A Closer Look At The Third Stage Propelling Rocket Lab To Success
Rocket Lab’s Electron launch vehicle has been making some very impressive progress in the last couple of years. Between reusability developments, a significant launch cadence increase, and unique missions like CAPSTONE, the rocket is making a mark within the industry. However, being a small lift launch vehicle, Electron is limited in some of its capabilities.
This is where the Kick Stage and Photon spacecraft come into play. Also known as Electron’s third stage, these additional spacecraft turn Electron into a much more capable and mission specific rocket. In its simplest form, the Kick Stage serves as in-space propulsion to deploy payloads to orbit. In its most advanced configuration, the Kick Stage becomes Photon, Rocket Lab’s satellite bus that supports several-year duration missions to LEO, MEO, Lunar, and interplanetary destinations.
What at first sounds like an impossible mission with a small lift launch vehicle, becomes well within the ability of Electron thanks to these spacecraft. A feature that Rocket Lab is continuing to develop and use for even more ambitious missions. Here I will go more in-depth into the design of the kick stage and Photon, the exact difference, their past and future application, and more.
Kick Stage & Photon
The Rocket Lab Kick Stage is designed to deliver small satellites to precise and unique orbits, whether flying as dedicated or rideshare on Electron. The Kick Stage’s propulsion system consists of Rocket Lab’s in-house designed and built Curie engine, six low minimum impulse bit cold gas Reaction Control System thrusters, tank pressurization system, and high propellant mass fraction tanks which can be scaled to meet mission-specific needs. Curie is an additively manufactured, pressure-fed engine with flight heritage across more than a dozen orbital missions. It is a storable, re-startable, bipropellant liquid propellant engine integrated with lightweight composite propellant tanks and valves into a single compact module.
In addition, as the small satellite industry experiences rapid growth, orbital debris becomes a greater concern. Traditional methods of deploying satellites can leave large rocket stages in orbit, contributing to the global issue of space debris. The Kick Stage has been designed with the capability to deorbit itself on an accelerated time scale, well before the 25 year deorbit guidelines stipulated by NASA. By performing a deorbit burn with the Curie engine, Rocket Lab can lower the Kick Stage’s perigee to increase aerodynamic drag on the spacecraft and cause it to deorbit within months or single digit years, as required.
However, for missions that require extended payload support on orbit, or for missions exceeding 2,000 km to MEO, lunar, or interplanetary destinations, Rocket Lab offers the Photon spacecraft bus, a high-performance evolution of the Kick Stage. Photon is a configurable, modular spacecraft designed to accommodate a variety of payloads and instruments without significant redesign. Photon is equipped with radiation-tolerant avionics, deep space-capable communications and navigation technology, and high-performance space-storable propulsion capable of multiple restarts on orbit. With the capacity to both host an external payload and perform secondary mission objectives as a separate operational spacecraft, Photon has been designed for dedicated mission or as a rideshare option without the programmatic complexity, expanded cost, and schedule risk typically experienced when launching with a medium or heavy lift launch vehicle.
Photon flies as the upper stage of Electron, eliminating the parasitic mass of deployed spacecraft and enabling full utilization of the fairing. As a configurable platform, Photon can be tailored to meet unique mission requirements. From mass manufacture as a streamlined constellation offering, to a single customized technology demonstration spacecraft, Photon can easily be adapted to make different missions possible. Even the Kick Stage has successfully deployed multiple satellites flying as rideshare payloads to different orbits on the same mission. One past example includes Rocket Lab’s 10th Electron mission, ‘Running Out of Fingers’, launched in December 2019. The Kick Stage’s Curie engine was ignited to circularize the orbit, before deploying a payload to 400 km. Curie then re-ignited to lower the altitude to 360 km, where the remaining payloads were deployed. One unique feature of many that both the kick stage and Photon spacecraft offer Rocket Lab within Electron.
Past & Future Applications
Now that we know more about the Kick Stage and Photon spacecraft, we can take a closer look at some unique missions that highlight the value of these third stages. Years ago in 2020, Rocket Lab launched it’s first in-house designed and built operational satellite. The satellite, named ‘First Light’, was the first spacecraft from Rocket Lab’s family of configurable Photon satellites to be deployed to orbit. Launched as a technology demonstration, ‘First Light’ built upon the existing capabilities of the Electron launch vehicle’s Kick Stage with additional subsystems to enable long duration satellite operations. This pathfinding mission was an initial demonstration of the new power management, thermal control, and attitude control subsystem capabilities.
One of the most known and recent examples of this system was the CAPSTONE mission. In July of last year, Rocket Lab announced it had successfully deployed a pathfinding satellite for NASA, setting it on a course to the Moon. The deployment marked the successful completion of Rocket Lab’s first deep space mission, paving the way for the Company’s upcoming interplanetary missions to Mars and Venus. Rocket Lab’s role in the mission took place over two phases. First, CAPSTONE was successfully launched to low Earth orbit by Rocket Lab’s Electron launch vehicle on June 28th. From there, Rocket Lab’s Lunar Photon spacecraft provided in-space transportation, power, and communications to CAPSTONE. After six days of orbit-raising burns by Lunar Photon’s 3D printed HyperCurie engine, CAPSTONE was deployed on its ballistic lunar transfer trajectory to the Moon as planned at 07:18 UTC on July 4th.
In addition to providing the launch, Rocket Lab designed, manufactured, and operated the Lunar Photon spacecraft, successfully completing a highly complex deep space mission and demonstrating Rocket Lab’s growing capabilities as an end-to-end space company. Here, the company was able to send a payload to the Moon with a small lift launch vehicle. At the time Rocket Lab founder and CEO Peter Beck commented, “We pushed Electron and Photon to their limits and proved it’s possible to do big missions with small spacecraft. Now we’ll be applying this ground-breaking technology for more interplanetary journeys, including our upcoming missions to Venus and Mars.”
In this case, Rocket Lab is in the process of preparing for two separate missions that will rely on the Photon spacecraft. Specifically, research suggests Venus was once a habitable planet similar to Earth. A 2019 study from NASA’s Goddard Institute for Space Studies found that Venus could have had shallow oceans on the surface for two to three billion years and this would have supported temperatures of between 68 to 122 degrees Fahrenheit. Rocket Lab is sending the first private mission to Venus in search of supporting evidence of organic compounds in the cloud layer – traces of life. The goal, using an Electron launch vehicle and Photon spacecraft, is to send a probe to around 30 miles’ altitude, where Venus’ atmospheric conditions are closer to those found on Earth.
Also, the company is currently manufacturing two interplanetary Photon spacecraft for a science mission to Mars, delivering Decadal-class science at a fraction of the cost of typical planetary missions. The Escape and Plasma Acceleration and Dynamics Explorers (ESCAPADE) mission will orbit two Rocket Lab-built Photon spacecraft around Mars to understand the structure, composition, variability, and dynamics of Mars’ unique hybrid magnetosphere. The mission will also support crewed exploration programs like Artemis through improved solar storm prediction.
Following deployment from a NASA-provided commercial launch vehicle, the pair of Photons will conduct an 11-month interplanetary cruise before inserting themselves into elliptical orbits around Mars to begin the science phase. Both Photons incorporate satellite subsystems developed and manufactured by Rocket Lab, including star trackers, reaction wheels, ranging transceivers for deep space navigation, and in-space propulsion systems. By leveraging vertically-integrated spacecraft manufacturing, the ESCAPADE mission will be delivered at a fraction of the cost of traditional planetary missions. Peter Beck, said “ESCAPADE is an innovative mission that demonstrates that advanced interplanetary science is now within reach for a fraction of traditional costs, and we’re proud to make it possible with Photon.” Something we can look forward to in the coming years.
Conclusion
The Electron launch vehicle has proved its importance and consistency over the course of multiple years now. Despite the fact that it’s a small lift launch vehicle, it has already sent a payload to the Moon and has another mission to Venus not long from now. All of which would not be possible if it weren’t for the Photon and Kick Stage spacecraft. Together they allow unique and distant missions, deorbiting, payload deployment options, and more. We will have to wait and see how it progresses and the impact it has on the space industry.