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SpinLaunch is building centrifuges to whip satellites from Earth into orbit—by 2025
At first, the dream of riding a rocket into space was laughed off the stage by critics who said you’d have to carry along fuel that weighed more than the rocket itself. But the advent of booster rockets and better fuels let the dreamers have the last laugh.
Hah, the critics said: To put a kilogram of payload into orbit we just need 98 kilograms of rocket plus rocket fuel.
What a ratio, what a cost. To transport a kilogram of cargo, commercial air freight services typically charge about US $10; spaceflight costs reach $10,000. Sure, you can save money by reusing the booster, as Elon Musk and Jeff Bezos are trying to do, but it would be so much better if you could dispense with the booster and shoot the payload straight into space.
The first people to think along these lines used cannon launchers, such as those in Project HARP (High Altitude Research Project), in the 1960s. Research support dried up after booster rockets showed their mettle. Another idea was to shoot payloads into orbit along a gigantic electrified ramp, called a railgun, but that technology still faces hurdles of a basic scientific nature, not least the need for massive banks of capacitors to provide the jolt of energy.
Imagine a satellite spinning in a vacuum chamber at many times the speed of sound. The gates of that chamber open up, and the satellite shoots out faster than the air outside can rush back in—creating a sonic boom when it hits the wall of air.
Now SpinLaunch, a company founded in 2015 in Long Beach, Calif., proposes a gentler way to heave satellites into orbit. Rather than shoot the satellite in a gun, SpinLaunch would sling it from the end of a carbon-fiber tether that spins around in a vacuum chamber for as long as an hour before reaching terminal speed. The tether lets go milliseconds before gates in the chamber open up to allow the satellite out.
“Because we’re slowly accelerating the system, we can keep the power demands relatively low,” David Wrenn, vice president for technology, tells IEEE Spectrum. “And as there’s a certain amount of energy stored in the tether itself, you can recapture that through regenerative braking.”
The company reports they've raised about $100 million. Among the backers are the investment arms of Airbus and Google and the Defense Innovation Unit, part of the U.S. Department of Defense.
SpinLaunch began with a lab centrifuge that measures about 12 meters in diameter. In November, a 33-meter version at Space Port America test-launched a payload thousands of meters up. Such a system could loft a small rocket, which would finish the job of reaching orbit. A 100-meter version, now in the planning stage, should be able to handle a 200-kg payload.
Wrenn answers all the obvious questions. How can the tether withstand the g-force when spinning at hypersonic speed? “A carbon-fiber cable with a cross-sectional area of one square inch (6.5 square centimeters) can suspend a mass of 300,000 pounds (136,000 kg),” he says.
How much preparation do you need between shots? Not much, because the chamber doesn’t have to be superclean. If the customer wants to loft a lot of satellites—a likely desideratum, given the trend toward massive constellations of small satellites–the setup could include motors powerful enough to spin up in 30 minutes. “Upwards of 10 launches per day are possible,” Wrenn says.
How tight must the vacuum be? A “rough” vacuum suffices, he says. SpinLaunch maintains the vacuum with a system of airlocks operated by those millisecond-fast gates.
Most parts, including the steel for the vacuum chamber and carbon fiber, are off-the-shelf, but those gates are proprietary. All Wrenn will say is that they’re not made of steel.
So imagine a highly intricate communications satellite, housed in some structure, spinning at many times the speed of sound. The gates open up, the satellite shoots out far faster than the air outside can rush back in. Then the satellite hits the wall of air, creating a sonic boom.
No problem, says Wrenn. Electronic systems have been hurtling from vacuums into air ever since the cannon-launching days of HARP, some 60 years ago. SpinLaunch has done work already on engineering certain satellite components to withstand the ordeal—“deployable solar panels, for example,” he says.
After the online version of this article appeared, several readers objected to the SpinLaunch system, above all to the stress it would put on the liquid-fueled rocket at the end of that carbon-fiber tether.
“The system has to support up to 8,000 gs; most payloads at launch are rated at 6 or 10 gs,” said John Bucknell, a rocket scientist who heads the startup Virtus Solis Technologies, which aims to collect solar energy in space and beam it to earth.
Keith Lostrom, a chip engineer, went even further. “Drop a brick onto an egg—that is a tiny fraction of the damage that SpinLaunch’s centripedal acceleration would do to a liquid-fuel orbital launch rocket,” he wrote, in an emailed message.
Wrenn denies that the g-force is a dealbreaker. For one thing, he argues, the turbopumps in liquid-fuel rockets spin at over 30,000 rotations per minute, subjecting the liquid oxygen and fuel to “much more aggressive conditions than the uniform g-force that SpinLaunch has.”
Besides, he says, finite element analysis and high-g testing in the company’s 12-meter accelerator “has led to confidence it’s not a fundamental issue for us. We’ve already hot-fired our SpinLaunch-compatible upper-stage engine on the test stand.”
SpinLaunch says it will announce the site for its full-scale orbital launcher within the next five months. It will likely be built on a coastline, far from populated areas and regular airplane service. Construction costs would be held down if the machine can be built up the side of a hill. If all goes well, expect to see the first satellite slung into orbit sometime around 2025.
This article was updated on 24 Feb. 2022 to include additional perspectives on the technology.
Philip E. Ross is a senior editor at IEEE Spectrum. His interests include transportation, energy storage, AI, and the economic aspects of technology. He has a master's degree in international affairs from Columbia University and another, in journalism, from the University of Michigan.
Ignoring atmospheric drag loss, launching vertically to 200 km altitude requires a velocity impulse v of more than 1950 m/s (mach 6).
Including drag loss, much more initial velocity impulse, before slamming through a wall of dense, high drag, surface-level air. For comparison, the SR-71 Blackbird flew at half the speed through 3% density air.
Centrifugal (sideways radial) acceleration is v²/R. If radius R is 50 meters, the radial acceleration for a 1950 m/s "rim velocity" is 76000 m/s², or 7800 gees.
Orbital rockets are liquid-propellant-filled tubes, and can't tolerate fractional gee high wind loads at launch, much less kilogee sideways loads that would shred strong structures and crumble solid rocket fuel.
A colleague wrote this response to me: "I was interviewing to be their Chief Engineer 3 or 4 years ago. I walked away telling them they were crazy - in more ways than you describe."
An engineer's professional responsibility is to protect the public from nonsense, not publish it. Please retract this article, and tell the public why. Newtonian physics is not "just another opinion".
Keith Lofstrom keithl@keithl.com
This is an April's fools joke, right?
It's a very good idea for putting Satellite into Eearths orbit. But if you want to put Astronauts into space by spin up Space Craft, you can also do that by keeping
The Astronauts Cabin on the centre of the Spin up Space Craft and he will not feel dizziness due to spin up of the space Craft ; because at the centre rotational velocity is negligible.
For Returning the Space Craft to earth with Astronauts, special booster rocket arrangement has to be made.
3,000x farther from Earth than Hubble—with a 25x greater download deluge
Technicians at Northrop Grumman Aerospace Systems facilities in Redondo Beach, Calif., work on a mockup of the JWST spacecraft bus—home of the observatory’s power, flight, data, and communications systems.
For a deep dive into the engineering behind the James Webb Space Telescope, see our collection of posts here.
When the James Webb Space Telescope (JWST) reveals its first images on 12 July, they will be the by-product of carefully crafted mirrors and scientific instruments. But all of its data-collecting prowess would be moot without the spacecraft’s communications subsystem.
The Webb’s comms aren’t flashy. Rather, the data and communication systems are designed to be incredibly, unquestionably dependable and reliable. And while some aspects of them are relatively new—it’s the first mission to use Ka-band frequencies for such high data rates so far from Earth, for example—above all else, JWST’s comms provide the foundation upon which JWST’s scientific endeavors sit.
As previous articles in this series have noted, JWST is parked at Lagrange point L2. It’s a point of gravitational equilibrium located about 1.5 million kilometers beyond Earth on a straight line between the planet and the sun. It’s an ideal location for JWST to observe the universe without obstruction and with minimal orbital adjustments.
Being so far away from Earth, however, means that data has farther to travel to make it back in one piece. It also means the communications subsystem needs to be reliable, because the prospect of a repair mission being sent to address a problem is, for the near term at least, highly unlikely. Given the cost and time involved, says Michael Menzel, the mission systems engineer for JWST, “I would not encourage a rendezvous and servicing mission unless something went wildly wrong.”
According to Menzel, who has worked on JWST in some capacity for over 20 years, the plan has always been to use well-understood K a-band frequencies for the bulky transmissions of scientific data. Specifically, JWST is transmitting data back to Earth on a 25.9-gigahertz channel at up to 28 megabits per second. The Ka-band is a portion of the broader K-band (another portion, the Ku-band, was also considered).
The Lagrange points are equilibrium locations where competing gravitational tugs on an object net out to zero. JWST is one of three craft currently occupying L2 (Shown here at an exaggerated distance from Earth). IEEE Spectrum
Both the data-collection and transmission rates of JWST dwarf those of the older Hubble Space Telescope. Compared to Hubble, which is still active and generates 1 to 2 gigabytes of data daily, JWST can produce up to 57 GB each day (although that amount is dependent on what observations are scheduled).
Menzel says he first saw the frequency selection proposals for JWST around 2000, when he was working at Northrop Grumman. He became the mission systems engineer in 2004. “I knew where the risks were in this mission. And I wanted to make sure that we didn’t get any new risks,” he says.
Besides, K a-band frequencies can transmit more data than X-band (7 to 11.2 GHz) or S-band (2 to 4 GHz), common choices for craft in deep space. A high data rate is a necessity for the scientific work JWST will be undertaking. In addition, according to Carl Hansen, a flight systems engineer at the Space Telescope Science Institute (the science operations center for JWST), a comparable X-band antenna would be so large that the spacecraft would have trouble remaining steady for imaging.
Although the 25.9-GHz K a-band frequency is the telescope’s workhorse communication channel, it also employs two channels in the S-band. One is the 2.09-GHz uplink that ferries future transmission and scientific observation schedules to the telescope at 16 kilobits per second. The other is the 2.27-GHz, 40-kb/s downlink over which the telescope transmits engineering data—including its operational status, systems health, and other information concerning the telescope’s day-to-day activities.
Any scientific data the JWST collects during its lifetime will need to be stored on board, because the spacecraft doesn’t maintain round-the-clock contact with Earth. Data gathered from its scientific instruments, once collected, is stored within the spacecraft’s 68-GB solid-state drive (3 percent is reserved for engineering and telemetry data). Alex Hunter, also a flight systems engineer at the Space Telescope Science Institute, says that by the end of JWST’s 10-year mission life, they expect to be down to about 60 GB because of deep-space radiation and wear and tear.
The onboard storage is enough to collect data for about 24 hours before it runs out of room. Well before that becomes an issue, JWST will have scheduled opportunities to beam that invaluable data to Earth.
JWST will stay connected via the Deep Space Network (DSN)—a resource it shares with the Parker Solar Probe, Transiting Exoplanet Survey Satellite, the Voyager probes, and the entire ensemble of Mars rovers and orbiters, to name just a few of the other heavyweights. The DSN consists of three antenna complexes: Canberra, Australia; Madrid, Spain; and Barstow, Calif. JWST needs to share finite antenna time with plenty of other deep-space missions, each with unique communications needs and schedules.
Sandy Kwan, a DSN systems engineer, says that contact windows with spacecraft are scheduled 12 to 20 weeks in advance. JWST had a greater number of scheduled contact windows during its commissioning phase, as instruments were brought on line, checked, and calibrated. Most of that process required real-time communication with Earth.
All of the communications channels use the Reed-Solomonerror-correction protocol—the same error-correction standard as used in DVDs and Blu-ray discs as well as QR codes. The lower data-rate S-band channels use binary phase-shift key modulation—involving phase shifting of a signal’s carrier wave. The K-band channel, however, uses a quadrature phase-shift key modulation. Quadrature phase-shift keying can double a channel’s data rate, at the cost of more complicated transmitters and receivers.
JWST’s communications with Earth incorporate an acknowledgement protocol—only after the JWST gets confirmation that a file has been successfully received will it go ahead and delete its copy of the data to clear up space.
The communications subsystem was assembled along with the rest of the spacecraft bus by Northrop Grumman, using off-the-shelf components sourced from multiple manufacturers.
JWST has had a long and often-delayed development, but its communications system has always been a bedrock for the rest of the project. Keeping at least one system dependable means it’s one less thing to worry about. Menzel can remember, for instance, ideas for laser-based optical systems that were invariably rejected. “I can count at least two times where I had been approached by people who wanted to experiment with optical communications,” says Menzel. “Each time they came to me, I sent them away with the old ‘Thank you, but I don’t need it. And I don’t want it.’”