How Flyback Rocket Boosters Got Off the Ground

What seems a rapid revolution was decades in the making

4 min read
A photo of a rocket booster landing on a landing pad.

On 14 April 2021, a Blue Origin booster landed after an uncrewed mission that reached an altitude of 106 kilometers.

Blue Origin

In the popular conception of a technological breakthrough, a flash of genius is followed quickly by commercial or industrial success, public acclaim, and substantial wealth for a small group of inventors and backers. In the real world, it almost never works out that way.

Advances that seem to appear suddenly are often backed by decades of development. Consider steam engines. Starting in the second quarter of the 19th century they began powering trains, and they soon revolutionized the transportation of people and goods. But steam engines themselves had been invented at the beginning of the 18th century. For 125 years they had been used to pump water out of mines and then to power the mills of the Industrial Revolution.

Lately we’ve become accustomed to seeing rocket boosters return to Earth and then land vertically, on their tails, ready to be serviced and flown again. (Much the same majestic imagery thrilled sci-fi moviegoers in the 1950s.) Today, both SpaceX and Blue Origin are using these techniques, and a third startup, Relativity Space, is on the verge of joining them. Such reusable rocketry is already cutting the cost of access to space and, with other advances yet to come, will help make it possible for humanity to return to the moon and eventually to travel to Mars.

Vertical landings, too, have a long history, with the same ground being plowed many times by multiple research organizations. From 1993 to 1996 a booster named DCX, for Delta Clipper Experimental, took off and landed vertically eight times at White Sands Missile Range. It flew to a height of only 2,500 meters, but it successfully negotiated the very tricky dynamics of landing a vertical cylinder on its end.

The key innovations that made all this possible happened 50 or more years ago. And those in turn built upon the invention a century ago of liquid-fueled rockets that can be throttled up or down by pumping more or less fuel into a combustion chamber.

In August 1954 the Rolls-Royce Thrust Measuring Rig, also known as the “flying bedstead,” took off and landed vertically while carrying a pilot. The ungainly contraption had two downward-pointing Rolls-Royce jet engines with nozzles that allowed the pilot to vector the thrust and control the flight. By 1957 another company, Hawker Siddeley, started work on turning this idea into a vertical take-off and landing (VTOL) fighter jet. It first flew in 1967 and entered service in 1969 as the Harrier Jump Jet, with new Rolls-Royce engines specifically designed for thrust vectoring. Thrust vectoring is a critical component of control for all of today’s reusable rocket boosters.

During the 1960s another rig, also nicknamed the flying bedstead, was developed in the United States for training astronauts to land on the moon. There was a gimbaled rocket engine that always pointed directly downward, providing thrust equal to five-sixths of the vehicle and the pilot’s weight, simulating lunar gravity. The pilot then controlled the thrust and direction of another rocket engine to land the vehicle safely.

It was not all smooth flying. Neil Armstrong first flew the trainer in March 1967, but he was nearly killed in May 1968 when things went awry and he had to use the ejection seat to rocket to safety. The parachute deployed and he hit the ground just 4 seconds later. Rocket-powered vertical descent was harder than it looked.

Vertical rocket landings have a long history, with the same ground being plowed many times by multiple research organizations.

Nevertheless, between 1969 and 1972, Armstrong and then five other astronauts piloted lunar modules to vertical landings on the moon. There were no ejection seats, and these have been the only crewed rocket-powered landings on a spaceflight. All other humans lofted into space have used Earth’s atmosphere to slow down, combining heat shields with either wings or parachutes.

In the early days of Blue Origin, the company returned to the flying-bedstead approach, and its vehicle took off and landed successfully in March 2005. It was powered by four jet engines, once again from Rolls-Royce, bought secondhand from the South African Air Force. Ten years later, in November 2015, Blue Origin’s New Shepard booster reached an altitude of 100 kilometers and then landed vertically. A month later SpaceX had its first successful vertical landing of a Falcon-9 booster.

Today’s reusable, or flyback, boosters also use something called grid fins, those honeycombed panels sticking out perpendicularly from the top of a booster that guide the massive cylinder as it falls through the atmosphere unpowered. The fins have an even longer history, as they have been part of every crewed Soyuz launch since the 1960s. They guide the capsule back to Earth if there’s an abort during the climb to orbit. They were last used in October 2018 when a Soyuz failed at 50 km up. The cosmonaut and astronaut who were aboard landed safely and had a successful launch in another Soyuz five months later.

The next big accomplishment will be crewed vertical landings, 50 years after mankind's last one, on the moon. It will almost certainly happen before this decade is out.

I’m less confident that we’ll see general-purpose quantum computers and abundant electricity from nuclear fusion in that time frame. But I’m pretty sure we’ll eventually get there with both. The arc of technology development is often long. And sometimes, the longer it is, the more revolutionary it is in the end.

This article appears in the April 2022 print issue as “The Long Road to Overnight Success .”

The Conversation (2)
Ashok Deobhakta19 Apr, 2022

Nice learning!

Robert Cain22 Mar, 2022

It’s interesting how many people skip right over the spacex grasshopper program. That was pretty important for their reusable booster development. I’m amazed at how many people don’t even realize it was a thing.

The Inner Beauty of Basic Electronics

Open Circuits showcases the surprising complexity of passive components

5 min read
A photo of a high-stability film resistor with the letters "MIS" in yellow.
All photos by Eric Schlaepfer & Windell H. Oskay

Eric Schlaepfer was trying to fix a broken piece of test equipment when he came across the cause of the problem—a troubled tantalum capacitor. The component had somehow shorted out, and he wanted to know why. So he polished it down for a look inside. He never found the source of the short, but he and his collaborator, Windell H. Oskay, discovered something even better: a breathtaking hidden world inside electronics. What followed were hours and hours of polishing, cleaning, and photography that resulted in Open Circuits: The Inner Beauty of Electronic Components (No Starch Press, 2022), an excerpt of which follows. As the authors write, everything about these components is deliberately designed to meet specific technical needs, but that design leads to “accidental beauty: the emergent aesthetics of things you were never expected to see.”

From a book that spans the wide world of electronics, what we at IEEE Spectrum found surprisingly compelling were the insides of things we don’t spend much time thinking about, passive components. Transistors, LEDs, and other semiconductors may be where the action is, but the simple physics of resistors, capacitors, and inductors have their own sort of splendor.

High-Stability Film Resistor

A photo of a high-stability film resistor with the letters "MIS" in yellow.

All photos by Eric Schlaepfer & Windell H. Oskay

This high-stability film resistor, about 4 millimeters in diameter, is made in much the same way as its inexpensive carbon-film cousin, but with exacting precision. A ceramic rod is coated with a fine layer of resistive film (thin metal, metal oxide, or carbon) and then a perfectly uniform helical groove is machined into the film.

Instead of coating the resistor with an epoxy, it’s hermetically sealed in a lustrous little glass envelope. This makes the resistor more robust, ideal for specialized cases such as precision reference instrumentation, where long-term stability of the resistor is critical. The glass envelope provides better isolation against moisture and other environmental changes than standard coatings like epoxy.

15-Turn Trimmer Potentiometer

A photo of a blue chip
A photo of a blue chip on a circuit board.

It takes 15 rotations of an adjustment screw to move a 15-turn trimmer potentiometer from one end of its resistive range to the other. Circuits that need to be adjusted with fine resolution control use this type of trimmer pot instead of the single-turn variety.

The resistive element in this trimmer is a strip of cermet—a composite of ceramic and metal—silk-screened on a white ceramic substrate. Screen-printed metal links each end of the strip to the connecting wires. It’s a flattened, linear version of the horseshoe-shaped resistive element in single-turn trimmers.

Turning the adjustment screw moves a plastic slider along a track. The wiper is a spring finger, a spring-loaded metal contact, attached to the slider. It makes contact between a metal strip and the selected point on the strip of resistive film.

Ceramic Disc Capacitor

A cutaway of a Ceramic Disc Capacitor
A photo of a Ceramic Disc Capacitor

Capacitors are fundamental electronic components that store energy in the form of static electricity. They’re used in countless ways, including for bulk energy storage, to smooth out electronic signals, and as computer memory cells. The simplest capacitor consists of two parallel metal plates with a gap between them, but capacitors can take many forms so long as there are two conductive surfaces, called electrodes, separated by an insulator.

A ceramic disc capacitor is a low-cost capacitor that is frequently found in appliances and toys. Its insulator is a ceramic disc, and its two parallel plates are extremely thin metal coatings that are evaporated or sputtered onto the disc’s outer surfaces. Connecting wires are attached using solder, and the whole assembly is dipped into a porous coating material that dries hard and protects the capacitor from damage.

Film Capacitor

An image of a cut away of a capacitor
A photo of a green capacitor.

Film capacitors are frequently found in high-quality audio equipment, such as headphone amplifiers, record players, graphic equalizers, and radio tuners. Their key feature is that the dielectric material is a plastic film, such as polyester or polypropylene.

The metal electrodes of this film capacitor are vacuum-deposited on the surfaces of long strips of plastic film. After the leads are attached, the films are rolled up and dipped into an epoxy that binds the assembly together. Then the completed assembly is dipped in a tough outer coating and marked with its value.

Other types of film capacitors are made by stacking flat layers of metallized plastic film, rather than rolling up layers of film.

Dipped Tantalum Capacitor

A photo of a cutaway of a Dipped Tantalum Capacitor

At the core of this capacitor is a porous pellet of tantalum metal. The pellet is made from tantalum powder and sintered, or compressed at a high temperature, into a dense, spongelike solid.

Just like a kitchen sponge, the resulting pellet has a high surface area per unit volume. The pellet is then anodized, creating an insulating oxide layer with an equally high surface area. This process packs a lot of capacitance into a compact device, using spongelike geometry rather than the stacked or rolled layers that most other capacitors use.

The device’s positive terminal, or anode, is connected directly to the tantalum metal. The negative terminal, or cathode, is formed by a thin layer of conductive manganese dioxide coating the pellet.

Axial Inductor

An image of a cutaway of a Axial Inductor
A photo of a collection of cut wires

Inductors are fundamental electronic components that store energy in the form of a magnetic field. They’re used, for example, in some types of power supplies to convert between voltages by alternately storing and releasing energy. This energy-efficient design helps maximize the battery life of cellphones and other portable electronics.

Inductors typically consist of a coil of insulated wire wrapped around a core of magnetic material like iron or ferrite, a ceramic filled with iron oxide. Current flowing around the core produces a magnetic field that acts as a sort of flywheel for current, smoothing out changes in the current as it flows through the inductor.

This axial inductor has a number of turns of varnished copper wire wrapped around a ferrite form and soldered to copper leads on its two ends. It has several layers of protection: a clear varnish over the windings, a light-green coating around the solder joints, and a striking green outer coating to protect the whole component and provide a surface for the colorful stripes that indicate its inductance value.

Power Supply Transformer

A photo of a collection of cut wires
A photo of a yellow element on a circuit board.

This transformer has multiple sets of windings and is used in a power supply to create multiple output AC voltages from a single AC input such as a wall outlet.

The small wires nearer the center are “high impedance” turns of magnet wire. These windings carry a higher voltage but a lower current. They’re protected by several layers of tape, a copper-foil electrostatic shield, and more tape.

The outer “low impedance” windings are made with thicker insulated wire and fewer turns. They handle a lower voltage but a higher current.

All of the windings are wrapped around a black plastic bobbin. Two pieces of ferrite ceramic are bonded together to form the magnetic core at the heart of the transformer.

This article appears in the February 2023 print issue.