journey. The distance between Earth and Mars varies from 35 to 93 million miles.
To reach the red planet using current rocket engines and not Hollywood special
effects, astronauts would have to travel not less than 7 months on a spacecraft that
uses the gravitational forces of the planets, accelerating and slowing down in the
solar system and then arriving on the red planet with enough fuel to go back with
another 7 months flight. This type of mission is quite feasible with a robotic probe
powered by a nuclear radioisotope thermoelectric generator that ensures power in
all conditions, but the situation becomes dramatically complicated if a spaceship
hosts human beings who need to be protected by the radioactive decay of plutonium-238. The drastic reduction of travel time is therefore one of the current main
objectives, but unfortunately, there is very little progress in this area.
NASA has been supporting for years the efforts of the company Ad Astra
Rocket, founded by former astronaut Franklin Chang-Díaz, which has been
designing for years a plasma engine called the Variable Specific Impulse Magneto
Plasma Rocket (VASIMR),
36
in which radio waves heat up a gas and bring it to a
state of plasma, which produces a propulsive thrust through a powerful magnetic
field. In theory, this engine could propel a spaceship to Mars in just five months if
it was fed by a power of 200 megawatts, equivalent to that of a medium-sized
thermal power plant. NASA has funded a 100-kilowatt
37
prototype with $10 million – still far from the power needed to reach the red planet.
Another engine whose first results appear promising is the X3,
38
an ion thruster
that could really be used for a mission to Mars in the future. Even in this case, the
thrust is given by a gas, xenon, heated by electromagnetic fields fed by a power
device. Today, these engines run on 5 kilowatts, but NASA plans to increase the
impulse soon with a power supply of over 100 kilowatts, although still far from the
700 kilowatts needed to reach Mars. Since the X3 was funded by the Air Force and
not by NASA, it is plausible that within a decade, this engine will be used on military spacecraft and only afterward for interplanetary travel as well.
Furthermore, engineers will have to solve the problem of cosmic radiation, to
which astronauts traveling to Mars would be subjected. According to NASA, each
of them could assume an amount of radiation equal to 66 rems in a year – a dose
equivalent to a computed tomography scan every week. After six months on the
ISS, an astronaut absorbs about 10 rems, with a statistical increase in developing
potential forms of cancer of 3% – the maximum allowed by NASA. Based on this,
it seems clear that the only option for traveling to Mars while sparing the astronauts from radiation would be to design an unlikely spaceship with lead and concrete panels. More realistically, it will be necessary to develop innovative
36
http://www.adastrarocket.com/aarc/VASIMR.
37
http://www.industrytap.com/nasas-new-vasimr-plasma-engine-reach-mars-39-days/33646.
38
https://www.space.com/38444-mars-thruster-design-breaks-records.html.
130 Mars: Next Stop?
To reach the red planet using current rocket engines and not Hollywood special
effects, astronauts would have to travel not less than 7 months on a spacecraft that
uses the gravitational forces of the planets, accelerating and slowing down in the
solar system and then arriving on the red planet with enough fuel to go back with
another 7 months flight. This type of mission is quite feasible with a robotic probe
powered by a nuclear radioisotope thermoelectric generator that ensures power in
all conditions, but the situation becomes dramatically complicated if a spaceship
hosts human beings who need to be protected by the radioactive decay of plutonium-238. The drastic reduction of travel time is therefore one of the current main
objectives, but unfortunately, there is very little progress in this area.
NASA has been supporting for years the efforts of the company Ad Astra
Rocket, founded by former astronaut Franklin Chang-Díaz, which has been
designing for years a plasma engine called the Variable Specific Impulse Magneto
Plasma Rocket (VASIMR),
36
in which radio waves heat up a gas and bring it to a
state of plasma, which produces a propulsive thrust through a powerful magnetic
field. In theory, this engine could propel a spaceship to Mars in just five months if
it was fed by a power of 200 megawatts, equivalent to that of a medium-sized
thermal power plant. NASA has funded a 100-kilowatt
37
prototype with $10 million – still far from the power needed to reach the red planet.
Another engine whose first results appear promising is the X3,
38
an ion thruster
that could really be used for a mission to Mars in the future. Even in this case, the
thrust is given by a gas, xenon, heated by electromagnetic fields fed by a power
device. Today, these engines run on 5 kilowatts, but NASA plans to increase the
impulse soon with a power supply of over 100 kilowatts, although still far from the
700 kilowatts needed to reach Mars. Since the X3 was funded by the Air Force and
not by NASA, it is plausible that within a decade, this engine will be used on military spacecraft and only afterward for interplanetary travel as well.
Furthermore, engineers will have to solve the problem of cosmic radiation, to
which astronauts traveling to Mars would be subjected. According to NASA, each
of them could assume an amount of radiation equal to 66 rems in a year – a dose
equivalent to a computed tomography scan every week. After six months on the
ISS, an astronaut absorbs about 10 rems, with a statistical increase in developing
potential forms of cancer of 3% – the maximum allowed by NASA. Based on this,
it seems clear that the only option for traveling to Mars while sparing the astronauts from radiation would be to design an unlikely spaceship with lead and concrete panels. More realistically, it will be necessary to develop innovative
36
http://www.adastrarocket.com/aarc/VASIMR.
37
http://www.industrytap.com/nasas-new-vasimr-plasma-engine-reach-mars-39-days/33646.
38
https://www.space.com/38444-mars-thruster-design-breaks-records.html.
130 Mars: Next Stop?