanetary route on an orbit around the sun. In order to reach Mars on a course requiring as little energy as possible, the crew carries out half an orbit around the sun in free flight. In doing this it covers about half a billion kilometres.

A few days before arriving on Mars, the crew split up. Four of the six crew members enter the Mars landing stage in order to disconnect from the mother ship. The two craft cover the rest of the trip to Mars separately. Technical analyses have shown that in this way ten per cent of craft mass can be saved.

After about 260 travel days both craft reach their target Mars, and one of the most critical and dangerous phases of the mission begins: the safe entry into the parking orbit around Mars. In order to achieve this, the mother ship and the landing stage have to reduce their speed by several thousand km/h, if they are not to overshoot Mars and possibly get lost in an orbit around the sun. Detailed research has shown that a lot of fuel can be saved if the air resistance of the Martian atmosphere is used to reduce the speed.

Both spacecraft will enter the Martian atmosphere at an altitude of about 50km at a safe distance from each other and at a speed of 20,000km/h. The large thermal protection shield in front of the spacecraft will be glowing red, this is caused by frictional heat. After only a few minutes both spacecraft will have slowed down to orbital speed. The engines will then be fired again in order to fly to a higher, more stable parking orbit outside Mars' atmosphere.

The crew of the Martian landing stage now has one last chance to check all systems before landing. Thanks to the existence of the thin atmosphere on Mars, the slowing down effect of the atmosphere can again be used to reduce the craft's speed and save fuel for landing. The Martian landing stage, onto which the markedly smaller return vehicle is docked piggyback-fashion, ignites the deceleration engines after which it enters the upper layers of the Martian atmosphere at an altitude of roughly 50km.

The landing stage now loses altitude and speed constantly. About five kilometres from the touch down site the initial speed of 17,000km/h is reduced to about 4,000km/h, and the crew jettisons the heat shield. The four symmetrically located engines are ignited to steer towards the touch down site with precision.

Shortly before this site is reached, the landing gear is extended and the craft puts down softly on the surface of Mars. The first humans have landed on Mars! Everyone on board gets very busy now. The crew immediately checks all systems of the Martian landing stage, which has to give safe accommodation and guarantee survival in the hostile surroundings on the surface of Mars.

Once all systems work without a hitch, the first humans will step onto the surface of the Red Planet. Since the atmospheric pressure is very low, it is comparable to the Earth's atmosphere at 30km altitude, the astronauts wear a light space suit with life support system during their stay outside. Gravity is only a third of that on Earth.

After a first exploration in the immediate vicinity, work on the extensive scientific program is started. Rock and soil samples are collected and analysed in the laboratory. Furthermore seismograms are being made to explore the tectonics of Mars.

The palaeontologist and biologist looks for fossils in rock and in drilling samples and tries to find life, which might still be there today in warmer areas, where the permafrost has melted. Long term biological experiments, i.e. growing of plants in the Martian soil and tests for radiation exposure are set up to prepare the technology for a closed biological system (greenhouse). This would make future missions somewhat more independent from expensive transports from Earth.

The experimental running of production plants to generate fuel for the return journey for later missions would serve a similar purpose. It would be possible to profit from the natural resources on Mars, by creating oxygen from the carbon dioxide atmosphere and by adding hydrogen methane, the rocket fuel, could be generated.

Since the length of stay is considerable, (in our example 415 days), far reaching excursions (100km and further) could and should be carried out with a pressurised rover. These expeditions would increase the scientific value of the mission considerably.

After more than 400 days - longer than half a Martian year and more than one Earth year - the time to return has come. Because of the different speeds in which Mars and Earth orbit the sun, there is a first opportunity to launch the craft for her trip back to Earth. This window allows an interplanetary fuel saving return flight to the home planet.

Take off from the surface of Mars requires a speed of about 20,000km/h. This will be the most fuel intensive part of the entire mission. All four engines of the lift off stage will be ignited, and the stage will lift off the surface of Mars. The craft will aim for a safe transfer orbit around Mars near the mother ship within a few minutes. After a careful approach and successful docking the crew will enter the mother ship.

They will be welcomed here by the crew, who have stayed behind orbiting Mars and who have studied Mars from afar and ensured that the mother ship was functioning perfectly. The latter is now to return all six astronauts safely to Earth.

In order to keep the take off mass low and save fuel, the mother ship undocks the return vehicle, which is no longer needed. It also jettisons the heat shield. As soon as the signal is given from the ground station on Earth, the interplanetary mother ship ignites her two main engines for the last time for about 100sec in order to increase her speed by more than 3,000km/h and to enable her to leave Mars' attractive force.

Almost 300 days after leaving Mars our blue home planet is clearly visible again. It is the size of the Earth's moon. The mother ship reaches the Earth's attractive force within the next few days and gathers speed because of the gravitational force. A few hours before entering into Earth's atmosphere the crew changes into the reentry capsule. Some last finely tuned course corrections are especially important and critical during this flight phase. Only if the capsule enters the atmosphere within a very narrowly defined entry corridor, will the crew reach the Earth's surface unharmed.

A few minutes before the upper layers or the Earth's atmosphere are reached at an altitude of about 120km, the capsule separates from the mother ship. While the mother ship burns out in the atmosphere, the capsule enters the Earth's atmosphere at a speed of 40,000km/h, if everything goes according to plan. Because of the enormous aerodynamic friction heat at the deflector heat protection shield, the capsule is surrounded by a red glowing fire ball, and radio contact to the ground is interrupted for a short time.

For a last time the crew is subjected for a short time to a pressure, which is six to ten times their body weight, because of the tremendous aerodynamic drag. A few minutes later with the support of several parachutes the capsule lands softly on the Earth surface. After having travelled for almost 1,000 days the crew is back.

From page 40 of FLUG REVUE 12/99