The question of how long it takes to travel to the Sun is far more complex than simply calculating the distance and dividing it by a spacecraft’s speed. Our star is approximately 93 million miles away, yet reaching it is one of the most energetically challenging journeys in the solar system. The true difficulty lies not in the distance, but in the physics required to counteract Earth’s orbital speed. Any mission attempting this feat must first overcome the momentum that keeps our planet in a stable, elliptical path around the Sun. This requirement is why solar missions take years to complete their journey.
Addressing the Velocity Problem
To understand solar travel, consider the motion of our own planet. Earth is not stationary in space but is orbiting the Sun at an average velocity of roughly 67,000 miles per hour. This rapid sideways movement, or orbital velocity, is what prevents Earth from falling directly into the Sun’s gravitational pull.
A spacecraft launched from Earth has this same orbital speed, meaning it is already moving extremely fast in a direction tangential to the Sun. To send a probe toward the Sun, engineers must design a trajectory that dramatically reduces this sideways momentum. The problem is not one of speed, but of deceleration relative to the Sun’s center.
If a spacecraft were to completely cancel out Earth’s entire orbital velocity, it would require a large expenditure of energy, known as delta-V, equivalent to about 21 to 26 kilometers per second of change in speed. This level of deceleration is currently impossible for a single rocket burn using existing chemical propulsion technology. Instead of accelerating away from the Sun, as is done for missions to the outer solar system, a solar mission must apply a braking force to allow the Sun’s gravity to finally pull the probe inward.
The Actual Journey Time
Because a direct, high-speed braking maneuver is unfeasible, solar missions must rely on an energy-saving technique. This method involves using gravity assists, also known as slingshot maneuvers, from other planets to gradually reduce the spacecraft’s orbital speed around the Sun. This process extends the travel time but makes the mission possible with current technology.
The Parker Solar Probe, for example, launched in 2018, was designed to make its final, closest approach to the Sun’s atmosphere in late 2024. This seven-year journey requires seven separate flybys of the planet Venus. Each pass uses Venus’s gravity to slow the probe down and tighten its orbit around the Sun, incrementally shedding the necessary orbital energy.
Earlier missions, such as the Helios 1 and Helios 2 probes launched in the 1970s, took a more direct, but still lengthy, path to the Sun’s vicinity. Helios 1, launched in December 1974, reached its closest distance to the Sun in March 1975, a journey of just over three months. However, these probes only traveled to about 28 million miles from the Sun, which is still well outside the orbit of Mercury.
The time for a solar journey varies widely based on the mission’s ultimate goal and the trajectory chosen. A mission aiming for a close flyby, just inside Mercury’s orbit, might take a few months, as demonstrated by the Helios probes. However, a mission like the Parker Solar Probe, which is designed to repeatedly graze the Sun’s corona at a distance of only a few million miles, requires a seven-year, multi-flyby strategy to achieve its final, extreme orbit.
Comparative Scale of Solar Travel
Placing the Sun journey in context reveals its unique difficulty compared to other space travel milestones. A trip to the Moon is measured in days, taking only three days for a transit. Even a journey to Mars, which is physically farther away than the Sun, is measured in months, usually taking about six to nine months depending on the orbital alignment.
The time difference highlights that traveling to the Sun is not a distance problem, but an energy problem. While Mars is millions of miles farther from Earth than the Sun is in the other direction, a spacecraft traveling to Mars is adding to Earth’s orbital velocity to escape the Sun’s pull, a simpler maneuver. By contrast, traveling to the Sun requires the energy expenditure of braking against Earth’s momentum, which forces engineers to adopt the multi-year, gravity-assist approach.