Mad About Science: Early rocketry

By Brenden Bobby
Reader Columnist

The first time humans took flight in an artificial aircraft occurred 120 years ago. That may seem like ancient history; but, when you consider that our primary mode of transportation for the previous 10,000 years had been by foot, hoof and wheel, that’s shockingly recent. 

Even more recent, but intrinsically linked to flight, is the development of rockets. On April 20, SpaceX launched the largest rocket ever developed in a test flight that lasted approximately four minutes. The flight ended in an explosion, which to an outside observer may appear to be a failure. In fact, destruction was its ultimate goal, and the fact that it survived for four minutes provided a wealth of knowledge that may well take months or even years to fully digest.

Human fascination with rocketry began sometime around 1200 CE, when Chinese armies used portable rockets as artillery for war. This technology developed rapidly in eastern Asia, eventually leading to the invention of the hwacha in Korea in the 1590s. The hwacha was an artillery cart that was loaded with arrows strapped with directional explosives — tiny rockets similar to the bottle rockets we fire off for the Fourth of July. This weapon was capable of firing up to 200 arrows before it needed to be reloaded.

The V-2 rocket. Photo courtesy SPL.

The hwacha was designed with a special use in mind: to repel and kill sea pirates and raiders from Japan that frequently pillaged the Korean coastline. These organ guns would be mounted from high vantage points and pepper invading vessels in a hail of rocket-powered arrows — a nightmarish experience straight out of a match of Warhammer: Age of Sigmar. 

Imagine yourself trapped in a boat while hundreds of arrows hail down on you from the sky. There’s no way you can reach your attacker, there’s nowhere to escape or hide, you’re simply at the mercy of a cruel experiment in physics.

By the 1930s, more efficient forms of fuel had been discovered, as well as more reliable ways to expend that fuel. Rockets are more technical than spraying fuel from one end and setting it on fire. Pulse jets are designed to release fuel in rapid spurts to accelerate the rocket without blasting all of the fuel right away.

This type of rocket was first developed in Germany in 1935, though it wouldn’t begin testing until 1941, two years after Adolf Hitler invaded Poland and triggered the largest conflict in human history. This rocket was called the V-1. 

In rocketry, V is a common sight. Delta-v is the entire basis of how we calculate the movement of rockets and spacecraft, especially when making orbital maneuvers to reach other celestial bodies like the moon or Mars. The “v” in Delta-v stands for velocity, while the term “Delta-v” is a term for change of velocity. If you’re looking for a more in-depth look at Delta-v, there are a number of books on physics and rocketry available for check-out and perusal at the library.

That said, the “V” in “V-1” does not stand for velocity. Instead, it’s a German word: Vergeltungswaffe, which roughly translates to “vengeance weapon.” The “1” in the name denotes that it was the first such “vengeance weapon,” and indeed it was the first iteration of rockets that would influence military, government and private rockets to follow for the next 90 years and counting.

The V-1 was first used in combat by the Nazis to bombard London after the allied invasion of Normandy. As the allies pushed deeper into France and then Germany, the frequency of V-1 attacks decreased. It had a range of about 160 miles and was the size of a small plane, though it packed enough of a punch to leave a 100-foot crater anywhere it impacted.

The V-2 rocket was the successor of the V-1. The V-2 was considerably larger than its predecessor, standing 45 feet tall and with a 200-mile operational range. During a test flight, the V-2 became the first rocket to achieve a sub-orbital flight, soaring 109 miles into the air before coming back down. This was the first artificial construct to reach space.

The intention of this rocket wasn’t to achieve orbit, and its historic sub-orbital flight was the result of a test to see how high it could travel. It’s purpose was to rain even more destruction on London. However, after years of research, trial and error — critically employing the scientific knowledge and rocketry experience of captured German scientists after the war — we discovered more optimal ways to achieve orbit (calculated, of course, with the assistance of Delta-v). 

The angle at which a rocket ascends is pivotal in its ability to achieve orbit. Traveling in a path straight upward means the rocket is fighting against gravity more than if it were traveling at a 45-degree angle. 

It’s difficult to tell from the ground, but rockets begin to bank at roughly a 30- to 45-degree angle, eastward, after about 10,000 meters. The higher the rocket travels, the less dense the atmosphere becomes, which means the rocket doesn’t have to expend as much energy to push through air. Similarly, the pull of Earth’s gravity becomes weaker as the rocket travels farther from the surface. By accelerating at an angle, the rocket slings around the Earth, aided partially by Earth’s gravity.

Imagine yourself with a yo-yo. Throw that yo-yo straight outward, and it’s just going to reach the end of its string and fall, right? Now try throwing the yo-yo to the left or the right — it will probably do something similar. Now try spinning with the yo-yo. The centrifugal force of your spin will cause the yo-yo to orbit you, staying aloft as you spin around. This is essentially the same thing that’s happening to a rocket orbiting around a spherical Earth.

Want to experience some rocketry first-hand? Stop by the library on Saturday, May 13 at 9 a.m. to participate in Spacepoint’s rocketry challenge. 

Geared toward students between fourth and 12th grade, participants will get to learn about rocketry while building, customizing and then launching their own rocket capable of traveling more than 300 vertical feet. Trust me: This is an event you won’t want to miss, so be sure to register at ebonnerlibrary.org/events.

Stay curious, 7B.