The future low Earth orbit (LEO) economy depends on faster, more frequent rides to space. SEOPS, LLC is addressing this urgent need with its SlingShot system, an innovative small satellite (smallsat) deployer that hitches a ride on Northrop Grumman’s Cygnus resupply spacecraft and releases smallsats into a higher Earth orbit above that of the International Space Station (ISS). As a commercial facility on commercial resupply launch vehicles servicing the ISS, SlingShot offers a flexible, affordable rideshare for smallsats and provides the longer in-orbit time needed to prove out technology critical to the successful commercialization of LEO.
SEOPS, an ISS U.S. National Laboratory Commercial Service Provider based in Houston, has completed four SlingShot missions since the facility’s first deployment in February 2019. SlingShot provides opportunities for smallsat deployments in a cost-effective manner that aligns with the current resupply flight schedule. The higher-orbit trip comes after Cygnus completes its primary commercial resupply services mission to the ISS. SEOPS designed and built SlingShot from scratch and secured its own customers for use of the facility—completing NASA’s safety review process in only three months and fully deploying in less than a year, said SEOPS CEO Chad Brinkley.
"Our approach serves as a blueprint for the commercialization model embraced by NASA," said Brinkley, "where the private sector will lead space launch and operational advances into LEO, and NASA can be one of many customers."
SlingShot has expanded LEO access to a broad array of users—from NASA to commercial firms and universities—allowing them to raise the readiness level of their technology at greatly reduced cost and risk. By de-risking technology development and demonstration, SlingShot is helping to democratize LEO and to accelerate the development of a robust and sustainable LEO market economy.
Building a Strong Partnership
SEOPS partners with Northrop Grumman on SlingShot missions—for its first SlingShot mission, Cygnus initially delivered more than 7,400 pounds of science and supplies to the ISS. To date, SlingShot has deployed 14 CubeSats and supported four hosted payloads. Northrop Grumman’s Cygnus first began flying missions above the ISS in November 2016 to facilitate NASA science objectives, including CubeSat deployments. Early extended Cygnus missions included the Saffire Fire Experiment led by researchers at NASA Glenn Research Center and the OA-4 mission, where Cygnus helped perform re-entry observations.
After Cygnus berths to the ISS, ISS crew members install the SlingShot deployers onto the front of Cygnus using a custom modular bracket, which houses the cluster of deployers. Cygnus then moves to a safe distance from the station before Northrop Grumman flight controllers in Dulles, Virginia, propel the vehicle to a higher altitude where they deploy the payloads. Cygnus then re-enters Earth’s atmosphere and burns up harmlessly over the Pacific Ocean.
Dave Hastman, vice president of exploration and operations for Northrop Grumman, operator of the Cygnus spacecraft, says carrying secondary payloads on Cygnus requires working within a compressed schedule. “The combined Cygnus and SEOPS team has learned significant lessons to facilitate continued successful operation of the SlingShot deployer and hosted payloads,” Hastman said.
Currently, eight out of ten SlingShot users are government clients, including NASA, the Department of Defense, and the U.S. Air Force. The Air Force and Texas-based Hypergiant Industries, an artificial intelligence satellite tech company, plan to use SlingShot to test the Air Force’s Chameleon Constellation of LEO-based reconfigurable satellites. The Air Force designed this new breed of military satellites to re-task and respond in minutes to space threats, from new orbital debris to a conventional weapon or a cyberattack.
Flexible Launch Options
Over the past decade, there has been a significant rise in the number of smallsats being launched into orbit. CubeSats, small cube-shaped satellites measuring 10 cm on each side and weighing less than 1.4 kg (or about three pounds), accounted for 42% of all smallsats and 33% of all satellites launched into orbit last year. The number of CubeSats launched increased seven-fold from 2012 to 2019, according to analytics and engineering firm Bryce Space and Technology. The ISS has played a key role in enabling this rapid increase—more than 300 CubeSats had been launched from the space station as of January 2020, and SlingShot is helping to expand access even further.
In addition to deploying CubeSats, SlingShot can also host fixed payloads that remain attached to Cygnus while it is in orbit. These fixed payloads use Cygnus as a satellite bus for power, attitude (position in space) control, and communications for longer missions.
While the ISS operates 350 kilometers from the ground, SlingShot reaches 450 to 480 kilometers above the Earth via Cygnus’s post-ISS-berth orbit. This higher orbital path provides “a sweet spot for mission duration and Earth coverage” that allows you to see 90% of the Earth, Brinkley said, noting that the higher a payload launches into orbit, the longer it can remain in microgravity to conduct tests and prove out its technology.
A SlingShot Success Story
One successful SlingShot user is Lynk, a startup that has completed four successful technology demonstrations using SlingShot deployment—including sending the world’s first text message from an orbiting satellite to a standard mobile phone on Earth in February 2020. Lynk has raised $10 million since its first technology demonstration with SlingShot. Lynk is building a smallsat constellation to enable anywhere-anytime communications across the world using standard phones, with the goal of providing affordable cellular coverage everywhere on Earth. By connecting more people around the world, the company is helping to overcome the digital divide, which disproportionately affects developing nations and communities with low socioeconomic status. Connected communities can innovate faster and participate in the digital economy, which drives economic growth.
By leveraging SlingShot and the facility’s frequent rides on resupply missions, Lynk has been able to achieve rapid prototyping and development. Lynk’s first three SlingShot payloads were fixed payloads on Cygnus, and the company’s fourth payload used a free-flying microsatellite. “We have our fourth prototype up, and all have used SlingShot,” said Lynk co-founder and CEO Charles Miller, a 30-year serial space entrepreneur. “Our ultimate goal is delivering global broadband directly to your phone, everywhere. We want to bring connectivity to the 90% of Earth’s surface that is outside the bounds of terrestrial wireless.”
Using SlingShot, Lynk was able to deploy its technology faster while being capital efficient.
"We were able to focus our money on the payload," Miller said. "What’s critical to us in a commercially competitive market is how do you innovate fast? Part of that answer has been leveraging the ISS and SlingShot." Lynk launches a payload an average of once every six months, Miller said, and he considers SlingShot one of the most cost-effective options for smallsat launches. Building on Lynk’s successful demonstrations using SlingShot, the company is now developing its own free-flyer mission.
Student-Built CubeSats Leverage SlingShot
Academia is also benefiting from SlingShot’s flexible deployer. Last year, two CubeSats built by students from Northwest Nazarene University (NNU) in Nampa, Idaho, were launched into space using SlingShot. The students’ first CubeSat mission on SlingShot, Radio Frequency Tag Satellite (RFTSat), was developed in partnership with the Georgia Institute of Technology and deployed in August 2019. RFTSat tested a new 5.8 GHz radiofrequency tag sensor system using backscattering communication. This system will allow data collection from an array of small sensor tags located at the extremities of very large orbiting structures of the future. These postage-stamp-sized tags require no battery or wires—they are powered and read from a centralized reader using radiofrequency energy (the transfer of energy by radio waves).
“RFTSat can sense anything on a large space structure, from radiation to temperature to fields to vibrations—whatever sensors you want to put out there,” explains Stephen Parke, professor of electrical engineering and chair of physics and engineering at NNU. “The tags can last indefinitely because they don’t have any batteries.”
The students’ second CubeSat to use SlingShot, MakerSat-1, was deployed in February 2020 and utilized structural parts that were 3D printed onboard the ISS using Made In Space’s Additive Manufacturing Facility (AMF). Both MakerSat-1 and its precursor mission, MakerSat-0 from NNU, studied four polymers that can be used for 3D printing structures in space to see which would best endure the destructive orbital environment, where UV, plasma, and ionizing radiation are commonplace.
Parke says data from both MakerSat missions found that 3D printed polyactic acid (PLA) was best for short-term missions of one to three years, while Ultem® (polyetherimide/polycarbonate), a UV-resistant plastic material, would work best in longer-term missions.
Both SlingShot-deployed NNU CubeSats will likely remain in orbit for two or three years and have not experienced any orbital degradation so far, said Parke. He envisions space-based missions one day being devised on the fly onboard the ISS, using stowed satellite components that are snap-assembled with polymer AMF-printed structures and deployed into orbit from the ISS.
Into the Future
Looking ahead, SEOPS CEO Brinkley remains excited about the prospect of continuing to fly the SlingShot system, which provides a cost-effective, reliable way to get into upper orbit. Northrop Grumman reiterated its commitment for future SlingShot missions. “The Cygnus program envisions continuing to support SEOPS with the deployment of CubeSats and expanding on the successful hosted payload operations performed thus far,” Hastman said.
Brinkley says SlingShot’s success has opened up new opportunities for SEOPS to expand its core capabilities beyond launch systems to be a true systems integrator for missions beyond LEO.
“SlingShot has given us a lot of mission-critical past performance that translates to market credibility,” Brinkley said. “We know how to integrate our deployment systems successfully on any rocket with our team, not just the launch systems we build, and we have proven we can fly safely, leveraging the ISS infrastructure. I can’t think of a better model for commercialization of LEO.” [BY ANNE WAINSCOTT-SARGENT, CONTRIBUTING AUTHOR]Upward Magazine of the ISS National Lab. (http://https://www.issnationallab.org/iss360/slingshots-flexible-launch-model-offers-affordable-fast-path-to-leo/)