Rhea-Colossus 4

Photo of Earth taken by Sharpe during his flight

**Rhea-Colossus 4** was the first crewed American spaceflight, which took place on January 14th 1962. Piloted by astronaut Garry Sharpe and operated by NASA as a part of Project Rhea, it was the third manned spaceflight, preceded by Soviet orbital flights Vostok 1 and 2.

Rhea spacecraft #12 was carried into orbit by an HGM-36B Colossus launch vehicle lifting off from Launch Complex 19 at Cape Canaveral, Florida. After two orbits, the spacecraft reentered the Earth's atmosphere and splashed down in the Pacific Ocean just 128 kilometers from Hawaii. Total flight time was two hours 36 minutes and 43 seconds.

## Preparation

The spacecraft Rhea capsule #12 was delivered to Cape Canaveral in August of 1961. It was originally slated to fly a final orbital test mission, but after the flight of Vostok 2 the Rhea-Colossus 4 mission was re-designated as the first crewed flight of Project Rhea. Spacecraft 12 went through extensive development and testing work before it was deemed safe for flight, this pushed the launch date back from December of 1961 to mid-January of 1962.

Astronaut Garry Sharpe was selected to fly the first orbital mission, with Ian March as his backup. As the effects of orbital spaceflight were unknown except to the Soviets, Sharpe was prepared with an orbital medical kit containing several painkillers and medicine to treat shock symptoms. He was also provided with a survival kit in the event the spacecraft landed off course.

Cameras were placed on both the interior and exterior of the capsule to monitor the astronaut, and to take photos of Earth from orbit.

## Flight

### Launch

Sharpe boarded the spacecraft early in the morning on January 14th. The hatch was bolted shut with a series of explosive bolts that would blow the hatch off following splashdown. Two hours after entering the spacecraft the Colossus rocket ignited it's engine and lifted off from Launch Complex 19.

As Colossus and Rhea passed through max Q vibration on the rocket passed expected levels, but after passing max Q the flight smoothed out. At three minutes and two seconds, the main engine shut down on time and the second stage was separated. Three seconds later the second stage engine ignited right on schedule. The launch escape tower was jettisoned at an altitude of 75 kilometers and the spacecraft pitched over further, giving Sharpe his first view of the horizon.

At nine minutes after liftoff the second stage engine shut off and the spacecraft was in orbit. Sharpe received word that the trajectory was good for at least six orbits.

### First Orbit

The Rhea spacecraft successfully separated from the Colossus second stage, Sharpe attempted to flip the spacecraft around to image the second stage but a temporary error in the reaction control thrusters prevented this from happening. The capsule aborted the maneuver and the altitude control system was activated to place the spacecraft into a nominal orbital altitude. Once this maneuver was complete Rhea-Colossus 4 began its first orbit.

When Rhea passed over the Atlantic ocean mission controllers reported that all spacecraft systems were functioning perfectly. Sharpe took this time to take several photos of the Earth these being some of the first color images of the Earth captured from space. As the spacecraft passed over the African coastline Sharpe was informed that he was go for a second orbit.

### Second Orbit

As the second orbit began Sharpe performed a number of tests with the Mariner Relay network, further verifying the value of orbital tracking technology. Tracking ships positioned along Rhea's orbital path launched a series of highly reflective balloons for Sharpe to observe as he passed over them. Sharpe was unable to locate the balloons do to the small size of the spacecraft's porthole but did make observations of lightning strikes occurring near one of the tracking ships.

### Reentry and Splashdown

Rhea passed over the Indian Ocean nearing the end of its second orbit, Sharpe was given the go for retro rocket fire. The first retro rocket fired successfully with the other two firing simultaneously two seconds later. The retro burn lasted about 15 seconds and placed the capsule on a trajectory that would lead to it landing near the Hawaiian islands.

12 minutes prior to reentry Sharpe flipped the switch that would jettison the retro pack only one of the two straps that held the retro pack in place causing the package to hang freely from the side of the spacecraft. When reentry began the retro package collided with the heat shield pressing against it, the spacecraft began to tumble due to the uneven center of mass. The tumble caused a spike in temperature inside the capsule, post flight analysis showed that temperatures reached a peak of 49° C (120.2° F). The aerodynamic forces, and the heating of reentry acted to break the strap releasing the retro pack. The capsule's RCS thrusters maneuvered the spacecraft into a safe reentry angle.

The recovery ship spotted the spacecraft during reentry and were the first to report the nominal deployment of the drogue parachute. At an altitude of 1581 kilometers the drogue chute was cut and the main parachute deployed successfully. The landing bag deployed a few seconds later. The spacecraft splashed down in the Pacific Ocean about 170 kilometers away from the planned landing zone.

The hot temperatures inside the spacecraft led to Sharpe blowing the hatch off of the capsule this caused water to start flowing into the spacecraft Sharpe deployed a small life raft from within his survival kit and fired a flare to signal the nearby rescue ships. The spacecraft sunk to the ocean floor and was never recovered.