Spaceships of the Imagination

If you’re reading this you were most likely a space kid. You spent your childhood looking up at the stars, memorizing facts about the planets, or frankly watching too much Star Trek. Many of us space kids followed this passion all the way to college; majoring in engineering, math, or computers. Some of us went even further. We realized that space isn’t just something we could appreciate from the outside- but something we could actually be a part of. We formed teams to build our own rockets and satellites. We joined clubs like the Students for the Exploration and Development of Space (SEDS). We danced our butts off at Yuri’s Night. Most importantly we found our fellow space geeks and shared our mutual dream. Eventually the space kids grow up. We graduate, move to a new city, and start our career. For most of us that’s enough. But even still some of us want to do more. Every April- that driven few of us flock to Colorado Springs for Space Symposium, the ultimate gathering of space kids. As a 29 year old space kid I thought it was finally time to give it a go. This is what I saw.

Professional Burning Man. Disneyland for Adults. I heard all these adjectives used to describe Symposium during my drive out from Denver and I believed none of them. This is Colorado Springs we’re talking about. The place I used to bum around with my USAFA buddy during our misspent early 20s. Eating white person spicy Mongolian BBQ in the shadow of NORAD, meth houses, and gem stores. So consider my socks were firmly blown off as we drove up to this regal hotel, the Broadmoor, towering over the foothills like Cinderella’s castle over the Magic Kingdom.

Disneyland for adults is short selling it. The Broadmoor is far far nicer. Like if Walt Disney teamed up with the craftsmen who decorated the Titanic. The Broadmoor hotel or “campus” as Symposium regulars call it, surrounds a shallow lagoon. All the buildings are decorated with 100 year old art and pictures of the Hollywood royalty and actual royalty who have all stayed here. The glasses of wine all cost over $20, the food is exquisite, and you can order cigars at the hotel bar. This posh atmosphere at one of America’s most elite resorts gets to the heart of what Symposium is all about; a place for industry insiders to meet face to face and cut some deals.

The Broadmoor has been home to every Symposium since the first one back in 1984. Originally called the National Space Symposium, the event began as a forum for military space leaders to meet with their contractors in a kind of industry retreat. Over the decades the gathering gained a more civil, commercial, and increasingly international flavor so the “National” part was dropped. It soon outgrew the original Broadmoor hotel. A major defense contractor built an entire building on campus just for Symposium and even that got ultimately maxed out; the 2024 Symposium spilling over to the nearby Cheyanne Mountain Resort. Despite being the epicenter of all things space, Symposium’s military roots are still visible in all the uniformed Army, Navy, Air Force, Space Force, and allied attendees milling about.

Every military, civil, international, and commercial space organization you can think of sets up shop and holds court here. Some have large booths on the exhibition floor, others their own suite in the hotel, others yet rent out entire villas next door. Some of them are open for attendees to wander into, the vast majority are invitation only. These closed door meetings is where the real business of Symposium happens. For the rest of us there’s an exhibit hall, a speaker series, and the hotel bar. The exhibit hall is a good hour or so of fun. You can go to the speaking events but Jeff Foust will be live tweeting it faster than you can register what is being said. The hotel bar is where it’s at.

Imagine every cool space person you can think of. Every Brookie, every guest on Main Engine Cutoff, every person narrating the NASA livestream. They’re sitting in a bar and you can just go up and talk to them. And talk we did! Everything from nuclear thermal rockets to Netflix. It was one of the few times in my professional life I entered a room of relative strangers and walked out with new friends. But the best moments were reconnecting with people I hadn’t seen in years. Friends from past jobs, from college. People who I had risen up through the ranks of space dorkdom with. A lot had happened since those days- new jobs, new partners, a pandemic, but we hit it off just like old times.

Oh did I forget to mention that there are parties? There’s an official Symposium every night, each with a different theme. First night is always a chill cocktail reception. This year’s was sponsored by the Canadian Space Agency. Second night is always casino night. People put on their tuxedos and try their hand at winning some fake money. But the third night is always the main event, the party circuit. Look I’m a queer weirdo from Seattle so I’m no stranger to big parties. I’ve seen my share of underground theater kid parties, furry raves, and karaoke nights. So believe me when I say that space people by far go harder than anyone else.

The bacchanal began at 5 PM, precisely as the last meetings wrapped up. My first stop was a private house party in one of the villas. It was invitation only and my friend hooked me up. The wine and conversation flowed as we watched the sun set behind Cheyanne Mountain. Absolutely magical. That party wrapped up by 7 and the gang headed across the street to party number two, the Boeing mansion. By now it was proper dark and Boeing had set out a series of camp fires to gather round with spiked hot chocolate. It was cozy but we didn’t stay long-realizing that it would probably be a good idea to eat some food. We dined at the Golden Bee, a Broadmoor institution. Built from the hull of a 19^th century British schooner, the Bee was shipped panel by panel to the Broadmoor in the 60s. Tradition is that you’re supposed to throw a little felt bee at your friends upon entering the bar. Over the years various space companies have put their own spin on this and the bees were riding little Dream Chaser’s that night. After dinner (and who knows how many more drinks) we checked out the Lockheed Martin rave, REDACTED. A pretty good cover band was playing and I joined my buddies in the middle of the dance floor. As I stood there belching out I Wanna Dance With Somebody like I was at a gay wedding- I looked to my friends old and new and was just overcome with joy. Here we were, space kids all grown up dancing the night away. Whatever cosmic destiny awaits humanity- a base on the Moon, cities on Mars, finding life beyond Earth- it will be because of the people in this room. But for now that was all put aside. The night was young, the music was pumping, and we were standing atop the world.

I’ve been doing some thinking after writing How Cheap Can Rockets Get a lot of thinking. If you recall, my big conclusion was that although there is the potential for rockets to get orders of magnitude cheaper, they would still be an expensive means of transportation by terrestrial standards. Likely too expensive to do any of the interesting use cases we have in mind. There had to be a better way.

This led me down the fascinating rabbit hole of non-rocket space launch. Many of these ideas like space elevators and launch loops are really just napkin sketches. We don’t even know if some of them are possible. A set of concepts that seem quite feasible is to use electricity to launch things into space. People have proposed things like electromagnetic catapults, lasers, or even spinning rotors. All extrapolations of tech we have today but it turns out that they don’t really scale that well. It turns out that rockets are incredibly efficient heat engines. You’ve probably heard the statistic that a single Space Shuttle main engine produces the power output of 7 Hoover damns! That means it would probably require building the U.S. electrical generation infrastructure several times over to support the kind of launch cadence and tonnage we have today!

There is one idea for non-rocket space launch that feels just about ready for prime time – space planes. Space planes are an old dream. German rocket pioneer Max Valier was vociferously advocating for them back when Werner von Braun was still an undergrad. To Valier, space travel should be a natural evolution of high speed air travel, a philosophy espoused by many a space plane proponent. He imagined a vehicle that could operate out of any airport, fly to space under its own power, and return to a runway like any other aircraft.

 Rockets became the dominant form of space launch, but work on space planes never stopped! I could go on and on about Eugen Sanger, BOMARC, HOTOL, & the X-30. Heck a we technically did fly the Shuttle, more of a rocket boosted glider, but at least got the runway landing part down!

The hard part about spaceplanes has always been the propulsion. Most concepts utilize a combined cycle engine. Such an engine would start in an airbreathing mode, using Earth’s atmosphere as a source of propellant, just like a jet. It would then switch to a pure rocket engine at the edge of the space and continue to orbit like any other launch vehicle. By using the atmosphere as propellant, a combined cycle engine would be orders of magnitude more efficient than a conventional rocket. So efficient that the spaceplane could reach orbit on a single stage, a true airplane to space.

Combined cycle engine technology is really hard to do, with engineers comparing to the challenge of keeping a match lit in a hurricane. However there has been explosive progress in hypersonic vehicles over the past 10-15 years, most of it funded by the military. Many of the underlying challenges are being addressed and it has even been rumored that such a combined cycle engine is already flying. I feel somewhat comfortable saying that spaceplanes are no longer an if but a when.

If you remember from our previous chat on rockets, we looked at two types of launch vehicles. An expendable/partially reusable medium lift rocket called Enterprise 8 and a fully reusable heavy lift rocket called Battlestar. Remember how the cost of launching these vehicles is dependent on three things: the infrastructure cost of running your space company, the production cost of building new vehicles and stages, and the propellant cost of fueling up your vehicle. Further recall how as the number of launches increases the cost per launch tends to be dominated by the cost of propellant and the cost of building expendable hardware. Eventually the economics are mostly driven by the cost of fuel. The rocket can only get so cheap.

Let’s add a spaceplane to this, we’ll call it Fireball. Fireball like other proposed spaceplane concepts would be a single stage to orbit vehicle, probably powered by hydrogen and oxygen. Fireball can deliver about 15,000 kg to orbit then return to a runway to be used over and over again. Fireball’s greatest advantage is that it can fly out of any commercial airport. Not needing to support launch pads or integration facilities results in orders of magnitude lower infrastructure cost than a rocket. For this analysis let’s say it’s about a 100x reduction.

The results are below and to be honest I was a bit surprised. Fireball, a flappin SSTO spaceplane actually ends up being a slightly more expensive way of putting mass into orbit than Battlestar! Why is this?

Having lower infrastructure cost up front really helps Fireball initially compete with Battlestar. However as flight rate increases both system’s amortize their fixed infrastructure costs to functionally be zero and Battlestar’s large payload size quickly trumps Fireball’s initial advantage.

That said, given where the launch industry is today a vehicle like Fireball would be the lowest cost means to access space by far. There may be an age of spaceplanes yet but the window is closing. The U.S. alone is already launching over 100x rockets a year out of the existing pads. Enough new pads are being built to easily double or quadruple that number.

I am particularly nostalgic for flying boats. They represent a lost golden era where air travel was a glamorous adventure. I think we may one day look back on spaceplane concepts in a similar way. Like flying boats were to the dawn of aviation, space planes were to the dawn of space travel. The obvious choice when the technology and infrastructure were immature. But as with flying boats technology and the world at large has surpassed the original vision. We may gain a future of mass space travel on giant rockets, but we may lose the dream of a spaceplane in every airport.

Seaplanes and flying boats are still around though. The arrival of the jet airliner did not fully end them. They have their niche and I think spaceplanes will too. There are all kinds of missions an SSTO spaceplane may be great at and they will absolutely have a role to play in our space future! Just not for the reasons you think.

One of my big hunches on how the world works is something I call the Human Information Machine. The idea is basically this: human society is functionally this big data network, the information machine, with each individual as this node of experience. Society adapts, innovates, and changes at the rate at which individual learning and experience permeate through the network.

We are all born knowing nothing. Everything from there on out has to be learned. Some of what we learn we acquire through our own direct experience. You touch a hot stove and in a visceral moment of pain learn to never do it again. Some you learn from your family and friends. You see your parents brushing their teeth and you copy. But unless you were born into a community of naval engineers, your parents can’t teach you how to build a nuclear submarine reactor. If you want to learn anything more than what you or the people around you can immediately experience you have to go read about the experiences of someone who did. The vast majority of what we know, we learn through language and culture, through the information machine.

I think that technological innovation is fundamentally the frontier of evolving individual experience. If you work with a new technology or innovation directly you gain firsthand experience with it. You “get it” in a way that people who do not have your experience cannot. In time others will “get it” as your experience is recorded and permeates throughout the larger network. An example I often think about is the almost 30 year lag between the fundamental discoveries of quantum mechanics at the beginning of the 20^th century and the development of nuclear weapons in the middle. In the early days, outside of some visionaries like H.G. Wells, you would have to be an advanced physicist to fully understand the implications of E = mc². It was a paradigm shift away from the previous 400 years or so of physics and it took a few decades for this knowledge to be digested by larger society and their military planners.

Being on the outside of this knowledge frontier does not relegate you to living in ignorance. You have experience to share as well. Your experience can provide additional context and this context synergistically creates new knowledge and discoveries that weren’t there before. I call this melding of experiences reprogramming and it is the conversation that drives the world.

The first generation of video games were effectively electronic gambling machines. Early game companies originally cut their teeth on pinball, pachinko, playing cards, and slot machines so everything in their experience indicated that arcade games were just going to be an electronic continuation of what they had been doing for decades. Over time people from outside the gambling industry worked their way into these organizations. They brought their experience from fields such as illustration and film, which they used to create things with the electronic game medium that simply could not be done with a pinball or slot machine. These second generation games brought about innovations like levels, narrative stories, and open worlds. It fundamentally reprogrammed our understanding of what a video game could be and the result has been the great art form of our time.

Video games, computers, nuclear energy, the internet, space travel, etc. Our society lauds the ideal of the lone visionary who steps in and reprograms the information machine in a new direction. This focus on the value of individual experience has gotten us very far but I feel that we often downplay the ways an individual reprogramming can go wrong. There is frankly a lot of junk data in the information machine. Assumed knowledge that either still exists out of ignorance or was deliberately put there with malicious intent.

We have created a few rudimentary error checking mechanisms; the scientific method, democracy, market economies, but the junk remains. Underpinning these systems is the philosophy that even the most intransient of people can be won over, reprogrammed to a different point of view, with a well-reasoned argument. But humanity is not a community of rational actors. We’re more like a series of storytelling animals with a strong internal narrative. Junk often stays in the system because people have constructed an entire identity around it. Changing your mind often means first admitting that you were wrong, something that we know is literally one of the hardest things for human beings to do.

My hope for the world is that we will see a reprogramming on reprogramming. I think that the era of hot takes, argument, and debate is over. The way forward is to reprogram the information machine on mutual respect, honest sharing of experiences, and a good faith desire to understand the truth, no matter how uncomfortable. Of not putting all our faith in the experience of a very talented individual but in the collective experience of very talented teams and societies. This big reprogramming is probably going to take a long time, frustratingly long, but I maintain a kind view of our civilization. This is literally the first time the information machine of this spaceship Earth has had to work through it. I remain optimistic that we are going to figure this out and that humanity will be around for a very long time.

How cheap can rockets get? It’s an important question to answer for grokking the future of humanity in space. Soon rockets will be as easy to fly as aircraft and costs are going to get so low that we’ll be flying to Mars as easily as we fly across the ocean. Right?

Let’s do a little thought experiment. Imagine a hypothetical launch vehicle, the Enterprise 8. Enterprise 8 is an expendable two stage vehicle and can put about 12,000 kg into LEO. It burns about 300,000 kg of liquid oxygen (LOx) and about 110,000 kg of kerosene (RP1). Generic early 2020s rocket.

The cost per kg to put stuff into space is roughly a function of 3 things. The first is the Infrastructure Cost, i.e. the cost of all the infrastructure on the ground to make our space launch operation work. This includes stuff like engineers, technicians, security guards, HR, custodians, and all the factories, launch sites, and recovery ships they work in. The second is the Hardware Cost, the cost of the Enterprise 8 itself. Lastly there is the Propellant Cost, the cost of the propellant that is burned every launch.

Let’s assume an annual Infrastructure cost of $750M/yr. I could explain how I came up with this number but it is a bit wonky, tedious, and best saved for an appendix, go check it out if you really feel like it. A rocket like Enterprise 8 is expected to have a booster cost of about $20M/unit and an upper stage cost of about $10M/unit. The government publishes the price of rocket fuel, so with that let’s get number crunchin.

First let’s look at the fully expendable version of Enterprise 8. Using the assumptions above we can plot $/kg as a function of flight rate, the # of times we launch Enterprise 8 per year.

The shape of this curve is important. See how costs start off super high when launch rate is low and then logarithmically decrease as flight rate increases? There is a saying in economics, given infinite time all fixed costs go to zero; the more we fly Enterprise 8 the better we can spread out the Infrastructure Cost. Fly often enough and the Infrastructure Cost contribution is functionally zero. At this point the cost to fly the rocket is effectively the marginal cost to build a new rocket and fuel it up. As long as Enterprise 8 consumes the same amount of fuel and remains expendable, $2500/kg is the best this vehicle ever gets.

Undeterred we task the boffins at our fictional launch company to modify Enterprise 8’s booster stage into being reusable. Let’s say we’re able to make a version that can be reused up to 20 times or so.

Reusing the booster knocks about 60% off the cost of the launch. This partially reusable Enterprise 8 can achieve about $1000/kg.  But why stop at only 20 reuses per booster, what if we did more?

Turns out it doesn’t really matter. I plotted the impact of # of reuses on the cost of the rocket.

More reuses never hurts, but each takes a smaller and smaller part of the cost away, and thus each additional reuse has less benefit to cost. With many reuses, the best best partially reusable Enterprise 8 can do is about ~$900/kg.

Mars in our sights we decide to go big or go home with a fully reusable launch vehicle, Battlestar. Battlestar is going to be a beast of a rocket. It can put about 100,000 kg of payload into orbit. It costs about $300M to build and can be reused thousands of times, just like an airliner. It requires about 4 million kg of LOx and 1 million kg of natural gas.

Holy moly, $17/kg! That’s a 98% cost reduction over Enterprise 8! By reusing both stages, Battlestar is able to reach a point where the marginal launch cost if basically the cost to fuel it up.

This is a number worth advertising. But it’s worth noting it takes about 2,000 flights a year to get to that point. If only 100 flights a year are launched, costs are still more like $500/kg. Still a 50% reduction over Enterprise 8.

Enterprise 8 and Battlestar are simplified approximations of vehicles like Falcon 9 and Starship but they serve to illustrate what is possible with chemical rockets. A 100x reduction in the cost of launch is totally possible and may even be unlocked with vehicles being built today. The day may soon come where we see rockets as just another mundane transportation system. For terrestrial logistics we tend to compare various modes of transport by their cost per ton mile. This is roughly correlated to the energy efficiency and hence the fuel consumption of the vehicle. How do rockets stack up?

To try and make this an apples to apples comparison we need a terrestrial benchmark to compare the rocket against. I am going to pick a totally arbitrary distance of 6000 km, about the difference from Europe to North America. The space community loves to make comparisons between space exploration and the European conquest of the Americas. It’s time to put our money where our collective mouths are and see if there’s any truth to this.

The table below puts rockets on a continuum with other transportation systems.

Mode of Transport	Cost ($/kg)
Ship-Transatlantic1	$0.13
Airplane-Transatlantic2	$7.00
Helicopter-Transatlantic	$17.00
Battlestar-LEO	$17.00
Battlestar-Lunar	$85.00
Battlestar-Mars	$153.00

1. Ship data from bureau of transportation statistics. ↩︎
2. Airplane & Helicopter data from Straightline Aviation ↩︎

So there you have it, using a vehicle like Battlestar to get to LEO is like trying to cross the ocean in a helicopter. Launching tankers to refuel Battlestar so it can go on to the Moon or Mars would be like sending a flotilla of helicopters to the east coast, using them to fill the tanks of a single helicopter in NYC, and flying that helicopter onward to California. Definitely more involved than the Mayflower.

If you want to get a feeling for what space infrastructure may look like, go look at a place where helicopters are effectively the only means of transportation. The list is not large; isolated mountain top basecamps and outposts. These are places where the high cost of helicopter transport is worth it because there’s just no other way to get material up there. These huts and bivouacs are modest. If you want to build on a mountaintop, most of your budget is still going to transport, not the building itself. Despite these constraints humanity has slowly established a presence at the top of the world. It’s nowhere near as big as European colonies in North America or even the bases of Antarctica, but it’s still home to hundreds of people living, working, and thriving in a hostile environment. There’s no reason space can’t be our next mountaintop.

Photos courtesy of SpaceX and Chamonix Mont-Blanc Hélicoptères

Appendix: How I Came Up With the Infrastructure Cost

Welcome, glad you made it down here. Good on you for wanting to know more. I got to the $750M number by shamelessly copying a methodology from Jonathan Goff. Selenian Boondocks is one of the great space blogs in its own right and is a huge inspiration for what I am trying to do with Spaceships. Anyhoo, Jon’s approach is to assume a headcount for our hypothetical launch company. For this post I assumed 2000 employees, about the size of Relativity Space or United Launch Alliance. Other space companies are larger but they have their fingers involved in many other things than launch. We’re going to assume that each employee carries a burdened cost of $250K/year. This represents their salary and benefits. Assume a further 50% in overhead to account for all the facilities and administrative roles.

$750M/yr is somewhat in the ballpark for large space transportation programs. Recent public statements from Elon Musk indicate that the Starship program has an annual cost of around $1B-$2B/year. This is for a very ambitious and fast paced R&D program. Typically engineering costs go down after the rocket is flying as development engineers are assigned to other programs, leaving behind a smaller pool of production and operations staff.