You can’t always get what you want, but…

The room filled with the usual suspects and small talk. This year it seemed an unwritten rule that before any presenter could talk about their good work there came this certain chart. It was the late 1990’s, exciting times when ever faster computers, internet connections and aerospace technology came together to spur dreams of things to come. This chart was part of that. The future was simple, or so it seemed, a series of steps from today and getting something to Earth orbit costing $10,000 a pound to a fully reusable launcher costing just $1,000 a pound, and so on down the road. In a generation we will fly in machines merely 100 times more expensive than hopping aboard a flight to Atlanta. As expensive as that might seem it would be worlds cheaper than where we were.

Caggiano, Jackson, Muckstadt, Cornell University “Simulating Ground Support Capability for NASA’s Reusable Launch Vehicle Program”.

It was not quite so simple. The X-33, and next generation air-breathing vehicles launched from magnetic levitation catapults, among many technologies and systems NASA invested in, came and went. All the parts and pieces of hardware and studies never ended as flying machines. The costs would not drop just then, not yet, nor the prices atop those costs. At the time though, the lack of certainty on dropping the price of getting to space did not keep people from jumping to what they might pack as luggage once cheap rides became available. A special relationship between the ride to space and what goes inside the ride persists to this day.

One of the ideas back in the late 1990s for what might be the luggage for cheaper rides was Space Solar Power (SSP, or later ‘SBSP’ after a 2007 DOD study changed the name), a rebirth of an idea going back many decades. The champion for this idea was John Mankins at NASA Headquarters Office of Advanced Concepts and Technology. If NASA investments were to make getting to space cheaper, it would follow that the rides at these lower prices would also be increasingly for other than NASA and government agencies. Power stations in space were a natural next step.

Here in sunny Florida, a homeowner might get 5 to 6 hours a day of wonderful sunlight for their solar panels, and rather less on each side of that time as the sun rises and sets or when the weather is bad. Space Solar Power imagined a sun that never sets. Solar panels placed in Earth orbit would always face the sun and always transmit power to Earth 24 hours a day all year. This was not just a redirection of light, rather the power stations in space would transmit to Earth the power they received from sunlight after a conversion to microwaves. These were heady times when all this and more seemed possible. The power stations were massive, which is why they needed the transport cost to get down to that mere $100 a pound.

The vehicles however were not quite massive, so SSP would make up for that with a high launch rate. If a launch a week today makes for exciting times, the need here was for launches per day. It was on this side of the equation that a team at NASA Kennedy Space Center (myself included) were recruited to run the numbers. How many launches a day were possible given these technologies (if they became real that is)? Were the vehicle designs arguably consistent with launches per day? On what vehicles might this happen best, out of the assortment that seemed to grow every day, from pure rockets, to airbreathers, from larger to smaller, or single to two stage, but always reusable to be sustainable.

Mankins saw another link though beyond just a commercial opportunity and a world hungry for power, a demand to attach to a supply of vehicles. This was about more than just NASA moving toward being “one of many customers” for a ride (a phrase that did not become routine till decades later). Climate change was here and now, and what could NASA do about it?

The room had amphitheater seating, and the lights were dimmed during presentations. At our turn we had done our best to show how multiple launches a day were possible, to show the promise of how the far-away and impossible could be near and not so far-fetched. That is, if the designs from the vehicle teams had certain qualities (all big “ifs”), technology advanced and mature and robust beyond anything at the time, meaning launch rates and prices to build huge solar power stations in space were possible. These would be affordable, operable launch vehicles, close cousins to the airliners that opened air travel to the general public, rather than just the rich or the subsidized snail mail. For all the good work though, it was here in this dim setting as presenter after presenter chimed on that it dawned on me and others that all this was not enough. The dim setting was appropriate to the epiphany.

An advanced aircraft-like hypersonic vehicle separating from a launch assist rail on it's way to orbit. Image credit: NASA.
If we did not quite have the technology for the vehicle and the engines to add up to achieving orbit, we could help the takeoff with a few miles of advanced rail (think Battlestar Galactica style or helping a jet off the deck of an aircraft carrier.) Credit: NASA.

The real problem was the demand for power on Earth grew faster than we could throw power towers in space at it. Even if what we could build made us look like an advanced alien race in its infrastructure heyday, it was far from what was needed. When I turn to Mankins though, he is not surprised. Perhaps he already sensed the outcome. Adding up more detailed and better numbers across many experts and teams had not fundamentally changed the range on any of them from the start. Yet somehow this philosophical resignation was matched by a desire to push on that persists to this day. Further progress after all would make the entire range move, eventually closing in on the target and adding up to power from space as fast as it was needed.

At the time though, the numbers were staring at us all. Earth needs power, and even putting a massive solar power tower in space every year with thousands of tons of mass did not add up to keeping up with growing power demand on Earth. For perspective, the largest available semi-reusable launch vehicle today, the Falcon Heavy, can put up about 35 tons at a time if it’s side-boosters return to the launch site and its center booster lands on a drone ship at sea. Even if it might add up on launch frequency, that 35 tons today is still too expensive, as much headway as it’s made to lower costs from where we were.

Of course, we could see a day when with just more launches and even lower prices the power towers in space actually could keep up with Earthly demand for abundant, clean energy. The space tower technology itself could also get less expensive with time and more innovations like modules to ease manufacture on Earth. There would be experiments on Earth transmitting power across distances, the work of Nobuyuki Kaya in Japan. More recently Paul Jaffe at the Naval Research Lab has focused on well-defined applications, military scenarios like providing power to far off outposts to reduce fuel convoys along dangerous supply lines. All of this boils down to that measure – the cost per pound (or kilogram). There is no lack of keeping track of this metric in the industry, not just for making concepts like space solar power possible, but for a world of such concepts also waiting for their day in the sun.

Costs per kg of different launchers. The Falcon Heavy has already staked a claim at a very low thousands of dollars per kg – about $1,100 per pound in its most reusable configuration. Updated from a version at NASA NTRS and The State of Play. Credit: Edgar Zapata,
Costs per kg of different launchers. The Falcon Heavy has already staked a claim at a very low thousands of dollars per kg – about $1,200 per pound ($2,647 per kg) in its most reusable configuration. Updated from a version at NASA NTRS and The State of Play. (Update September 30, 2021: This caption was corrected from $1,100 per pound to $1,200 per pound, the $2,647 per kg in the graph) Credit: Edgar Zapata,

Refueling, private stations, and more

In the decades since we envisioned what might be for SSP, there has been no lack of more construction ideas and travel destinations waiting in line for low fares. Pondering a cost per pound an obvious question became a pound of what? It turns out most of what might end up in orbit in order to go anywhere beyond is just propellant. By 2011 a team at NASA was looking at refueling in space. Once again as with SSP, if the fare for the ride was much lower to get to orbit, by then a distinct possibility from seeing where the SpaceX Falcon 9 was going, what might be possible with the Falcon Heavy on the drawing board? That task was undertaken by Charles Miller, NASA Senior Advisor for Commercial Space at the time, who ran with the possibilities. Many launch vehicles could compete to launch lighter, near empty spaceship stages, while other’s competed to load them up with propellant once in orbit. All this would make enormous sense at the lower prices per pound to low Earth orbit versus trying to get the mass up there all at once in any larger, so more unique, less flown and much more expensive launcher.

Miller and his team would report out on this (myself again included) – only not everyone was convinced. Refueling in space was immature some would argue, and (most often said) in either case NASA was already tasked by Congress to build a large rocket that could put up a large mass, propellant and payload, all at once. The task did not end well for the team. The numbers favoring refueling were compelling then, and they remain so, but the timing for such change was off.

Persisting, 2015 offered a repeat performance. Now Miller was outside NASA leading an independent look skipping the stop at a gas-station in space, now with “tanker” stages directly off-loading propellant to the customer. Here the gas station would come to you. The Evolvable Lunar Architecture study also included commercial lunar landers, perhaps two, perhaps one. All this would lead in phases to fully reusable landers refueling on the Moon from propellants mined and produced there. Using partnerships and going commercial, it would all add up, if the promising recent history for this NASA investment approach were repeated. There could be a permanent and growing presence on the Moon much sooner and for much less NASA budget than anything envisioned at the time.

To boot, the evolvable lunar architecture didn’t even need to de-orbit the ISS to free up funds to go to the Moon – a practical strength to the plan. The supply chain was strengthened along the way to the Moon rather than abandoning your rear at Earth orbit under guise of limited resources. To Miller it was “about a propellant economy in space” – only not everyone got it. Again, the numbers were compelling, and they remain so, but the timing for such change was off. Only now by not as much.

Fast forward to the middle of a global pandemic and awaken in 2021. If anyone had predicted such change they could be accused of wishful thinking. In April NASA’s Perseverance rover has extracted oxygen on Mars. From the barely-there carbon-dioxide atmosphere a small device called MOXIE has yanked out the oxygen and tossed aside the carbon in a process that might one day lead to refueling liquid oxygen on Mars. For refueling in space, NASA has awarded a contract to Eta Space to develop technology for the transfer of liquid oxygen. And atop all this, NASA has partnered with SpaceX to transfer 10 tons of liquid oxygen in space for Starships. If all this sounds eerily again like waiting for low fares for that trip that was otherwise unaffordable, it is. Except the low fares no longer seem far away. Forgotten in this, liquid oxygen is liquid oxygen, and liquid methane is liquid methane, even if everyone’s stages and what’s packed atop those remain unique and less amenable to becoming simpler commodities. The propellant remains most of the mass of getting anywhere, ready to take advantage of low costs per pound to orbit.

As well, all the refueling in orbit now seriously back on the NASA table comes after a touch and go moment in early 2020 where NASA did go commercial after all for its lunar lander. NASA’s eventual commercial lander selection (pending a final outcome on challenges from the losing bidders) was a reusable approach and the SpaceX Starship. The timing for refueling, reusable landers, and landers as partnerships for future commercial services was no longer off. The day had come.

The list goes on for what’s possible and the people who see the opportunities. As costs per pound drop, the commercialization of low Earth orbit is now on the table. This is also about more than just the launcher, as getting to low Earth orbit as the saying goes, is halfway to anywhere in the solar system. It is no coincidence that soon a private mission to space will use the Dragon spacecraft developed for NASA crew trips to the International Space Station. The Inspiration4 mission – “four crew members representing the mission pillars of leadership, hope, generosity and prosperity” – would arguably not be going to space were it not for a vehicle and a spacecraft the reliability, safety and price of which allow such a private mission. It helps these are not government owned or operated. Manufacturing can see a similar renaissance – as NASA’s Lynn Harper, lead of integrative studies for the Space Portal Partnerships Office at NASA’s, is fond of saying – as we discover “where gravity is holding back US industry”. Perhaps the breakthrough app for something made in space will be ultra-pure optical cable, ZBLAN at $2 million a kg, or it will be a crystal used for a cancer drug (like Keytruda). It could as likely be something unexpected, more valuable than we can guess.

Refueling, the commercialization of low Earth orbit, from private space stations, for tourism, manufacturing, science and research helping us live longer, healthier lives, and yes perhaps one day for space solar power are merely what we can imagine. The old model of build it and they will come may have been unambitious. In an era of thousands of Starlink satellites in orbit, what else might be on the table? Months ago, I had the rare opportunity to catch a recently launched fleet of Starlink satellites pass over the sky here in Orlando. A tidy row of bright lights streaming by on a clear evening from horizon to horizon leaves an impression. I wonder who might have dreamed a new dream on such an evening. For perspective, a completed Starlink constellation is of a mass of a multi-gigawatt Space Solar Power station – and it’s not waiting around for even lower costs on the ride and more often. This could all end up being an amazing picture of systems to get to space and systems and people in-space that make the old NASA chart, with X-33, Maglev and the laser-craft look all too linear. It’s enough to say that you don’t always get what you want, but if you try sometimes, you get what you need.

An observer will be tempted to seek a common thread in all of this. It could be how naturally innovative ideas are born then wait for that “what-if” of lower costs to get to Earth orbit. This is not a syndrome unique to the space industry, the ability to wonder what might be, say if a material were stronger or lighter, it’s manufacture cheaper. Our minds look ahead. What things we might do that day. The case for refueling in space, building power towers or private space stations, or for advances atop all that from near perfect fiber to life saving medicines to scientific knowledge, all depend on that cost metric. Yet getting to know many of the innovators here over many years, the real common thread seems elsewhere, in the perseverance of the champions of these possibilities before their time, without which the innovations wouldn’t be quite as ready when the affordable rides arrive.

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