Seven smartphone experiments to understand space travel

Jessica Meir has been floating in the ISS since 14 February 2026. Artemis II just brought back four astronauts from a historic flyby of the Moon on 10 April. Space exploration has never been more present in the news, and the questions it raises (how do you stay in orbit? why do you float in space? how do you slow down to land on the Moon?) are at the heart of middle school and high school physics curricula. In this article, we propose seven experiments that can be performed with a smartphone, a tablet or a computer, allowing students to understand the physics of space travel. They will take us into orbit around Earth, into the heart of a centrifuge, onto the Moon and even to the edge of the solar system. Are you ready?

Table of contents:

Space in the classroom — Preparing for the journey — Floating in space — Landing a rocket — Putting a satellite in orbit — Kepler's laws and the solar system — Translunar injection — The gravitational slingshot — Conclusion and bibliography

Space in the classroom

The year 2026 is an exceptional one for global spaceflight. On 13 February, NASA astronaut Jessica Meir lifted off from Cape Canaveral as commander of the SpaceX Crew Dragon capsule heading to the International Space Station, leading the international Crew-12 mission for about eight months. A marine biologist by training — her doctoral research studied how emperor penguins and bar-headed geese cope with extreme low-oxygen environments — Meir is making her second trip to space. Her first, in 2019-2020, lasted 204 days, during which she made history by performing the first all-female spacewalk alongside fellow NASA astronaut Christina Koch. Remarkably, Koch is now part of the Artemis II crew that just flew around the Moon — the first woman ever to travel beyond low Earth orbit. On board the ISS, the Crew-12 astronauts are taking part in more than 200 scientific experiments, covering human physiology, materials research and preparation for future lunar exploration.

A few weeks later, on 1 April 2026, NASA launched Artemis II, the first crewed mission to the Moon since Apollo 17 in 1972. Four astronauts (Reid Wiseman, Victor Glover, Christina Koch and Canadian Jeremy Hansen) flew over the far side of the Moon aboard the Orion spacecraft, propelled by the super-heavy SLS launcher. After a ten-day journey covering more than 1.1 million kilometres, the crew splashed down on 10 April off the coast of San Diego. The continuation of the programme is already mapped out: Artemis III in 2027 will test orbital rendezvous with commercial landers, before Artemis IV brings astronauts back to the lunar surface in 2028.

How can we capitalize on this enthusiasm to do physics in the classroom? The physical phenomena that govern space travel — gravitation, centripetal acceleration, orbital mechanics — are in fact within reach of experimentation. Everyone has a real physics laboratory in their pocket: a smartphone, equipped with accelerometers, gyroscopes and magnetometers. Free apps such as FizziQ, Phyphox or Physics Toolbox provide easy access to these sensors, allowing data to be recorded and analysed graphically. For video motion analysis, tools like FizziQ's Kinematics module or Tracker make it possible to break down the motion of an object frame by frame. Finally, for orbital mechanics, online simulators such as the FizziQ Web Orbits and Gravitation module [1] make it possible to model the trajectories of planets and satellites directly in a browser.

In the seven experiments that follow, we will use in turn the smartphone's sensors, video analysis and numerical simulation. This pathway forms a logical progression that follows the stages of a space trip: weightlessness and astronaut training, takeoff and rocket return, then the orbital mechanics that allow you to navigate space.

1. Preparing for the journey

Theme: Centripetal acceleration and g-forces | Level: Grade 9 – High school | Sensor: Accelerometer | Duration: 30 min

Before floating in the ISS, Jessica Meir had to withstand the considerable forces of liftoff. During the Falcon 9 launch on 13 February, she experienced up to 3 to 4 g — meaning her body weighed three to four times its normal weight. For the Artemis II astronauts, propelled by the enormous SLS and its two solid boosters, conditions were even more intense. How does the human body cope with such forces?

Astronauts train in centrifuges. Like all NASA astronauts, Jessica Meir spent hours in centrifuges and parabolic-flight aircraft during her training at Johnson Space Center, experiencing forces several times Earth's gravity. In class, you can understand these effects very simply: just hold a smartphone at arm's length and spin around while recording the acceleration. This accessible experiment already allows you to observe how acceleration increases with rotation speed, and to introduce the laws of uniform circular motion.

To go further and measure with greater precision, you can use an unexpected tool: a salad spinner. Place the smartphone in the basket and record absolute acceleration while turning the crank at different speeds. You can then experimentally verify the relation a = ω²·R, which links centripetal acceleration to angular velocity and rotation radius.

In a typical salad spinner, the radius is about 10 cm. A vigorous rotation gives an angular velocity of about 10 rad/s, i.e. a centripetal acceleration of about 10 m/s², barely 1 g. To reach the 3 g of a Falcon 9 liftoff, you would have to spin 1.7 times faster. For the 8 g of a military training centrifuge, almost 3 times faster. A human can briefly withstand about 9 g before losing consciousness. Beyond that, blood can no longer reach the brain and vision becomes blurred ("grey-out" then "black-out").

This activity can be supplemented by the FizziQ Web Centrifuge numerical simulation, which allows the g-factor to be visualized for configurations inaccessible in the classroom: large radii, high rotation speeds, and the connection with the artificial gravity envisaged for future flights to Mars.

➡️ Activities: Astronaut and wringer and In orbit | Simulation: Centrifuge

2. Floating in space

Theme: Weightlessness and free fall | Level: Grade 9 – High school | Sensor: Accelerometer | Duration: 30 min

Since 14 February, Jessica Meir has been living in weightlessness in the ISS, alongside her three Crew-12 colleagues. Among them is ESA astronaut Sophie Adenot — only the second French woman ever to fly to space, twenty-five years after Claudie Haigneré aboard the Mir station. A former helicopter test pilot and colonel in the French Air and Space Force, Adenot is leading the European "Epsilon" mission, taking part in seven dedicated experiments developed by the French space agency CNES on astronaut health monitoring and bone density. Together with Meir, Koch on Artemis II, and the growing number of women selected by NASA and ESA, she illustrates how human spaceflight has become genuinely international and increasingly mixed.

Images of life on board show the crew floating in the station's modules, handling instruments that seem to defy gravity. But why are they floating? Is it because there is no gravity in space? The counter-intuitive answer is that gravity at ISS altitude (about 400 km) is still 8.7 m/s², or 89% of its value at ground level. The astronauts float because the station and everything in it are in permanent free fall around Earth.

To understand this phenomenon, there is no need to go to space. All you need is a smartphone and an app that can read the accelerometer (FizziQ, Phyphox, Physics Toolbox…). Place the smartphone on a table and open the absolute-acceleration measurement instrument. The displayed value is about 9.80 m/s². The smartphone is at rest, but the accelerometer detects the table's reaction force opposing gravity. If you change the phone's orientation, the value remains constant: it is the magnitude of the gravitational vector.

Now place a thick mattress on the floor, start recording and toss the smartphone in a small parabola so it lands gently on the mattress (30 to 50 cm is enough — mind the breakage!). Analysing the recording, you find that throughout the airborne phase the measured acceleration is zero. The graph shows three distinct phases: the throw (acceleration greater than g, the hand pushes the phone), free flight (acceleration close to zero) and the impact on the mattress (acceleration peak). The duration of the weightlessness phase can be measured: for a 50 cm toss, it is about 0.64 seconds, in agreement with the formula t = 2√(2h/g). In a Zero G aircraft used for astronaut training, the parabola lasts about 22 seconds.

Weightlessness is therefore not the absence of gravity — it is the absence of a reaction force. This result illustrates Einstein's equivalence principle: inside a closed system, it is impossible to distinguish free fall from the absence of gravity. This idea, formulated in 1907, would lead Einstein to the theory of general relativity. To go deeper into the topic, see our article on seven experiments on gravity [2].

➡️ Activity: Parabolic flight

3. Landing a rocket

Theme: Video kinematic analysis | Level: Grade 9 – High school | Tool: Video analysis | Duration: 45 min

Jessica Meir and the Crew-12 astronauts reached the ISS aboard a Crew Dragon capsule, launched by a SpaceX Falcon 9 rocket. One of SpaceX's feats is the recovery of the first stage, which lands vertically on a barge at sea. How is this spectacular landing piloted? Is the descent uniform, accelerated, or does it follow another profile?

To answer, we use video motion analysis, a powerful technique available in apps like FizziQ (Kinematics module), Tracker or Vernier Video Physics. Starting from a video of a Falcon 9 landing (many examples are available on YouTube or in the FizziQ video library), you point the rocket's position frame by frame to reconstruct its trajectory and speed profile.

The analysis reveals that the rocket's descent speed decreases linearly with time, which corresponds to constant deceleration. This is no accident: a constant-deceleration braking profile is optimal in terms of fuel consumption. The rocket fires its engine at the last moment and brakes just enough to reach zero speed exactly at touchdown. This kind of manoeuvre, called a "suicide burn" or "hoverslam" in space jargon, is a calculated trade-off between efficiency and safety.

This analysis opens a discussion on the challenges of the lunar landing planned for future Artemis missions. On the Moon, the absence of an atmosphere makes any aerodynamic braking impossible: all deceleration must be supplied by the engines. In addition, lunar gravity (1.6 m/s²) changes the parameters of the problem. Students can ask themselves: with gravity six times weaker, do you need more or less fuel to land? The answer is not trivial, because while the weight is lower, the mass to brake remains the same.

➡️ Activity: Space X rocket

4. Putting a satellite in orbit

Theme: Geostationary orbit and Kepler's laws | Level: Grade 9 – High school | Tool: Numerical simulation | Duration:30 min

The ISS in which Jessica Meir lives is a satellite: it orbits Earth at about 400 km altitude, completing one full revolution in only 90 minutes. That means Meir sees the sun rise and set 16 times a day! Weather satellites, on the other hand, are placed in geostationary orbit at 36,000 km altitude, where their period is exactly 24 hours: they appear motionless as seen from the ground.

Why this difference? How does distance from Earth determine a satellite's speed and period? In the Orbits and Gravitation simulator, students must place a satellite in geostationary orbit. They discover there is only one altitude at which a satellite has a 24-hour period: too low, it orbits too fast; too high, too slowly. This is a direct application of the relation v = √(G·M/r) and Kepler's third law.

A surprising result then emerges: the higher the satellite, the slower it goes. Meir's ISS races at 7.7 km/s to stay in low orbit, while a geostationary satellite moves at only 3.1 km/s. Orbital speed is not a question of launcher power but a consequence of the law of universal gravitation.

By recording data from the simulation, students can quantitatively verify Kepler's law by plotting T² versus r³ for different orbital altitudes. The points line up perfectly, confirming the proportionality. The mass of Earth can then be extracted from the slope of the graph — a beautiful indirect measurement made purely from celestial mechanics.

➡️ Activities: Weather satellite, Lunar period

5. Kepler's laws and the solar system

Theme: Celestial mechanics | Level: High school | Tool: Numerical simulation | Duration: 45 min

Kepler's laws, formulated at the beginning of the 17th century from Tycho Brahe's observations, are the foundation of all modern space navigation. They make it possible to compute the trajectories of probes, spacecraft and planets. The Artemis mission uses these same laws, discovered more than four centuries ago, to send astronauts to the Moon.

In this activity, students model the inner solar system in the Orbits and Gravitation simulator: the Sun at the centre, then Mercury, Venus, Earth and Mars, each with its real mass, real distance and orbital speed. The distance scale is set to about 1,000,000 km/pixel and the time step to several hours per frame to observe revolutions. Once the simulation is launched, the four planets can be seen orbiting the Sun at very different speeds.

The verification of Kepler's third law (T² / a³ = constant) is well suited to this simulation. By recording each planet's period and orbital radius in the experiment notebook, students build a table and verify that the T²/a³ ratio is indeed the same for all planets. They can also observe Kepler's first law (orbits are ellipses) by giving an initial speed slightly different from the circular speed.

The notion of Hohmann transfer can also be introduced — the most economical orbital manoeuvre for moving from one orbit to another. This is the principle used by space missions to leave Earth's orbit and head for the Moon or Mars. By giving an impulse (a sudden increase in speed) to a body in circular orbit, you can observe how its trajectory deforms into an ellipse that may intercept a higher orbit.

➡️ Activity: Solar system

6. Translunar injection

Theme: Earth-Moon trajectory and free return | Level: High school | Tool: Numerical simulation | Duration: 45 min

We can go further and try to reproduce, in simplified form, the Artemis II mission. In space-mission language, translunar injection (TLI) is the impulse that takes a spacecraft from an Earth orbit to a trajectory heading for the Moon. During Artemis II, it was the European Service Module (ESM) engine that performed this manoeuvre on 2 April 2026, firing for about six minutes.

To model this situation in the Orbits and Gravitation simulator, we adopt a simplified protocol: place Earth at the centre with zero velocity, and the Moon at 384,400 km, also at zero velocity. The Moon does not orbit Earth, which simplifies the problem and lets us focus on the spacecraft's trajectory. We then add a third body of negligible mass (a space probe) at 36,000 km from Earth — i.e. at geostationary-orbit distance — and give it an initial velocity directed towards the Moon.

The question is simple: what speed must this probe be given so that it reaches the Moon, swings behind it, and returns towards Earth?

It is a real experimental challenge, to be solved by trial and error. If the starting speed is too low, the probe falls back towards Earth without reaching the Moon. Too high, it overshoots the Moon and escapes the system. The launch direction must also be adjusted. Through successive trials, students discover that there exists a narrow speed window allowing the probe to swing around the Moon and return naturally to Earth, without any trajectory correction.

This is the principle of the "free return trajectory" used by Artemis II, and before it by the Apollo missions. If the spacecraft's engines fail after translunar injection, the Moon's gravity deflects the trajectory and sends the spacecraft back towards Earth. This is what saved the Apollo 13 crew in 1970.

By manipulating the simulator, students concretely understand why this trajectory exists and how strongly it depends on the precision of the initial speed.

➡️ Activity: Translunar injection

7. The gravitational slingshot

Theme: Gravity assist | Level: High school – Higher education | Tool: Numerical simulation | Duration: 45 min

To conclude our journey, let's move further from Earth and the Moon to explore gravity assist, also called the "gravitational slingshot". This manoeuvre allows a probe to gain speed by flying past a planet, without burning fuel. It is thanks to this technique that the Voyager probes were able to reach the edge of the solar system, and that the Cassini probe was able to reach Saturn.

In the simulator, students configure a scenario where a massive planet (Saturn, for example) is moving, and a space probe passes nearby. By measuring the probe's speed before and after the flyby (using the data exported to the experiment notebook), you find that the probe exits the flyby with a higher speed than its entry speed.

How is this possible without violating energy conservation? The key is that the planet is moving. From the planet's point of view, the probe enters and exits at the same speed — it is a simple problem of symmetric deflection. But from the Sun's point of view (the reference frame in which we navigate), the probe has "borrowed" a tiny amount of kinetic energy from the planet. Saturn is so massive that its loss of speed is unmeasurable, but the probe, much lighter, gains a significant amount of speed. It is a bit like a tennis ball bouncing off a moving truck: it leaves much faster than it arrived.

This technique could be used in future deep-exploration missions. Even for the Artemis missions, understanding three-body gravitational interactions (Earth-Moon-spacecraft) is essential to optimize trajectories and save fuel. The complementary activity Three-body problem lets you explore the deterministic chaos that arises when three masses interact — a phenomenon that makes space navigation as complex as it is fascinating.

➡️ Activity: Gravitational slingshot

Conclusion

We have presented seven experiments covering a broad spectrum of the physics of space travel, from the bodily sensations of the astronaut to celestial mechanics. Their thread follows the stages of a space mission: understanding the weightlessness Jessica Meir and Sophie Adenot experience in the ISS (experiment 1), withstanding liftoff forces (2), mastering rocket landings (3), understanding satellite orbits (4), simulating a translunar injection like Artemis II's (5), navigating the solar system through Kepler's laws (6), and using planetary gravity as a free engine (7).

These activities can be carried out individually or combined into an interdisciplinary project around the Crew-12 mission and the Artemis programme. They draw on a variety of skills (measurement, modelling, graph analysis, critical thinking) and rely on accessible digital tools: the smartphone sensors that students have in their pocket, and free simulators usable from any browser.

The year 2026 is an opportunity to bring physics to life. When Jessica Meir performs an experiment in weightlessness aboard the ISS, or when Christina Koch and her crewmates gaze at the far side of the Moon from the Artemis II Orion capsule, the same Newton and Kepler laws govern their journey. The same laws that can be explored, measured and verified in the classroom, with a smartphone and a bit of curiosity.

References and bibliography

[1] FizziQ Web Orbits and Gravitation simulation documentation: complete user guide for the simulator, physical model, recommended configurations and educational activities. https://www.fizziq.org/post/documentation-simulation-orbites-gravitation (in French)

[2] "Seven Experiments on Gravity with your Smartphone": FizziQ blog article presenting experiments on gravity, free fall, the pendulum and the variation of g with altitude and latitude. https://www.fizziq.org/en/post/seven-experiments-on-gravity-part1

[3] NASA Crew-12 mission: official NASA page on the Crew-12 mission commanded by Jessica Meir, with crew biographies, launch details and mission objectives. https://www.nasa.gov/mission/spacex-crew-12/

[4] Artemis II: official NASA page describing the flight plan, crew and scientific objectives of the first crewed mission to the Moon since 1972. https://www.nasa.gov/mission/artemis-ii/

[5] "Artémis II : tout savoir avant le décollage": Cité de l'espace article detailing the mission's progress, flight phases and lunar trajectory profile. https://www.cite-espace.com/actualites-spatiales/tout-savoir-sur-la-mission-artemis-ii-avant-le-decollage/ (in French)

[6] Apollo 14 Pendulum Experiment: NASA archives documenting the accidental oscillation of a container on the Moon, which made it possible to verify the pendulum formula in lunar gravity. https://history.nasa.gov/alsj/a14/a14pendulum.html

[7] "Le pendule, la pesanteur et la latitude": Planet-Terre (ENS Lyon) resource on variations in Earth's gravity and their historical link with the pendulum. https://planet-terre.ens-lyon.fr/ressource/pendule-pesanteur-latitude.xml (in French)

[8] Phyphox: free app developed by RWTH Aachen University to use smartphone sensors in physics. https://phyphox.org

Keywords: Artemis, Jessica Meir, Sophie Adenot, ISS, Crew-12, gravitation, orbit, Kepler, acceleration, weightlessness, free fall, SpaceX, simulation