Orbital Reentry: Theoretical Possibilities and Practical Challenges

Would it be possible for someone to exit the ISS, use a thruster to reenter the atmosphere, and safely parachute down?

It seems intuitive that if an astronaut jumps off from the International Space Station (ISS), they could continue drifting in outer space. However, the reality is quite different. The ISS orbits Earth at an incredibly high speed of over 17,500 mph (approximately 7.8 km/s). As a result, jumping off the ISS would mean drifting away, not falling back to Earth. The astronaut still has the same orbital velocity and would continue to move in the same orbit if they are not slowed down or pushed in a different direction.

The real challenge in reentering the atmosphere lies in slowing down from orbital velocity. The astronaut would need to decelerate from an orbital speed of around 7.8 km/s to a sub-sonic speed to allow for a safe parachuting landing. Failing to do so would result in the astronaut burning up in the atmosphere, similar to what happened to the space shuttle Columbia during its reentry in 2003.

Theoretical Solutions and Proposals

However, with the right equipment and technology, it is theoretically possible for an astronaut to safely reenter the atmosphere after jumping from the ISS. Historical efforts such as the MOOSE (Man Out Of Space Easiest) proposal by GE in the early 1960s offer insight into potential solutions.

GE developed the MOOSE proposal to address the scenario of astronauts being stranded in space. The MOOSE system comprised a suitcase-sized package containing a small rocket, a deorbiting parachute, and an "entry vehicle."

Step-by-Step Reentry Procedure

First, the astronaut would use the small rocket to orient themselves against the direction of the orbit.

Next, the rocket would fire, slowing the astronaut enough so that their orbit intersects the upper atmosphere.

The astronaut would then seal themselves into an astronaut-sized plastic bag with a cone-shaped flexible heat shield on one side.

Two pressurized bottles would fill the bag with expanding foam, sealing the astronaut inside.

During reentry, the astronaut would experience a butt-first descent, feeling everything but seeing nothing due to the lack of windows.

Automatically, the parachute would deploy when the astronaut reaches a sufficient altitude, and an emergency radio beacon would activate.

The landing could be in water or on land. The expanding foam would sufficiently cushion the landing to prevent injuries.

A handle could be pulled to activate several small explosive charges, breaking the bag into several large pieces, freeing the astronaut and exposing their equipment such as a radio, flares, first aid kit, food, and water.

While the MOOSE proposal seems exciting, this system was not adopted by the Air Force or NASA. The reasons for this could be related to technological, financial, and safety concerns. Nonetheless, the MOOSE system provides a glimpse into the complex and innovative solutions that could be developed to address the challenges of such a reentry scenario.

For more details on the MOOSE proposal, you can refer to these links:

It is important to remember that while the theoretical solution appears feasible, the practical challenges and risks involved make such a scenario highly unlikely for current space exploration efforts. The design and development of such systems require extensive testing, validation, and approval processes.

Comparing this idea to a high-altitude balloon jump (where the jumper is stationary) highlights the significant difference in altitude and velocity. In the case of the ISS, the astronaut's speed is the key factor that makes reentry a complex and hazardous process. Therefore, the altitude limit for such an option is primarily dictated by the need to decelerate from orbital velocity and achieve sub-sonic speeds for safe reentry.

Conclusion

In conclusion, while the idea of an astronaut exiting the ISS, using a thruster to reenter the atmosphere, and parachuting down is theoretically interesting, it presents significant challenges in terms of decelerating from orbital velocity. The MOOSE proposal by GE offers insight into potential solutions, but current space technology and protocols prioritize safety and feasibility over such theoretical scenarios.