This week in space history is a bit special. Not only am I recording this from Pamela’s studio instead of my own monitor fort, but this week is a two-for-one topic. We’re going to talk about both the mission of Venera 4 and the first supersonic flight.

As its name suggests, Venera 4 was the fourth officially-named mission the Soviets sent toward Venus. However, it was the eighth attempt overall, as several other Venera-type missions failed to either reach or leave Earth orbit and were given a cover designation other than Venera.

Venera 1 through 3 made it out of Earth orbit, but contact was lost for various reasons. The first two missed Venus, while Venera 3 hit the planet two weeks after its transmitter failed.

Venera 4 had to succeed in sending back data from Venus.

Although the design was similar to previous missions, responsibility for making the probe was given to a different Soviet design bureau than the previous three. The biggest change was more rigorous ground testing of the spacecraft before launch to ensure it worked as intended.

And work it did. Venera 4 was launched on June 12, 1967, and arrived at Venus in October of the same year. The entry probe entered the atmosphere of Venus at 04:34 UTC on October 18. It hit the top of the atmosphere at 11 kilometers a second, reaching a peak deceleration of 300 gees.

It started sending back data after parachute deployment, and what it reported shocked scientists. From Mariner 2’s distant flyby, scientists knew Venus was really hot, at least 260 degrees Celsius, but Venera 4 measured a value from inside the atmosphere that varied from 33 to 262 degrees Celsius, depending on altitude.

What the flyby of Mariner 2 couldn’t determine was the pressure of Venus. Scientists didn’t know what it could be, so the instrument was only designed to measure up to 7.3 bars. This was maxed out quickly, and the actual value inferred from other data was over 75 bars of pressure. For reference, one bar is normal Earth pressure at sea level.

Other discoveries Venera 4 made included expanding knowledge about the composition of Venus’ atmosphere and the planet’s magnetic field. Before the mission, it was thought that the atmosphere was mostly nitrogen, but data sent back from Venera 4 indicated that Venus’ atmosphere was actually over 90% carbon dioxide and that the tops of the thick clouds obscuring the surface were at around 52 kilometers about the surface and extended down to 35 kilometers above the surface. It also confirmed that the planet has a weak magnetic field.

Venera 4 got further than its predecessors but unfortunately, didn’t make it to the surface as planned. The high pressure and temperature crushed and melted the spacecraft at an approximate altitude of 28 kilometers above the surface.

In all, Venera 4 transmitted for 93 minutes in the atmosphere of Venus, but it was not equipped with a camera. Based on the results of Venera 4, Venera 5 and 6 were designed to simply collect data from the atmosphere. The first successful landing on the surface of Venus was achieved by Venera 7 in December 1970.

Moving on: the first supersonic flight of the Bell X1.

After World War II, the next major challenge in aircraft design was flying faster than the speed of sound.

Starting right after the war, the U.S. Navy, along with NACA, the predecessor to NASA, and the U.S. Air Force started the development of a new experimental plane. It would attempt to solve control problems of flying at around and above supersonic speed. The design was simple: it used the same shape as a .50 caliber bullet, which was known to be stable at supersonic speeds.

The first X1 was finished in late 1945, and its first powered flight was a year later on December 9, 1946.

The rest of the test program was split between the Air Force and NACA. The Air Force would attempt to break Mach 1 as soon as possible, while NACA would take a more studied approach and conduct test flights to study the conditions just below the sound barrier.

The USAF’s riskier approach was uncomfortable to the NACA engineers, but they pressed on. Only six weeks after the change in test programs, the now famous pilot Chuck Yeager flew the USAF’s X1 to Mach 1.06 on October 14, 1947. That X1, which was the first one built, was used several more times before being retired in May 1950. Following retirement, it was donated to the Smithsonian Museum. It is currently on display in the Milestones of Flight Gallery in the National Air and Space Museum in Washington, D.C.

Breaking the sound barrier sounds like a major achievement that would be a major propaganda boost in the Cold War, but did the U.S. make a deal about it at the time? No. Instead, the flight was classified and only revealed publicly in March 1948.

A NACA pilot, Herbert Hoover (unrelated to the President) would finally break the sound barrier on March 4, 1948. He reached Mach 1.1 three weeks later.

More Information

Venera 4 (NASA)

NASA Armstrong Fact Sheet: First Generation X-1 (NASA)