Artemis 1: En route to the Moon again,but this time to stay there!
The journey to the Moon is surely the most extreme ever undertaken by a human being.
It is incredible to think how the Apollo astronauts managed to reach our satellite
aboard a spacecraft whose onboard computer had the computing power of a pocket calculator.
Despite the technological limitations of the time, they were able to demonstrate
the feasibility of a journey until then considered impossible. Today,
more than fifty years later, with Artemis 1 we are preparing again to make this incredible crossing.
We will use the same trajectories born in that golden age of space exploration,
but we will have the support of much more advanced knowledge in the field of astrodynamics that will
allow us to exploit in a much more efficient way the gravitational laws of orbital mechanics. And
in the near future, such a journey may become less and less exceptional, and more and more normal.
But never entirely easy and without danger! Unlike atmospheric flight,
space flight is in fact characterized by extremely limited freedom of movement.
If an airplane can reach the same destination by making hundreds of different routes,
the routes to the Moon are much less. The reason is that the motion of bodies in space is bound to
very precise laws dictated by gravitation. Exploiting these laws, the engineers of the
Apollo program studied in the sixties, for the first time, the transfer trajectories
to the Moon that are still used today. But the Artemis Mission will travel new ones.
Believe me. It will be a return to the "Apollo Spirit",
it will be something formidable, not to be missed. So what would you say, in order not to be caught
unprepared by the events and to follow at best a three-week space adventure, to do together a nice
review of all phases of the mission? Would you like to?
The exact day we do not know yet, but now we are sure to be in the home stretch. Whether it
will be in next December or January, soon will finally start the mission that will open the
doors of human exploration of the Solar System. From Launch Complex 39B at Kennedy Space Center
is in fact about to be launched Artemis 1, which in addition to being the first
mission of the Artemis program, will also be the first flight for both the heavy Space Launch
System and the Orion capsule. Precisely because of the need
to still test these means, onboard Artemis 1 there will be no astronauts. As a result, life support,
displays, and control instrumentation have been removed from the capsule. In its place have
been inserted sensors and scientific instruments capable of detecting every single parameter inside
the capsule, such as radiation levels, pressures, and temperatures. Onboard, however, there will be
dummies, on which sensors are placed to monitor all the levels of radiation they will undergo.
The name chosen for the main dummy ("Commander Moonikin Campos") pays homage to the famous
engineer of the Apollo 13 mission, the one who played a key role in bringing back safely to Earth
the astronauts Jim Lovell, Jack Swigert, and Fred Haise, after an explosion in the service module
not only thwarted the moon landing but also put a strain on the simple re-entry.
Moonikin Campos will wear the same spacesuit that will be used by the astronauts and will
be equipped with a series of sensors that can measure several useful parameters,
such as the values of acceleration during the various phases of the trip,
the vibrations to which the crew members will be subjected and the level of radiation. Campos will
not be alone, to keep him company there will be Zolgar and Helga,
two human torsos similar to those normally used for simulations of ballistic trauma.
The service module, which will provide propulsion, electrical power, temperature control,
and life support to the crew module, will be developed by the European Space Agency.
The Space Launch System rocket is designed for missions carrying crew or cargo to the
Moon and beyond, and will produce 4 million kilograms of thrust during liftoff and ascent
to carry a vehicle weighing 2,700 tons into orbit. Lifted by a pair of boosters and four engines,
the rocket will reach its period of maximum thrust within ninety seconds. After throwing the
boosters, service module panels, and launch abort system overboard, the main stage engines will shut
down and the main stage will separate from the spacecraft, consisting of the Orion capsule, the
European Space Agency-provided Service Module, and the rocket's second stage (the Interim Cryogenic
Propulsion Stage). The ESA module is placed under the actual capsule, and will accompany it
throughout the journey to and from the Moon. Only before Orion returns to Earth this module
will be undocked. Inside are the capsule's main engines, gas and propellant tanks,
and various secondary engines. The Space Launch System will bring the
Orion capsule, together with the second stage and the, into a parking orbit at an altitude of about
200 km. After a couple of revolutions around the Earth, at the appropriate time will be deployed
the solar panels and then turned on the engines of the second stage, which will produce an increase
in speed that will allow the spacecraft to leave the parking orbit. This maneuver is called
Transfer Lunar Injection and it will bring the spacecraft on the right course towards the Moon.
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The Transfer Lunar Injection is one of the most critical phases of the mission. The timing in
the ignition of the engines is in fact essential to intercept the Moon along its orbit around the
Earth. In this way, the spacecraft can enter the lunar gravitational sphere of influence,
a region of space in which the attraction of our satellite is dominant compared to that
of the Earth. A delay (or an advance) of a few minutes in the Transfer Lunar Injection maneuver
can lead to a trajectory error such that the spacecraft will not enter the lunar gravitational
sphere but will be lost drifting beyond the orbit of our satellite. The exact moment in which to
start the engines to perform the Transfer Lunar Injection is for this reason calculated with great
care by the engineers in the years before the mission, taking into account the lunar motions.
After this real topical moment, the third stage will be abandoned and the phase of the trip,
called Transfer Lunar Orbit, will start, which within three days will bring the capsule
insight of our satellite. At that point, the engines will be turned on again to slow down the
spacecraft and to put it into circumlunar orbit. This maneuver is called Lunar Orbit Insertion.
There may be slightly different trajectories depending on the mission but in any case,
the approach used is the one just described for a simple reason: the safety of the crew.
In case a malfunction of the propulsion system prevents the spacecraft to enter into lunar orbit,
with this type of trajectory the spacecraft will be able to return to earth spontaneously, without
the need of any propulsive action but simply using the lunar gravity with a Gravity Assist maneuver.
In this case, we speak of the Free-return trajectory.
The Apollo missions from 8 to 11 all flew on this type of trajectory, while the subsequent ones
used hybrid trajectories. The reason for this change was that the free-return trajectories,
while safer, only allowed descent to the Moon at the equatorial region. Since the
landing sites of the missions following 11 were located at higher latitudes,
it was necessary to adopt this type of solution. In a hybrid trajectory, the spacecraft initially
flies a common free-return, but during the crossing it is abandoned to enter an optimal
trajectory depending on the desired landing site. As soon as the free-return is abandoned,
the spacecraft loses the great advantage of being able to count on a spontaneous return to earth.
The idea behind this strategy, which was used in the Apollo program, was to remain on a free-return
orbit until all systems were verified and it was ensured that there was no malfunction.
If any anomaly had occurred during these checks, the spacecraft would still have
been able to return spontaneously by performing a fly-by with the Moon.
After checking the status of all systems, the free-return was abandoned and the spacecraft would
enter on a different trajectory that would allow it to reach the predetermined landing sites. In
case some problem occurred in this second phase, it would still be possible to put the spacecraft
back on a free-return using the propulsion system of the LEM, the Lunar Module, as a backup
to the propulsion system of the service module. An example of the effectiveness of this strategy
is the Apollo 13 accident. In that case, the loss of the command module occurred when the spacecraft
had already left the free-return trajectory, so the crew used the Lunar Module to return to it.
Actually, on that occasion the LEM engines were turned on also during the spontaneous return,
to shorten the return of 10 hours and to move the landing point from the Indian
Ocean to the Pacific, where most of the American help was concentrated.
In short, after more than fifty years things have not changed at all; the first Artemis
mission will see the Orion capsule reach the Moon using the same trajectories of that time.
With one difference... After having circumnavigated our satellite,
releasing at the same time the 13 Cubesat satellites, which represent the secondary
scientific payload, Orion will enter on a particular orbit, called Distant Retrograde Orbit.
This orbit, never used before, is extremely stable with respect to orbital perturbations because it
interacts with the Lagrangian points L1 and L2 of the Earth-Moon system, and it will be the
orbit that in the next missions will follow the Lunar Gateway, the Lunar Space Station,
which will be built starting from 2023. This station will support all Artemis missions starting
from Artemis 4 and will provide support for all future missions to the Moon and then to Mars.
The presence of the lunar station will allow to completely change the approach to landings
compared to the Apollo era. In the past, in fact, the spacecraft used by the Apollo astronauts
were able to carry a much greater amount of propellant than the Orion. This resulted in
a greater thrust provided by the engines that allowed, with the Lunar Orbit Insertion maneuver,
to reach a very low lunar orbit, from which to start directly the descent maneuvers.
The philosophy of the Artemis program will be instead to dock the Orion with the Gateway
on a much higher orbit and from there descend to the surface
with a dedicated vehicle (provided by SpaceX). The orbital variant will take Orion 60,000 km
away from the Moon. Thus beating the distance record achieved by Apollo 13 in 1970.
After six days, the Orion capsule will exit the Distant Retrograde Orbit with another lunar flyby,
finally pushing it back on course for home. After the usual three-day journey, near the Earth,
the spacecraft will shed its Service Module and dive into our planet's atmosphere traveling at
11 kilometers per second. The heat shield of the capsule, so far never tested,
will have to withstand temperatures of about 2,700 degrees Celsius.
After more than three weeks and a total distance covered over two million kilometers,
the mission will end with a landing off the coast of Baja, California.
Will everything go well? Of course, it will,
and from the moment Commander Moonikin Campos emerges safely from the capsule
we will begin to count the months until the launch of Artemis II,
the mission that will take men to circumnavigate the Moon for the first time since 1972.
A mission that reminds us very closely of the fantastic feat of Apollo 8 at Christmas 1968.
So yes, we are convinced... Everything will be fine.