July 2018 - Opening the High Frontier

Space, the final frontier.

Today, it is a place of dreams.

Tomorrow, it will be the place of our future.

There have been many visions of our future in space. Visions that include manned spacecraft exploring the solar system,

asteroid mining,

cities on other worlds,

space colonies,

and someday, starships.

In short, space is a place of endless possibilities, endless opportunities, endless wealth, endless dreams, and the place where we will build a spacefaring civilization that will someday spread to the stars.

Some people see our move into space as an option. Others see it as a necessity. Jeff Bezos recently said,

“We must lower the cost of access to space to do these grand things that we’re talking about. This is not something we can choose to do. This is something we must do.”

He is not the first person to say this. The number of people who have made similar statements is too long to list. The collective message is clear. We are in the process of outgrowing our home planet and it is time for us to learn to live and fly in a larger universe if we are to survive.

So why haven’t we done this?

The answer to that is cost.

Today, even with the reusable rockets that are being built by SpaceX and others, the cost of spaceflight is still too high to make building a spacefaring civilization possible. To create that reality we will need to be able to launch thousands of tons and thousands of people into space for a tiny fraction of what we pay today.

That is what this blog is about. How spaceflight can be made affordable to everyone so that we can finally start building that spacefaring civilization.

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The idea of multistage rockets, space travel, and building a spacefaring civilization got its start in the late 1800s when Russian mathematician Konstantin Tsiolkovsky derived the rocket equation. This is the equation that calculates how much propellant a rocket needs to carry to reach a certain speed. This equation is at the heart of everything we do with space travel. It is this equation that explains why spaceflight is so expensive and why we have not been able to start building a spacefaring civilization.

An example of this is the Space Shuttle.

The Space Shuttle had a take-off weight of 5 million pounds. Its maximum payload to low Earth orbit was 50,000 pounds. The reason it had a take-off weight 100 times the size of its payload was the amount of propellant it needed to reach the speed of low Earth orbit.

In order for the Space Shuttle to fly to the International Space Station, it had to go even faster. As a result, it could only carry 25,000 pounds of payload there. This means that for a trip to the International Space Station, the Space Shuttle required a take-off weight that was 200 times the weight of the payload.

Now, let’s take a look at what this high propellant fraction did to the cost.

The total cost to fly the Space Shuttle was $1.5 billion dollars per flight. Breaking that down to dollars per pound of useful payload, the Space Shuttle cost $30,000 dollars per pound to low Earth orbit, and $60,000 per pound when flying to the International Space Station.

Obviously, not very affordable.

There are two reasons for this. First, is the amount of propellant that is required to reach the speed of orbit. Second, is the small amount of useful payload delivered compared to the overall size and cost of the launch vehicle.

This is a problem that exists for all past, and currently existing launch vehicles.

One example of this is the Titan 2 launch vehicle that was used to launch the Gemini spacecraft into low Earth orbit back in the 1960s.

It had a takeoff weight of 331,000 pounds and a gross payload to low Earth orbit of 7,900 pounds. If it had been used as a cargo carrier for hauling freight to a low Earth orbit space station like Skylab, its estimated useful payload capacity would have been in the neighborhood of 2,700 pounds. That is a take-off weight to payload weight ratio of 120:1.

Another example is the Saturn 1B with Apollo spacecraft.

It had a take-off weight of 1.3 million pounds and a gross payload capacity of 44,000 pounds when flying to the Skylab space station. The Apollo spacecraft had a launch weight of 32,000 pounds, which left 12,000 pounds for useful payload. That is a take-off weight to payload weight ratio of 108:1.

A more modern example of this is the Falcon 9 rocket with Dragon spacecraft.

The Falcon 9 with Dragon has a take-off weight of 1.2 million pounds. It can deliver 6,000 pounds of useful payload to the International Space Station. Like the Space Shuttle, it has a take-off weight to payload weight ratio of 200:1 for this mission. Its cost per flight, including the cost of flying the Dragon, is approximately $120 million dollars. That results in a cost of $20,000 dollars per pound delivered to the International Space Station. That is 1/3rd of what the Space Shuttle cost.

The last example is the Falcon Heavy launch vehicle with Dragon spacecraft.

This vehicle has a take-off weight of 3.1 million pounds and should be able to deliver approximately 16,500 pounds of useful payload to the International Space Station when both boosters and the core stage are recovered. That is a take-off weight to payload weight ratio of 188:1. Assuming that the Falcon Heavy with Dragon spacecraft costs $120 million dollars per flight when the boosters and core stage are recovered, the cost per pound to the International Space Station drops to approximately $7,000 dollars per pound. That is approximately 1/8th of what the Space Shuttle cost.

Both the Falcon 9 and the Falcon Heavy reduce the cost of getting to orbit by making as much of the rocket reusable as possible, and by simplifying the design so it is less expensive to build, fly, and maintain. Unfortunately, neither of these launch vehicles has been able to reduce the amount of propellant that is required to reach the speed of orbit. Just like the Space Shuttle, both the Falcon 9 and the Falcon Heavy have a take-off weight to payload weight ratio of approximately 200:1 when flying to the International Space Station. This places a limit on how much cost reduction can be achieved by simplifying the design and making the first stages of the vehicle reusable. So, while both of these vehicles are a wonderful improvement over the Space Shuttle, neither of them is low enough in cost to allow us to start building a spacefaring civilization. For that to happen the cost to orbit will need to drop to a few pennies on the dollar of what the Falcon Heavy costs. That just isn’t going to be possible using launch vehicles that have take-off weight to payload weight ratios this high. In order to get the cost down low enough to build a spacefaring civilization, we need to rethink how we get into space.

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Back in the early-mid 1800s, steamships had a similar problem to today’s launch vehicles. The steam engines of the day burned so much coal that the ships were limited in how far they could travel and still have enough room left over to carry a worthwhile amount of cargo. They solved this problem by breaking up the longer shipping routes into shorter lengths with strategically placed coaling stations. This allowed the early steamships to travel the globe while carrying a lot less coal and a lot more cargo. This significantly reduced the cost of shipping goods and people around the world while allowing the shipping companies to operate at a higher profit margin. It was a win-win solution for everyone.

In the case of Earth to orbit spaceflight, the problem isn’t distance traveled, the problem is the amount of speed the rocket needs to achieve to reach orbit. Since it isn’t possible to place a refueling station halfway up, the only other option is to reduce the amount of speed the launch vehicle needs to achieve to reach orbit. This can be done by adding speed to the launch vehicle at both the beginning and the end of its flight to orbit using externally applied power. This will significantly reduce the amount of propellant the launch vehicle needs to carry, which will allow it to carry more payload.

This is what a Combination Launch System does.

A combination launch system adds velocity to the launch vehicle at the beginning of its flight to orbit using either a catapult,

or by air launching the launch vehicle from high in the atmosphere with a carrier aircraft.

The combination launch system also adds velocity to the launch vehicle at the end of the flight with a non-rotating skyhook.

The end result is that the launch vehicle only needs to carry the propellant for the increase in speed that occurs in the middle part of the flight. The total amount of speed supplied by a mature combination launch system represents up to 1/3 or more of the total speed required for reaching orbit. This reduces the take-off weight to payload weight ratio of the launch vehicle from 200:1 down to 20:1 or less.

This will also allow the launch vehicle to be built as a 100% reusable single-stage vehicle that is much smaller in size than existing launch vehicles.

For example, the Falcon 9, which carries 6,000 pounds of usable payload to the International Space Station, has a take-off weight of 1.2 million pounds. A launch vehicle that is flown as part of a mature combination launch system that has the same payload capacity will have a take-off weight of approximately 120,000 pounds.

An example of what such a vehicle might look like is the X-24C that was designed by Lockheed back in the 1970s.

(photo from fantastic-plastic.com)

In addition, due to its smaller size, lack of drop off components, and complete reusability, this launch vehicle will also be able to make up to 6 flights per day to the skyhook when the skyhook is in an equatorial orbit.

It is the total of these changes that will reduce the cost of getting to orbit down to an amount that anyone can afford. It is the total of these changes that will also allow us to finally start building orbiting hotels and orbital industries on a commercial basis.

But this is not all.

It takes more than affordable Earth to orbit transportation to build a spacefaring civilization. Many of the astronauts have described low Earth orbit as barely skimming the cloud tops. Others have described it as Earth’s doorstep.

To truly step out into the solar system and build a real spacefaring civilization, it will also be necessary to make Earth orbit to escape velocity spaceflight affordable to everyone. Fortunately, the upper end of the non-rotating skyhook makes this possible. Just like the lower end of the skyhook that moves at less than orbital velocity for its altitude, the upper end of the skyhook is moving faster than orbital velocity for its altitude. This allows a spacecraft that releases from the upper end of a suitably long skyhook to be given a boost to escape velocity without using any of its onboard propellant. This reduction in propellant will reduce the size and cost of a spaceship for traveling to the Moon, Mars, and the asteroids to an amount that just about anyone can afford to use. This is what will make Moon bases and cities on Mars both affordable and possible. This will also make asteroid mining possible. Once we have affordable access to lunar materials and the asteroids, building space colonies will also become possible.

In short, a combination launch system is like the transcontinental railroad that opened up the American West. Once it is built, it will open up the solar system for settlement and development and allow us to finally start building a real spacefaring civilization.

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Month: July 2018

Building a Spacefaring Civilization