Introducing the Phase Four megaconstellation engine

Beau Jarvis
Nov 21 · 5 min read

The first wave of internet megaconstellations spun up in the 1990s. Motorola spun up the 66 satellite Iridium constellation. Qualcomm teamed with Loral to build the 48 satellite Globalstar constellation. Bill Gates got into the race, funding Teledesic and its target 840 satellite constellation.

If you don’t recognize these names, it’s because they all failed. Iridium took thirteen years to design, develop, and deploy its constellation, blowing through $5B. Globalstar spent ten years and $4B getting its constellation into orbit. Both Iridium and Globalstar declared bankruptcy and were subsequently restructured; Teledesic went out of business before launching a single spacecraft. A slew of business school case studies (read: autopsies) later, the overwhelming cause of death was the long time to market. In the decade-plus it took to get to space, ground-based cellular networks expanded and gobbled up these constellations’ target market.

What’s different for today’s new megaconstellations? What do OneWeb, SpaceX’s Starlink, and Amazon’s Project Kuiper have that Teledesic and others didn’t? For one, launch costs have come down and access to space has improved. That certainly brings down the cost of deploying a megaconstellation, lowering the overall risk of the venture. Is that enough?

At Phase Four, we believe these ventures need to be further de-risked before launch. Where the 90s constellations maxed out at hundreds of spacecraft, today’s megaconstellations are more ambitious than ever. They seek to design, build, and launch thousands — that’s an order of magnitude more spacecraft. The single biggest blocker in their supply chains is the primary propulsion system. Primary propulsion is not a train or a bus that drops you off near your neighborhood; it’s a crucial system that enables a spacecraft to achieve its target altitude, safely deorbit at end of life, and extend its useful lifetime through orbit maintenance. This lifetime extension boosts the revenue each spacecraft can generate.

The dream of the 90s is alive at Phase Four

(with apologies to the Portlandia team)

We think in-space propulsion should be as easy as driving a car. We take for granted that when we buy a car, its gas tank and its various valves and manifolds are included. In the electric propulsion industry, legacy providers sell thrusters, but power processing units, propellant tanks, and software are sold separately.

And while you can drive a car off of the sales lot the same day, you need deep, highly-specialized electric propulsion knowledge to install and operate these traditional engines. But you have time to learn — they’re delivered a year or more after they’re ordered. They’re complicated to build and rely on failure-prone components, making them difficult to manufacture at scale. With available inventory, Phase Four’s simple propulsion systems have a lead time of two months or less.

The five step Phase Four assembly and test process

We call our propulsion systems “plug and play” because they just work. Embedded software means you don’t have to be a propulsion expert to fulfill your mission objectives. A simple propulsion system is make or break for today’s megaconstellations. It’s the difference between building your fleet in years, or in decades.

The Sprite engine for megaconstellations

We’re excited to share that we’ve begun development on a revolutionary plasma propulsion system called Sprite. Phase Four’s Sprite engine generates plasma using water. That plasma is then accelerated out of your spacecraft, creating thrust. Like all of Phase Four’s engines, Sprite is based off of our RF thruster architecture, so it’s lightweight, compact, and mass-manufacturable.

Why’s it called Sprite?

You might think of magical creatures or the lemon-lime soda, but Phase Four’s Sprite engine is inspired by a meteorological sprite. Our water plasma’s pink glow reminded us of atmospheric sprites. Atmospheric sprites are plasma phenomena that appear as beautiful, bright red flashes of light high above storm clouds, when lightning is discharged into the upper atmosphere and ionosphere.

Tendrils of a glowing sprite over Costa Rica, captured by Doug Parker

Why water, and why now?

1. Water is safe. I’m proud to share that Phase Four has joined the Space Safety Coalition. Phase Four’s development of the Sprite engine is part of our commitment to space safety. Water is a unique propellant that is 1) non-toxic, 2) chemically inert, and 3) densely stored. This last point means that Sprite avoids highly pressurized (read: thousands of PSI) storage vessels — vessels that create catastrophic debris if they fail. This debris would create a cascading effect in a valuable orbit. In addition, water propellant is non-toxic and non-corrosive.

2. Water is sustainable. Traditional EP engines rely on xenon, a heavy gas that’s rare on Earth and even rarer in space. Phase Four’s Sprite engine powers humanity’s future in space with in-space resources, capitalizing on abundant ice and liquid water found throughout our solar system. Despite being named the Blue Planet for the large oceans on its surface, the Earth’s water volume is dwarfed by four of Jupiter and Saturn’s moons.

Source: Business Insider

Water plasma RF engines are easily refuelable and ideal for deep space infrastructure. There’s no need to use 1) electrolysis to split water into its component hydrogen and oxygen, or 2) pressurized storage.

3. Water has potential as a high performance propellant. Research out of the University of Washington and the University of Maryland shows high peak thrust efficiency with water vapor as a propellant, and correspondingly, high specific impulse. If any team has the ability to bring the Sprite engine to market, it’s the Phase Four team. This is the team that took a xenon-based RF thruster from 0.25% to 15% thrust efficiency in less than two years.

Phase Four water thruster firing in vacuum.

4. Water is cost-effective. This means that 1) the propellant itself is inexpensive, 2) hardware costs come down because you no longer need a vessel that can withstand high pressure, and 3) a water engine is lighter and more compact than traditional krypton-fueled engines, further reducing launch costs. Taken together, these three cost reductions represent a 60% reduction over the cost of deploying a krypton-based Hall thruster. Across 1,000 spacecraft, Phase Four conservatively estimates that these savings represent over $150M in cost savings. Across 30,000 spacecraft, that’s nearly $5B (again conservatively).

Note that these estimates don’t take into account the faster time to deployment Phase Four’s propulsion systems enable, and the missed revenues associated with using traditional EP engines. Getting to market faster means generating revenue faster.

The Sprite engine truly rises to the challenge of next-generation megaconstellations. I could not be more excited to keep pushing human progress forward with the Phase Four team.

Plasma Matters

The Phase Four Blog

Beau Jarvis

Written by

I ❤ plasma electric propulsion

Plasma Matters

The Phase Four Blog

Welcome to a place where words matter. On Medium, smart voices and original ideas take center stage - with no ads in sight. Watch
Follow all the topics you care about, and we’ll deliver the best stories for you to your homepage and inbox. Explore
Get unlimited access to the best stories on Medium — and support writers while you’re at it. Just $5/month. Upgrade