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Estimation of Lunar Surface Shock
Effects and Optimization of Damping Scenarios: A Case Study in Response to
NASA's Request for Proposal
Abdi-Basid Ibrahim
ADAN*
* Correspondance : abdi-basid@outlook.com
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The aim of the present work is to
respond to NASA's request for proposals on understanding and reducing the
adverse effects of landing or take-off on the lunar surface. Two initiatives
can be developed. The first is that of a natural satellite with no atmospheric
layer, which suggests that any particle will fall at the same speed in the
absence of any air friction effects. A rocket could land without any major
impact. The second is to take into
account an atmosphere above the lunar surface. Terrestrial particles are likely
to form and remain in suspension for some time. To remedy this situation, six
scenarios were explored. Two alternatives have emerged from these investigations:
The first is the installation of a
device (rocket accessories) to reduce the effects of the fuselage during
ascent;
The second is the integration of new features into the rocket, such as vertical fuselages or a folding and unfolding locomotion slide to move the dust cloud away from the formation zone.
Keywords : NASA, Landing, Moon, Regolith, Lift-off, Artemis, Starship Virginia, Hampton, Human Lander
1.
Introduction
In space, granular and rocky materials are subject to both gravitational
and atmospheric circulation forces during a disturbance. The latter derives its
ancestral force from temperature, i.e. solar radiation [1]. Without the
existence of an atmospheric layer and the spherical shape, atmospheric
circulation modelling would certainly have taken a wrong turn. On the lunar
surface, the conditions of reasonable distance from the solar source (i.e.
150,000,000 km [2]) and sphericity can be an asset for comparison
with the Earth. In the absence of a layer of air enveloping its surface, the
equilibrium of a homogeneous spatial temperature distribution around a mean
value cannot be justified on the lunar surface (unlike Saturn's moon Titan).
The aim of this first work is to contribute to a philosophical
understanding of how granular and rocky materials of all sizes can behave on
the lunar surface after being exposed to the landing or take-off force of a
rocket weighing several thousand tonnes.
Until now, rocket take-off and landing missions have been carried out in
vertical motion and are assumed to have the same impact effect on surfaces,
even if the weight of the re-launch is slightly different from that of the
ascent, due to the variation in the weight of the on-board fuel.
The gravity field on the lunar surface is calculated at 1.62 m/s2
[3], i.e. a gravitational acceleration some six times lower than on the Earth's
surface (9.81 m/s2 [4]). An Artemis rocket with crew and cargo can
weigh at least 2,000 tonnes [5]. The amount of fuel and its weight are
astronomically proportional to the mission's round-trip distance, engine
efficiency and on-board engine technology.
For a landing mission, there is a threshold altitude at which a surface
covered in dust and rock is touched by the propulsion force (e.g. 39,144 kN [5]), which
keeps the weight of the craft suspended in the void and slows down gravitational
attraction. In principle, the slower the ascent, the greater the impact on the
surface. Contrary to what happens on Earth, the return to normal after an
ascent impact on the lunar surface for a landing mission would be faster with
the same time interval, whatever the characteristics of the seed and rock
lifted. For rocks thrown up with kinetic force, the impact does not seem to
affect the craft directly or indirectly. On the other hand, the stronger the
gravitational field, the faster the rocket's ascent is expected to be, so as
not to over-consume on-board fuel, while avoiding a hard landing that would
disable many of the craft's functions and features. Given the Earth's gravity
field, a lunar landing mission would be around six times slower and six times
more fuel-efficient.
In addition, thanks to the Lunar Atmosphere and Dust Environment Explorer
(LADEE) mission, recent studies [6,7] have changed our perception of the Moon,
confirming the presence of a lunar atmosphere, albeit almost negligible
compared with that of the Earth. The sources of this atmosphere can be
multiple: meteorite bombardment, rock decomposition, solar eruptions, etc.
When examining the lunar atmospheric layer, it will be vitally important
to understand the atmospheric pressure with the elements that make up the lunar
atmosphere, mainly argon, helium, sodium and hydrogen. The shock effect on the
lunar surface would be based essentially on the interaction potentials of these
latter chemical elements.
With a view to providing some answers to NASA's project, the remainder of
this article is organized as follows:
- First, we analyze an approach in which cloud cover is neglected.
- Secondly, we counter this approach by proposing scenarios and draft
solutions.
2.
Analysis of the Artemis landing mission:
case without lunar atmosphere
The riskiest incident on a lunar mission would not be the suspension of
rocks and other particles in lunar space, since all rocks, whatever their size,
would fall at the same speed. In addition, the spiral effect observed in the
drag of turbojet aircraft would not exist on the Moon, due to the absence of
air particles. What's more, the projections caused by the blast effect on
landing will be projected in all directions, from the source of the ascent to
extremities whose distance is proportional to the force. In this context, the
risks of a mission to the Moon are much lower than on Earth. Impact with the
surface does not directly or indirectly endanger the spacecraft, except in the
case of nearby installations.
Prospecting the lunar surface and its stiffness composition would appear
to be an indispensable asset in the study of an initial landing strip.
Meteorite impact zones can represent a major hazard for rocket landings and
take-offs. Projections of elements from the lunar surface can cause fallout on
the rocket, due to its specific funnel shape at the point of impact with the
lunar surface. The geological characteristics of the more rigid zones should be
compared between the Moon's surface and that of the Earth, in order to identify
an optimum zone for reducing the impact of rocket engine propulsion.
3.
Analysis of the Artemis landing mission:
case with lunar atmosphere
In this section, we analyze five scenarios whose feasibility seems to be
approaching with the maturity of current technologies. This section takes into
account the importance of the lunar atmosphere and proposes solutions to avoid
complications with the dust cloud during ascent.
3.1.
Scenario 1 : absorption
In the scenario shown in figure 1, at a precise and optimal altitude during
ascent, the rocket detaches a circular capsule (which can be unfolded and
folded), absorbing the propelled granular and rocky materials and releasing the
absorbed air by filtering. This device is designed to withstand the extreme
temperature of the fuselage, and to incorporate artificial intelligence to
identify rocks according to their respective risks. The prototype shown in
figure 1 is
essentially based on the capacity and performance of rock and dust aspirators,
which will be released at a given altitude before landing. The parameters of
these aspirators will be designed to ensure a safe landing of Artemis on the
lunar surface.
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Figure 1. Circular vacuum cleaner for dust and granules.
3.2.
Scenario 2 : parachuting
The scenario described in figure 2 involves parachutes being released to
trap granular and rocky material rising towards the summit during ascent. The number of parachutes used may vary to
optimize landing safety. The characteristics of these parachutes must
correspond to the results expected for the safety mission. In addition, each
parachute must be equipped with a device that detects and predicts the area
most affected by the fuselage explosion, in order to optimize deployment on the
priority area. This requires the use of artificial intelligence. The
feasibility of such a device seems certain to reduce rock and granule heave, as
well as the formation of dust clouds.
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Figure 2. Case of a parachute trapping the effects of shock.
3.3.
Scenario 3 : artificial vat
The scenario in figure 3 describes a prototype that deploys a device
capable of sinking into the lunar soil (like a tomahawk missile) and deploying
a kind of metal tank inside the soil. The latter is adapted to the overheated
condition and will contain the blast, while sparing the lunar soil from being
impacted by the blast.
This will prevent the formation of dust clouds and reduce the risk of
dust impacting the rocket engine during landing [8].
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Figure 3. Case of a tank sinking to the surface of the moon.
3.4.
Scenario 4 : surface copper
In the scenario below (figure 4), as the rocket ascends, at a precise and ideal
altitude, a slide ejects from the rocket and deploys over a wide lunar surface
to serve as a landing point and avoid the lifting of granules and other rocky
material. Unlike the previous scenario, this is a surface deployment with
automatic ground engagement. This shows just how important automatic devices
and artificial intelligence are for this mission.
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Figure 4. Cas de cuivre dépliable comme point d’atterrissage.
3.5.
Scenario 5 : fuselage horizontal
In the scenario shown in Figure 5, the rocket fuselage would have to be redesigned
to incorporate a new vertical fuselage system capable of slowing down gravity.
Self-deploying vertical fuselages are intended to compensate for the
traditional fuselage. This approach will minimize the blast effect of the
fuselage on the lunar surface.
Other modifications can also be made, including the integration of a
wheel to help the rocket move away from the dust cloud formation zone after
landing.
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Figure 5. Feasibility scenario of additional fuselage rotation during Artemis landing.
3.6.
Scenario 6 : dust cover
In the final scenario of the Artemis mission back to the moon, the ship's
skin should have physico-chemical properties that prevent dust from clinging to
the ship. This proposal, presented in figure 6, can be based on the secret of dust adhering to
materials, allowing the rocket to remain free of dust and rocks, while landing
safely. In addition, it is possible to develop a device that propels small
quantities of water to wet the dust and limit its effects.
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Figure 6. Feasibility case for a dust cover on the Artemis surface.
4. Relationship between distance, weight, projection
effects and landing time
In this subsection, we set up an empirical
program to model the impact phenomenon on a surface covered with dust and rock
:
We consider the variables :
Ø T, existence of atmospheric
circulation
Ø U, the surface area of the
impact zone
Ø V, rocket landing time.
Ø W, shock absorption time.
Ø X, rocket weight;
Ø Y, local gravity field;
Ø Z, kinetic force of the
projected lunar rock fragment.
Based on this program, the following hypotheses
can be formulated:
1. The surface area of the
impact zone increases with the weight of the rocket.
2. The existence of atmospheric
circulation contributes to a major risk during ascent.
3. Landing time contributes to rocket blast
impact area.
4. Time to return to normal
after landing depends on gravity and the existence of an atmosphere.
5. The weight of the rocket is
positively correlated with the level of risk of danger from surface impact
effects.
To minimize the risk of clouds of dust and rocky
material forming during the ascent of Artemis, this would require simulations
based on mathematical formulations that describe the relationships between the
variables defined above. In addition, observations of each of these variables
can be used to develop a simpler model with a study of multidimensional
variation.
Conclusion
On the lunar surface, a
rocket will weigh 6 times less than on Earth. Rock fragments and the formation
of lunar dust clouds can be mitigated by studying the physical properties of
the chemical particles that make up the lunar atmosphere. The disturbance of
lunar surface materials during rocket ascent is due not only to the gravity
field, but also to the atmosphere, whose density is almost negligible for the
moon.
Landing with the least
possible effect will require the invention of new prototypes incorporating
artificial intelligence to maximize decision-making in the shortest possible
time. Fuselage modifications and the integration of new rocket functionalities
will also be required.
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