Building a Spacefaring Civilization

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.

_______________________________________

 

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.

_______________________________________

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.

 

Index of Articles

  1. Opening the High Frontier
  2. Skyhook, a Journey to Orbit and Beyond
  3. In the Beginning . . .
  4. Why do Rockets Cost so Much?
  5. Combination Launch Systems
  6. It’s All About Speed!
  7. Visions of the Future
  8. The Call of an Unlimited Future
  9. Combination Launch Systems, part 2
  10. Outward Bound: Beyond Low Earth Orbit
  11. and someday . . . Starships!
  12. Mars: how to get there
  13. Outpost Space Stations
  14. Dreams of Space
  15. The Moon or Mars?
  16. Skyhooks and Space Elevators
  17. Stratolaunch and the X-15
  18. Starship Congress
  19. Making Spaceflight Affordable
  20. How a Combination Launch System Works
  21. Starship Conference 2017
  22. New Worlds Conference 2017
  23. Opening the High Frontier
  24. Building a Spacefaring Civilization
  25. Space Exploration and the Future

Other websites

Videos

 

Opening the High Frontier

Opening the High Frontier – When is it going to Happen?

When will we finally have orbital industries, space hotels, and spaceports where anyone can buy a ticket to the high frontier?

I grew up with the space program and these are questions I have asked myself many times over the years.  In 2018 it will be 50 years since Apollo 8 flew around the Moon and 46 years since anyone has gone further than low Earth orbit.

Compared to all the dreams of space that we have all read about and seen in movies, the last 45 years appear fairly boring by comparison.  Yet if viewed from a historical perspective our slow rate of progress is pretty much the norm.  After all, it took over 100 years after the discovery of the Americas before the Jamestown colony was founded on the east coast of North America.

The reason for the delay was the lack of a compelling economic reason to go there.  It lacked the weather for growing sugar and it lacked the gold and silver of Central and South America.  On top of that, it was far away, the cost was high, and the risk was great.  This is also why we stopped going to the Moon.  There was no compelling economic reason to go there, it was far away, the cost was high, and the risk was great.  Like it or not, this also applies to going to Mars or the asteroids.

Fortunately,  compelling economic reasons change with the cost of transportation.  An activity that produces a product that is worth $1,000/lb is not going to be profitable if it costs $10,000/lb to ship it.  Yet that same product will be very profitable if the shipping cost is reduced to $100/lb.  This is what a Combination Launch System makes possible.  It lowers the bar on what constitutes a compelling economic reason.

But transportation costs and compelling economic reasons are not the only issues.  Another concern is the buy-in cost, the amount of investment that is needed to start a project.  The larger the buy-in cost the more difficult it is to earn that money back.  In other words; a large buy-in cost requires a product that everyone is going to want and that has enough total profit in it to pay for the initial investment and then some.  If the projected total profit for the product is not enough to repay the buy-in cost, there will not be many people who will be willing to put up their money to start the project.

An example of this is the first transcontinental railroad.  The first steam locomotive was built in 1803.

It didn’t take long for the economic advantages of this new invention to be proven and for people to realize the incredible wealth that would be generated by building one that would cross a continent.  Yet it took over 65 years before the first transcontinental railroad was built.

A big part of the reason for that delay was the size of the buy-in cost.  It finally took the US government to fund the first one to get the ball rolling, but after that, the railroads took off on their own.

So how can this information be applied to assist in opening the high frontier?

Compelling Economic Reasons

There are 4 immediate compelling economic reasons for making spaceflight more affordable.

  1. to serve the existing launch market (commercial satellites, military satellites, NASA, and the International Space Station)
  2. to reduce the cost of the planned Outpost Space Station program
  3. space tourism
  4. zero-g manufacturing

After those have been addressed there are:

  1. return to the Moon for water, raw materials, and regolith for shielding
  2. asteroid mining for strategic materials for Earth and for additional raw materials for the zero-g industries in Earth orbit

Are these reasons enough?  While most pro-space people would say yes, it is the opinion of the people in charge of NASA, our leaders, and the people who have money to invest that count the most.

Buy-in Cost

The buy-in cost for building a combination launch system is a 200 km long non-rotating skyhook, a reusable Mach 6  X-15 style first stage, a reusable upper stage rocket, and a reusable spacecraft.  The only new technology on this list that hasn’t flown before is the non-rotating skyhook.  As a result, it might be necessary to fly a skyhook flight experiment on the International Space Station and dock some unmanned suborbital spacecraft at the lower end before starting to build the full-size 200 km long skyhook.

In dollar terms, the buy-in cost for all these items should be in the neighborhood of $2 billion assuming they are all built by commercial companies working on fixed price contracts.  Since all of these items will be profitable for the owner/operators, it should also be possible to build all of them as joint government/industry programs which will further reduce the buy-in cost.

Politics

Dealing with politics is probably the most difficult part of starting any space project as there are so many factions in the space community with so many different and opposing positions.  Considering how long these groups have been competing with each other, it is also unlikely that they can be enticed to finally start working together.  More likely, it will take someone in a leadership position at NASA, in the government, or someone who has the funds to make a decision to build it.

So what would entice someone to make such a decision?

The answer to that will most likely be a combination of both stick and carrot.  The carrot being all the economic advantages, the stick being the fear of someone else building it first.

The reason for that fear is that there is room for only one skyhook around a planet.  That is because the skyhook will be constantly changing its orbital altitude and its orbital eccentricity in the process of launching and receiving spacecraft at both the upper and lower ends of the skyhook.  This constant change of orbital altitude, position, and period would lead to a collision between multiple skyhooks.  This means that whoever builds the first one will end up controlling access to the high frontier.  Whoever does that will also establish the political and social standards for the spacefaring civilization that will come into being as the result of affordable access to space.  In addition, the wealth brought home by those space activities will make the country that controls the skyhook the wealthiest nation on the planet.  I suspect that the only way to keep the peace with this will be to build the skyhook as part of a multi-national program as was done with the International Space Station.  It won’t be an easy sell.

In Conclusion

Writing the book Opening the High Frontier, this blog, the video, the other websites [1] [2], and presenting this idea at conferences has been a very interesting experience.  The growing level of interest as shown by the increasing number of people who read these sites, buy the book, as well as the interest and comments at the conferences, is both enlightening and gratifying.  I have no doubt at this point that a combination launch system with non-rotating skyhook will be built someday.  The only remaining questions are who will do it, and when they will do it.  As to the when, I hope soon as I would dearly like to use it.  As to the who, that is anybody’s guess.  While I hope it is the United States that takes the lead in building this, I can’t help but notice in the website statistics that there are a growing number of people from all over the world who are reading about this.  I hadn’t realized just how much interest there is in the idea of building a spacefaring civilization by people from all around the world.  I hope all of you who read this will consider writing a letter to President Trump and tell him of your support for making this happen.  It can’t hurt and it just might help speed things up.

Ad Astra!

 

Index of Articles

  1. Opening the High Frontier
  2. Skyhook, a Journey to Orbit and Beyond
  3. In the Beginning . . .
  4. Why do Rockets Cost so Much?
  5. Combination Launch Systems
  6. It’s All About Speed!
  7. Visions of the Future
  8. The Call of an Unlimited Future
  9. Combination Launch Systems, part 2
  10. Outward Bound: Beyond Low Earth Orbit
  11. and someday . . . Starships!
  12. Mars: how to get there
  13. Outpost Space Stations
  14. Dreams of Space
  15. The Moon or Mars?
  16. Skyhooks and Space Elevators
  17. Stratolaunch and the X-15
  18. Starship Congress
  19. Making Spaceflight Affordable
  20. How a Combination Launch System Works
  21. Starship Conference 2017
  22. New Worlds Conference 2017
  23. Opening the High Frontier
  24. Building a Spacefaring Civilization
  25. Space Exploration and the Future

Other websites

Videos

New Worlds Conference, 2017

I just finished presenting the Combination Launch System concept at the New Worlds Conference in Austin Texas.  The conference was really fun with a lot of great presentations, some potentially world-changing ideas, and a lot of really wonderful people.

The Combination Launch System concept also received a tremendous amount of interest and questions as well as many very positive comments by some very important people as a result of that presentation.  My thanks to all who were there for your interest, questions, and comments.  It has been a lot of work to create and validate this concept, write the book and put together the presentations, so it is truly gratifying to see people understanding and getting the value of it.  I hope all of you will share this idea with everyone you know so that we can get it built.

The Combination Launch System concept is the real deal.  It can be affordably built with existing materials and technology, and it will open the high frontier for settlement and development to everyone who has the dream and desire to go there.  All that is missing is communicating the idea to enough people so that we can get it built.

The need for a Compelling Economic Reason

One statement that was repeated many times by the business people and venture capitalists at the New Worlds Conference was the need for a compelling economic reason to invest the money for building a more affordable launch system for any space activity.   No one is interested in financing a project of this magnitude without the ability to recoup that investment and make a profit.  As Robert Heinlein once said, “There is no free lunch.”

Sending people to Mars to build a settlement is not enough of a reason to justify that investment.  There needs to be something on Mars that will justify the risk and payback the cost.  Something like the gold rush that drew people to California in the 1850s.  The same applies to going to the Moon, the asteroids, or building a space colony.  There needs to be a compelling reason that is worth all the effort that can’t be obtained for a lower cost on Earth.

The Outpost Space Station

One possible justification for such an investment is when that investment will reduce the cost of an already planned project by more than the cost of the addition.  An example of this is the Outpost Space Station that NASA wants to assemble out near the Moon.  The cost of launching all the pieces of the Outpost Space Station into orbit, boosting them to escape velocity, and then placing them in orbit at either L1, L2, or around the Moon will be extremely expensive.  Sending crews, supplies, and spare parts to it will also be extremely expensive.  Building a Combination Launch System to help launch the pieces of the Outpost Space Station into orbit and to escape velocity, as well as for sending crews and supplies to it once it is in position near the Moon, will reduce the cost of the Outpost Space Station program by more than it will cost to build the Combination Launch System.  It is a win-win situation that justifies the investment to build the Combination Launch System and makes the Outpost Space Station much more affordable.  Also, since the Combination Launch System will make money for its owners, it will also be possible to build every component of the Combination Launch System as a joint government/industry project.  That will further reduce the cost of the program.

Think about that for a bit.  The Outpost Space Station with Combination Launch System could become the modern-day equivalent of the transcontinental railroad that connected the East Coast with the West Coast and everything in between.  Only, in this case, it will connect the Earth with low Earth orbit, lunar orbit, and the Earth-Moon Lagrange Points.  It will also allow affordable access to the lunar surface and near-Earth asteroids on a regular basis once the spacecraft for those missions are built.

In addition, the Combination Launch System will make Earth to orbit transportation so affordable that it will allow the commercial development of low Earth orbit with orbiting hotels for space tourism as well as orbiting industries for zero gravity manufacturing and spacecraft assembly.

It will be the true birth of a real spacefaring civilization.

Once this is all in place it will only be a matter of time before spaceships will be going to Mars and the asteroids.

Those spacecraft will be followed by space colonies in cislunar space and in orbit around Mars

And it all starts with a Combination Launch System.

We are that close.

 

Index of Articles

  1. Opening the High Frontier
  2. Skyhook, a Journey to Orbit and Beyond
  3. In the Beginning . . .
  4. Why do Rockets Cost so Much?
  5. Combination Launch Systems
  6. It’s All About Speed!
  7. Visions of the Future
  8. The Call of an Unlimited Future
  9. Combination Launch Systems, part 2
  10. Outward Bound: Beyond Low Earth Orbit
  11. and someday . . . Starships!
  12. Mars: how to get there
  13. Outpost Space Stations
  14. Dreams of Space
  15. The Moon or Mars?
  16. Skyhooks and Space Elevators
  17. Stratolaunch and the X-15
  18. Starship Congress
  19. Making Spaceflight Affordable
  20. How a Combination Launch System Works
  21. Starship Conference 2017
  22. New Worlds Conference 2017
  23. Opening the High Frontier
  24. Building a Spacefaring Civilization
  25. Space Exploration and the Future

Other websites

Videos

How a Combination Launch System Works

A combination launch system works by reducing the total speed a launch vehicle needs to achieve in order to reach low Earth orbit.  For a launch vehicle to reach low Earth orbit on its own without the assistance of a combination launch system, it needs to accelerate to a very high apparent velocity.  In addition to achieving the actual speed of low Earth orbit (7,800 m/s), it also needs additional speed to overcome the force of gravity that is working to pull it down as it boosts for orbit and even more speed for overcoming the aerodynamic drag that wants to slow it down.  There are also other issues that require additional speed to overcome but these are the three largest.  It is the total of all these speeds that are known as the apparent velocity, or the total speed required for orbit.  When all of these speeds are combined together, the total amount of speed required to reach low Earth orbit when launching due east from Cape Kennedy is approximately 9,100 m/s.  This is the total speed required for orbit.

For a launch vehicle to reach orbit and do it affordably it also needs to be single stage, completely reusable, and carry a large enough payload to make it all worthwhile.  Unfortunately, it is not possible to build such a launch vehicle with current technology.  The reason for this is the amount of propellant that it takes to get to low Earth orbit using chemical rocket motors.  Using the highest performance chemical rocket motors available, a Single Stage To Orbit launch vehicle would need to be 87% propellant when it leaves the launch pad.  That leaves only 13% for the launch vehicle and payload.  That is not enough to make a Single Stage To Orbit launch vehicle completely reusable and still carry enough payload to make the cost per pound to orbit mass market affordable.

The closest we have come to building such a launch vehicle was the partially reusable Two Stage To Orbit Space Shuttle.  It had a propellant fraction of 87.2%, an empty weight fraction of 12%, and a maximum payload fraction of 0.8% when flying to the International Space Station.  It was also significantly more expensive to fly than any expendable launch vehicle.

This is where the combination launch system with non-rotating skyhook comes in.  The first step of a combination launch system consists of either

an air-assisted launch

or a ground assisted launch.

A subsonic air-assisted launch using a carrier aircraft like Stratolaunch will reduce the total speed required for orbit by approximately 1,100 m/s.  A 600 MPH ground assisted launch from a mountain top will reduce the required speed for orbit by approximately 900 m/s.  An air-assisted launch will require the addition of wings to the launch vehicle.  This will increase the empty weight of the launch vehicle as well as the drag.  A ground assisted launch does not require this.  The end result is they are both about the same when it comes to reducing the total speed required for orbit.  Reducing the total speed required for orbit by 900 m/s will reduce the necessary propellant fraction from 87% to 84%.

If it is assumed that a fully reusable single stage launch vehicle requires an empty weight fraction of 15% to be built (3% more than the empty weight fraction of the Space Shuttle, or a 25% increase in empty weight), then either of these assisted launch concepts will make this kind of launch vehicle possible but the payload fraction will still be only 1%.

If it is assumed that a fully reusable single stage launch vehicle will reduce the cost to orbit by 90% compared to existing expendable launch vehicles, then this system will reduce the cost to orbit to approximately 1/10th of what it is today.

If this reduction to the propellant fraction is used to increase the payload fraction from 1% to 4% and the launch vehicle is left unchanged, then this system will reduce the cost to orbit to approximately 1/4th of what it is today.

Either approach will work, but neither of them by themselves will make spaceflight affordable to everyone.

Now add the non-rotating skyhook to the launch system.  One design for a mature non-rotating skyhook has an overall length of 2,200 km and a lower endpoint velocity of 80% of orbital velocity for its altitude.  This will reduce the total speed required for the launch vehicle by 1,560 m/s.  Combine this with the 900 m/s velocity reduction that comes with a ground assisted launch and the total speed required for flying to the lower end of the skyhook becomes 6,640 m/s.  If it is assumed that the same high-performance LOX/LH2 rocket motors are used, the required propellant fraction will drop from the original 87% to 77%.  If it is also assumed that the fully reusable Single Stage To Skyhook launch vehicle can be built with an empty weight fraction of 15%, the payload fraction becomes 8%.  This is 10 times the payload fraction of the Space Shuttle when it flew to the International Space Station.  Now, keep in mind that this launch vehicle is a fully reusable Single Stage To Skyhook vehicle that is expected to cost 1/10th the amount to fly as any expendable launch vehicle and combine this number with the 10 fold increase in payload.  That works out to 1/10th divided by 10 = 1/100th the cost in dollars per pound to orbit of any expendable launch vehicle flying to orbit without the assistance of a combination launch system.  In other words, if the original expendable launch vehicle cost $10,000 per pound to orbit, the fully reusable Single Stage To Skyhook vehicle will cost somewhere in the neighborhood of $100 per pound.

If an empty weight fraction of 15% is not enough to build a fully reusable Single Stage To Skyhook launch vehicle, increase the empty weight fraction to 18%.  That is 50% more than the empty weight fraction of the Space Shuttle.  This will reduce the payload fraction to 5% and increase the cost of flying to the skyhook to $160 per pound.  To get back to the $100 per pound launch cost it will be necessary to increase the length of the skyhook until the lower endpoint velocity is moving at 73% or orbital velocity for its altitude.  This will reduce the propellant fraction of the launch vehicle to 74% and increase the payload fraction back to 8%.

This $100 per pound launch cost is what most people think of as affordable to everyone spaceflight.  Think about that.  If the seat weight per passenger is 200 pounds, that means the price for a ticket to the lower end of the skyhook will be in the neighborhood of $20,000.  How many people would buy a ticket to fly to the lower end of the skyhook for that price?  Would you?

What the view from the lower end of a skyhook will look like.

Impact on Lift-off Weight

Another issue that doesn’t get discussed very often is how the combination launch system and non-rotating skyhook affect the lift-off weight of the launch vehicle.  Existing launch vehicles are large and that adds to their cost.  The Space Shuttle had a lift-off weight of over 4.4 million pounds.  The Falcon 9 has a lift-off weight of over 1.2 million pounds.  The largest Delta launch vehicle has a lift-off weight of 1.6 million pounds.  By comparison, the Boeing 737 MAX airliner has a take-off weight of 195,000 pounds.  As the old saying goes, size matters, and it has a direct impact on cost.

What determines the lift-off weight of a launch vehicle is its payload fraction and the size of the payload that needs to be delivered.  If the design payload size for a conventional launch vehicle along the lines of the Atlas or the Delta is 12,000 pounds, and the payload fraction for the launch vehicle is 1%, then the lift off weight will be 1.2 million pounds.  If the design payload size for a fully reusable Single Stage To Skyhook launch vehicle using the previously mentioned ground accelerator and skyhook is also 12,000 pounds and it has a payload fraction of 8%, its lift off weight will be 150,000 pounds.  That is 1/8th the lift-off weight of the conventional expendable launch vehicle and on top of that, it is fully reusable.  It is also worth noting that its lift-off weight is less than the take-off weight of the Boeing 737 MAX.

Now notice the empty weight.  If the empty weight fraction is 15% its empty weight will be 22,500 lbs.  If the empty weight fraction is 18% its empty weight will be 27,000 lbs.  By comparison, the empty weight of the Space Shuttle Orbiter was 172,000 pounds.  Either way, imagine how much easier it will be to move the Single Stage To Skyhook vehicle around, to service it, and to prep it for flight.

When it comes to cost, smaller is definitely better.

What an air-launched fully reusable Single Stage To Skyhook launch vehicle might look like.

 

Index of Articles

  1. Opening the High Frontier
  2. Skyhook, a Journey to Orbit and Beyond
  3. In the Beginning . . .
  4. Why do Rockets Cost so Much?
  5. Combination Launch Systems
  6. It’s All About Speed!
  7. Visions of the Future
  8. The Call of an Unlimited Future
  9. Combination Launch Systems, part 2
  10. Outward Bound: Beyond Low Earth Orbit
  11. and someday . . . Starships!
  12. Mars: how to get there
  13. Outpost Space Stations
  14. Dreams of Space
  15. The Moon or Mars?
  16. Skyhooks and Space Elevators
  17. Stratolaunch and the X-15
  18. Starship Congress
  19. Making Spaceflight Affordable
  20. How a Combination Launch System Works
  21. Starship Conference 2017
  22. New Worlds Conference 2017
  23. Opening the High Frontier
  24. Building a Spacefaring Civilization
  25. Space Exploration and the Future

Other websites

Videos

Combination Launch Systems, Presentation

For those of you who live in or around Monterey, California, I will be giving a presentation on Combination Launch Systems at the Starship Congress  August 7-9, 2017, at the Hyatt Monterey Regency.

If you can make it, stop by even if only for an afternoon!  It will be great fun!

Eagle Sarmont

_______________________________________

August 18, 2017

The Starship Congress was great fun with lots of interesting ideas, projects, and people.  Unfortunately, no one presented a working prototype of either a warp drive or an anti-gravity drive, which means we are stuck with reusable rockets and combination launch systems for the forseeable future.

On the plus side, my presentation on Combination Launch Systems received rave reviews from just about everyone who saw it, both at the conference and on the live feed that was broadcast on the internet.  Here are two tweets that were forwarded to me as a result of that presentation.

It has not been easy to figure out how to communicate the combination launch system and non-rotating skyhook concepts to non-aerospace people due to both of these ideas being so different from other launch vehicle concepts.  It usually takes a good understanding of basic orbital mechanics and Tsiolkovsky’s rocket equation before the significance of these concepts becomes clear.  The high percentage of very favorable responses to this presentation tells me that I am finally on the right path for communicating that.  Even so, based on a couple of after conference comments, there were still at least two people at the conference who did not get the significance of what $100 per pound to orbit launch costs will mean to the opening of the high frontier for settlement and development.

Currently, it costs over $22,000 per pound to launch supplies and cargo to the International Space Station using the Falcon 9 rocket and unmanned Dragon spacecraft.  That number comes from the NASA/SpaceX Commercial Resupply Services contract that consists of NASA paying SpaceX $1.6 billion for 12 cargo resupply flights to the International Space Station.  That works out to $133.3 million per flight.  The maximum useful payload delivered by one of those flights was reported to be 2,708 kilograms or 5,970 pounds.  That comes out to $22,200 per pound of useful payload delivered.

Even if the $62 million per flight cost of flying a basic Falcon 9 rocket without the Dragon spacecraft is used, the cost of flying to the International Space Station would still be $10,300 per pound.

Now think of that cost in terms of your everyday activities such as the food you eat, the water you drink, and the air you breathe.

Now think of it in terms of the cost of launching the computer you are using to read this, of the cost of launching a spacesuit should you need to go on an EVA, and of the cost of launching a habitation module for you to stay in and work in while you are at the International Space Station.

Now think of that cost it in terms of building a spacecraft for going to the Moon, or building the pieces of a modular Moon Base that will need to be lifted into Earth orbit and then sent to Lunar orbit and finally soft landed on the Moon.  How many tons of materials will be needed in Earth orbit to do that?  Now multiply that figure by $10,000 per pound.

If you think $10,000 per pound to orbit is too much, use $5,000 per pound or $3,000 per pound, the total cost will still be way too much to allow us to start building a spacefaring civilization.

This is why we do not have a base on the Moon.  This is why we have not built a spaceship for going to Mars.  This is why we have not built space colonies or satellite solar power stations.  This is why we do not have space hotels and spaceplanes for carrying tourists into Earth orbit.

For someone to say that the cost of spaceflight is not the single most important issue limiting our activities in space tells me that that person does not understand the problem.

Yes, there are other issues that need to be solved such as closed loop life support systems, and how to deal with the long term effects of either reduced gravity or zero gravity.  There are also questions about how to protect astronauts from solar and cosmic radiation, and developing the technology for using lunar and asteroidal materials in order to live off the land, but solving all of these problems won’t matter if we can’t get the cost of getting off planet down to an amount that people can afford to pay.

In closing, I would like to say a special thanks to those of you who “liked” those two tweets.  The amount of work that has gone into developing and validating the combination launch system and non-rotating skyhook concepts has been huge and it is very gratifying to see people starting to see the value of them.

Thank you.

 

To read the conference paper “Combination Launch Systems” that went with my presentation, go here.

One last thing.  The people who put together the Starship Congress are currently processing the videos for all the presentations and will start uploading them to the internet as soon as they are completed.  I will include a link here to my presentation as soon as it is available.

Ad Astra

Skyhooks and Space Elevators

A skyhook is a proposed space transportation concept that will help make spaceflight affordable to everyone.  When used as part of a combination launch system it will make the building of a spacefaring civilization possible on a commercial basis.  There are two kinds of skyhooks, a rotating skyhook, and a non-rotating skyhook.

A non-rotating skyhook is a much shorter version of the Earth surface to geostationary orbit Space Elevator that does not reach down to the surface of the Earth.  It is much lighter in mass, can be affordably built with existing materials and technology, and in its mature form, is cost competitive with what is thought to be realistically achievable using a Space Elevator, assuming materials strong enough to build a Space Elevator ever become available.  It works by starting from a relatively low altitude orbit and hanging a cable down to just above the Earth’s atmosphere.  Since the lower end of the cable is moving at less than orbital velocity for its altitude, a launch vehicle flying to the bottom of the non-rotating skyhook can carry a larger payload than it could otherwise carry to orbit.  When the non-rotating skyhook is long enough, Single Stage To Skyhook flight with a reusable launch vehicle becomes possible at a price that is affordable to just about anyone.

Another way to understand the non-rotating skyhook is to think of it as a momentum exchange device that consists of a space station in a higher altitude, higher energy, elliptical orbit, with a cable that hangs down to just above the atmosphere.  When a suborbital spacecraft coming up from the Earth docks at the lower end of the cable, it pulls the space station down into a slightly lower more circular orbit.  In effect, the space station gives up some of its energy to the arriving spacecraft so that the arriving suborbital spacecraft can stay in orbit instead of falling back to Earth.  When the spacecraft lets go of the lower end of the cable to return to Earth, it gives that energy back which allows the space station to return to a higher altitude, higher energy, more elliptical orbit.  The end result is that the energy that is exchanged between the non-rotating skyhook and the arriving spacecraft and then returned to the skyhook when the spacecraft departs, gets used over and over again every time a spacecraft makes a trip to the skyhook.  This exchange and reuse of energy reduces the amount of propellant the launch vehicle needs to carry which allows it to carry more payload.  Less propellant also makes for a smaller, lighter, and more affordable launch vehicle.  More payload means that the cost of the launch can be spread out over a larger amount of cargo.  Both of these changes reduce the cost per pound of getting to orbit.  When the skyhook cable is long enough, airliner like operations to space become possible at airliner like prices.

History

The idea for a non-rotating skyhook evolved from the idea of an orbital tower which was first proposed by Konstantin Tsiolkovsky back in 1895.  The orbital tower consists of a really tall tower that goes from the surface of the Earth all the way to geostationary orbit.  Its purpose was to provide an economical way of getting to orbit so that the human race could start building a spacefaring civilization.  The reason for wanting to build a spacefaring civilization was to avoid the projected collapse of our civilization at some time in the near future due to overpopulation.  A collapse that is considered by many to be inevitable if we remain a single planet species.  So why not use rockets?  Konstantin Tsiolkovsky knew about rockets.  After all, he is the person who first worked out the mathematics for using rockets to travel through space to other planets.  As a result of that work, he knew just how uneconomical chemical powered rockets are, which is why he wanted to find a better way of getting into orbit.   He got the idea for the orbital tower as a result of a trip to Paris, France where he saw the Eiffel Tower.  While he knew that such an orbital tower could not be built, he felt certain that the existence of a theoretical solution to the rocket problem would eventually lead to a real world solution that could be built.  He was right.

The idea of the orbital tower led to the creation of the space elevator concept, another idea that cannot be built.  That led to the idea of a rotating skyhook, a type of rotating space elevator that rotates in the plane of its orbit like a two spoke wheel rolling across the top of the atmosphere as it orbits the planet.  While this idea can be built with existing materials, it also has three very significant operational problems that have yet to be solved.

The first of these is the very short amount of time that is available for an arriving spacecraft to hook up with the end of the cable.  A rendezvous window that is literally only three to five seconds long.  This is what engineers and scientists like to call a “non-trivial problem.”

The second problem is maintaining the synchronization between the rotation rate of the skyhook with its orbital period.  Since the rotating skyhook is in an elliptical orbit, the rotation rate of the cable needs to be in sync with the amount of time it takes to orbit the Earth so that the lower end of the cable will be at the bottom of its swing when the rotating skyhook is at the low point of its elliptical orbit.  When a spacecraft docks with the lower end of the rotating skyhook at the low point of its orbit, it pulls the skyhook down into a lower orbit with a shorter orbital period.  Since the rotation rate of the cable does not change when the rendezvous occurs, the rotation rate of the rotating skyhook is now out of sync with the new orbit.  The rotating cable will need to be brought back into sync with the orbit before another spacecraft can use the system.  This is another non-trivial problem.

The third problem with the rotating skyhook has to do with how the release orbit of the spacecraft occurs one-half a rotation after a spacecraft docks with the cable at the bottom of its swing.  This linkage of the release orbit to the time of arrival causes a problem in that only a very small percentage of the release orbits will be pointed in the right direction for a spacecraft that is going to the Moon and beyond.  The only solution to this is to limit the departure speed of the spacecraft to a speed that will take it to a higher altitude orbit where the spacecraft will use its onboard propellant to circularize its orbit and wait until it is in the correct position to boost for its final destination.  This noticeably limits the usefulness and cost advantage of the rotating skyhook for manned spaceflights to the Moon and beyond.

It was the search for a workable solution to all these problems that led to the creation of the non-rotating skyhook.  A skyhook that can be affordably built and operated with existing materials and technology and that doesn’t have the problems of the rotating skyhook.

For more detailed information about what a non-rotating skyhook is and how it works, go here.

A 200-kilometer long basic Non-rotating Skyhook configured to receive a suborbital spacecraft coming up from the Earth.

 

Index of Articles

  1. Opening the High Frontier
  2. Skyhook, a Journey to Orbit and Beyond
  3. In the Beginning . . .
  4. Why do Rockets Cost so Much?
  5. Combination Launch Systems
  6. It’s All About Speed!
  7. Visions of the Future
  8. The Call of an Unlimited Future
  9. Combination Launch Systems, part 2
  10. Outward Bound: Beyond Low Earth Orbit
  11. and someday . . . Starships!
  12. Mars: how to get there
  13. Outpost Space Stations
  14. Dreams of Space
  15. The Moon or Mars?
  16. Skyhooks and Space Elevators
  17. Stratolaunch and the X-15
  18. Starship Congress
  19. Making Spaceflight Affordable
  20. How a Combination Launch System Works
  21. Starship Conference 2017
  22. New Worlds Conference 2017
  23. Opening the High Frontier
  24. Building a Spacefaring Civilization
  25. Space Exploration and the Future

Other websites

Videos

The Moon or Mars?

There have been a lot of articles in the news about either returning to the Moon or going to Mars of late.  I think they are great.  Either destination is fine as long as we build the infrastructure that will make spaceflight affordable to everyone in the process.

My reasons for this are simple; whichever program we choose, I don’t want it to be canceled after a handful of missions due to excessive cost like the Apollo program was.  If we make spaceflight really affordable the program will continue and people will find a way to make money in space.  Once that happens we will be on our way towards building a spacefaring civilization and there will be no turning back.

Returning to the Moon or going to Mars without building the infrastructure to make spaceflight affordable will only result in another canceled program and another 40 to 50-year wait before we try again.  The reason for this is simple.  Currently, it costs over $12,000 per pound to go to the International Space Station.  You can check this yourself by going to the SpaceX website and looking up the cost of flying the Falcon 9 launch vehicle.  It is $62 million per flight.  If you look up the amount of useful payload that it can deliver to the International Space Station, the answer is 5,000 pounds.  $62 million divided by 5,000 equals $12,400 per pound.

Another example is the Space Launch System, NASA’s new heavy-lift rocket that is currently in the process of being developed.  The Block 1 version of this rocket is supposed to be able to lift 150,000 pounds into low Earth orbit.  The cost per flight is estimated to be $1.86 billion.  That also comes out to $12,400 per pound.

The Saturn V rocket that was used to go to the Moon in the 1960s would launch 3 astronauts and 140,000 kilograms into low Earth orbit for each Moon mission.  That is a little over 300,000 pounds or 100,000 pounds per astronaut.  100,000 times 12,400 equals $1.24 billion per astronaut in today’s dollars to go to the Moon.  You can be sure that sending an astronaut to Mars will cost more than that.  Even if the reusable first stage rocket technology that is being developed by SpaceX and Blue Origin is able to reduce the cost of getting into Earth orbit by half, the cost per astronaut for going to either the Moon or Mars will still be in excess of $600 million per person.  That is a lot of money.  So much money that no one has been able to come up with a commercial activity in space that can make enough money to justify the expense of manned spaceflight.

As much as I want to see us build a spacefaring civilization, it just isn’t going to happen with launch costs this high.  Anyone who tells you otherwise is either living in a fantasy world or expects to make money on it via government contracts.

So what can we do?

There are 3 things we need to do to make spaceflight affordable if we want to build a spacefaring civilization.

First, build a combination launch system that includes either an air-launched reusable first stage rocket for flying to the lower end of a non-rotating Skyhook or build a 600 MPH ground accelerator for launching a reusable first stage rocket to a non-rotating Skyhook.

Second, build a reusable spacecraft for launching from the upper end of the Skyhook for going either to the Moon or to Mars, as well as single stage reusable lander for the Moon or Mars.

Third, build outpost space stations with local sources of propellant for refueling those spacecraft and landers.

It doesn’t all have to be built at once.  It can be built a piece at a time with jointly funded government/industry programs.  SpaceX and Blue Origin are working on reusable rockets.  Vulcan Inc. is developing the Stratolaunch carrier aircraft for air-launching launch vehicles.  Bigelow Aerospace is developing inflatable space stations.  NASA is building the Orion spacecraft for cis-lunar spaceflight and possibly for going to Mars.  And finally, the US Air Force is developing a Maglev test track that could be used to accelerate a launch vehicle up to 600 MPH.

What else do we need?

Vulcan Inc. needs to develop a horizontal landing reusable first stage launch vehicle for its Stratolaunch carrier aircraft, and either NASA or Bigelow Aerospace needs to add a 200-kilometer long tether to the International Space Station or to a Bigelow space station along the lines of the one shown in this video.

Air-launching and the 200-kilometer long Skyhook will reduce the cost to orbit to 1/3 of what it is today, from $12,000 per pound to $4,000 per pound.  Making the air-launched first stage reusable should reduce the cost to $2,000 per pound.  Increase the length of the Skyhook to 380 kilometers and the cost will drop to $1,500 per pound.  Continue making the Skyhook longer and the price drops even more.  Once the Skyhook is long enough that the upper end is moving at close to Earth escape velocity it becomes possible to place an Orion spacecraft on a free-return orbit to the Moon without the need for an expendable upper stage.  Add a single stage reusable lunar lander and an outpost space station in lunar orbit and now we have an affordable transportation system for going to the Moon.

Before the Space Shuttle was retired we had the beginnings of a space tourism industry with people like Dennis Tito flying to the International Space Station.  The cost for such a flight was $20 million.  An air-launched reusable first stage launch vehicle flying to the lower end of a 380-kilometer long Skyhook equipped space station would cost 1/8th of that, or approximately $2.5 million.  Obviously, there will be more people wanting to go into space at that price than for what Dennis Tito paid.  Increased demand for flights will justify additional investment in the Skyhook to make it longer as a longer Skyhook will decrease the price even more.  Every time the price goes down the demand for flights will increase.  The increased demand will lead to further increases in the length of the Skyhook.  Eventually, it will reduce the cost of a ride to orbit to $20,000 per person.  That is what I call affordable to everyone spaceflight.

As the number of people in orbit increases, it will eventually become economically worthwhile to develop an off-planet source of consumables such as water and oxygen.  No matter how affordable the combination launch system becomes, it will always be more affordable to get basics such as water, oxygen, and shielding materials from either the Moon or an asteroid due to the lower energy requirements for going to those places.  Once we have access to those materials, building farm modules for growing food in space will also become worthwhile.

Having a NASA program for returning to the Moon or going to Mars will speed up the development of the combination launch system due to the increased demand for flights.  This will speed up the pace of development in commercial manned spaceflight as well as reduce the cost of the NASA program.  It is a win-win combination that will propel us into the solar system and kickstart the building of a spacefaring civilization.

We are that close to making it all happen.

Ad Astra

 

Index of Articles

  1. Opening the High Frontier
  2. Skyhook, a Journey to Orbit and Beyond
  3. In the Beginning . . .
  4. Why do Rockets Cost so Much?
  5. Combination Launch Systems
  6. It’s All About Speed!
  7. Visions of the Future
  8. The Call of an Unlimited Future
  9. Combination Launch Systems, part 2
  10. Outward Bound: Beyond Low Earth Orbit
  11. and someday . . . Starships!
  12. Mars: how to get there
  13. Outpost Space Stations
  14. Dreams of Space
  15. The Moon or Mars?
  16. Skyhooks and Space Elevators
  17. Stratolaunch and the X-15
  18. Starship Congress
  19. Making Spaceflight Affordable
  20. How a Combination Launch System Works
  21. Starship Conference 2017
  22. New Worlds Conference 2017
  23. Opening the High Frontier
  24. Building a Spacefaring Civilization
  25. Space Exploration and the Future

Other websites

Videos

Outpost Space Stations

The idea of using a network of outpost space stations (also known as deep space habitats) scattered around the solar system to assist in making manned spaceflight between the planets affordable has been around for at least 25 years.  Who came up with the idea originally I don’t know, but it is an idea that has its roots in the network of coaling stations that were built all around the world for refueling steamships back in the 1800s.  The steam engines that powered the early steamships were not very efficient and they burned a lot of coal.  So much coal that if a ship had to carry the coal for an entire voyage there wasn’t much room left for cargo to pay for the voyage.  To solve this problem coaling stations were built at strategic locations all around the world so that the steamships would only have to carry enough coal for the journey to the next station.  This reduced the steamship’s propellant fraction and increased its payload fraction, which reduced the cost of shipping people and cargo all around the world to an amount that just about anyone could afford.

This idea also applies to automobiles.  The average automobile only carries enough fuel to give it a range of about 300 miles.  Not a lot of range if you are planning a cross-country trip.  If it was necessary to design a car so that it could go across the country and back on a single tank of fuel, the car would be much larger and much more expensive to build, buy, and operate.  So much more expensive that very few people could afford them.  To solve this problem, a network of gas stations was built around the country.  It is the existence of this network of gas stations that allows automobiles to be so effective and affordable.  They decrease the car’s propellant fraction and increase its payload fraction.

This is what outpost space stations are about.  They are the refueling stations on the trade routes to the planets and asteroids.  They allow the spaceships traveling between the planets and asteroids around the solar system to only carry the propellant that is needed to travel to the next outpost space station along the route.  This reduces the amount of propellant the spaceship needs to carry and allows it to carry a much larger payload.  This reduces the cost of space travel to an amount that just about anyone can afford.

An example of this are the spaceships that were designed by Wernher von Braun for going to Mars in 1948.  These ships were designed for four major propulsive events: first, to accelerate from Earth orbit velocity to Mars transfer orbit velocity; second, to decelerate from Mars transfer orbit velocity to Mars orbit velocity; third, to accelerate from Mars orbit velocity to Earth transfer orbit velocity; and fourth, to decelerate from Earth transfer orbit velocity to Earth orbit velocity.  The total amount of change in velocity required for these four maneuvers is 11.48 kilometers per second.  The amount of propellant required to do this using the low-performance rocket motors of the day required that the spaceships be over 98 percent propellant when departing from Earth orbit.  This meant the empty weight of the spaceship, plus the weight of the crew and all their supplies and equipment had to be less than 2 percent of the departure mass.  In all of human history, no one has ever come close to building any type of vehicle with a propellant fraction that high and with an empty weight fraction that low.  Even if it were possible to build such a vehicle with existing technology, it would not be affordable on a commercial basis due to the extremely low payload fraction.

Now assume a non-rotating Skyhook in Earth orbit that has an upper endpoint velocity of just short of Earth escape velocity, an outpost space station at the Earth-Moon L2 Lagrange Point with a local source of propellant (either the Moon or a near-Earth asteroid that has been moved to L2), and a non-rotating Skyhook in Mars orbit that has an upper endpoint velocity of just short of Mars escape velocity as well as a local source of propellant (either Mars or one of the Martian moons), and look at what happens to the change in velocity requirement and the propellant fraction of an Earth-Mars spaceship.

Passengers and cargo bound for Mars, fly to the lower end of the Skyhook that is in Earth orbit using the fully reusable combination launch system described in previous posts.  From there they transfer to the upper end of the Skyhook where they transfer to the spaceship that will take them to the outpost space station at the Earth-Moon L2 Lagrange Point where they board the Earth-Mars spaceship.

On the day of departure, the Earth-Mars spaceship leaves the halo orbit at L2 and heads toward Earth where it will perform a gravitational slingshot maneuver as it accelerates to Mars transfer orbit velocity.  The change in velocity for these two maneuvers is approximately 1,500 meters per second.  When the Earth-Mars spaceship gets to Mars it slows down to just under Mars escape velocity and enters a high Mars orbit.  The change in velocity required for this maneuver is approximately 900 meters per second.  The total change in velocity required for this voyage is 2.4 kilometers per second.  That is 1/5th the amount of change in velocity required by the spaceships used in Wernher von Braun’s original Mars fleet.  This difference is due to both the Skyhooks and the outpost space stations with local sources of propellant at both Earth and Mars.

The transfer of passengers and cargo from the Earth-Mars spaceship to Mars will be performed by smaller spacecraft operating from the upper end of the Martian Skyhook using locally supplied propellant.  These spacecraft will also be used to carry locally supplied propellant to the Earth-Mars spaceship for its return trip to Earth.  If it is assumed that the Earth-Mars spaceship uses existing LOX/LH2 chemical rocket motors with oversized expansion nozzles (a specific impulse of 480 seconds), the propellant fraction for the journey to Mars will be 40 percent.  This will leave plenty of room in the mass budget for the Earth-Mars spaceship to make it completely reusable (no drop-off propellant tanks or stages), allow for a spinning section with artificial gravity for the crew and passengers, a hydroponics garden for fresh vegetables, plus plenty of radiation shielding.  If it is assumed that the empty weight fraction for this Earth-Mars spaceship is 40 percent of the departure mass, that will leave 20 percent for the payload.

If a nuclear thermal rocket motor that uses water for reaction mass is used for the propulsion system for the Earth-Mars spaceship, the propellant fraction for the trip to Mars drops to 25 percent and the payload fraction increases to 35 percent.  When used with a combination launch system that includes an escape velocity capable Skyhook, either of these Earth-Mars spaceships would make a trip to Mars mass market affordable on a commercial basis and would operate at a profit for the owners.

Either of these spaceships would also be capable of making trips to the asteroid belt, and to dwarf planets like Ceres, both affordable and possible.  Put an outpost space station in orbit around Ceres with a reusable lander that has the ability to lift water from the surface of Ceres into orbit, and these spaceships would have the ability to take a manned expedition to the moons of Jupiter and to explore the Greek and Trojan asteroids.

As hard as this might be to believe, we really are on the cusp of another Great Age of Exploration.  Only this time, instead of exploring a single planet, we will have people exploring the entire solar system.  All that is required is a combination launch system with a Skyhook and a couple of outpost space stations.  It truly is the beginning of our reaching out to the stars.

 

Index of Articles

  1. Opening the High Frontier
  2. Skyhook, a Journey to Orbit and Beyond
  3. In the Beginning . . .
  4. Why do Rockets Cost so Much?
  5. Combination Launch Systems
  6. It’s All About Speed!
  7. Visions of the Future
  8. The Call of an Unlimited Future
  9. Combination Launch Systems, part 2
  10. Outward Bound: Beyond Low Earth Orbit
  11. and someday . . . Starships!
  12. Mars: how to get there
  13. Outpost Space Stations
  14. Dreams of Space
  15. The Moon or Mars?
  16. Skyhooks and Space Elevators
  17. Stratolaunch and the X-15
  18. Starship Congress
  19. Making Spaceflight Affordable
  20. How a Combination Launch System Works
  21. Starship Conference 2017
  22. New Worlds Conference 2017
  23. Opening the High Frontier
  24. Building a Spacefaring Civilization
  25. Space Exploration and the Future

Other websites

Videos

Mars: how to get there

The first technically feasible idea for going to Mars was proposed by Wernher von Braun over 65 years ago.  It consisted of a fleet of 10 chemical rocket powered spaceships that were to be assembled in Earth orbit.  Total crew size for the fleet was 70 people.

mars-project-1

the-mars-project

slideshow01

It was an incredible vision.

Total planned Earth orbit departure mass for the fleet was 37,200 metric tons.  That is 90 times the mass of the International Space Station that currently orbits the Earth.  It was also a use once fleet.

Obviously, cost was a very significant issue.

So people began looking for ways to reduce the cost to something that was actually affordable.

One of the first follow-on proposals was the solar electric Sun Ship.

This was followed by the nuclear electric Umbrella Ship.

After that came the nuclear electric Mars Ion Rocket.

All of these were significant improvements over von Braun’s original proposal, but they were still too expensive.

There have been many others.

 

Back in the late 1950’s and early 1960’s, “Project Orion” studied the idea of using nuclear pulse propulsion.  This was a concept that used small nuclear bombs and a pusher plate to accelerate a spacecraft.  It was a great idea in that it offered both high thrust and high performance.  Unfortunately, it also meant mass producing thousands of small easily transported nuclear bombs.

 

Nuclear thermal powered rockets are another type of spacecraft that have been considered for going to Mars.

 

Variable thrust ion rockets, otherwise known as VASIMR (Variable Specific Impulse Magnetoplasma Rocket), are another.

They all work.  They all have advantages and disadvantages.  Unfortunately, none of them are affordable enough to make large scale colonization or trips by private individuals possible.

So what is the answer?

A big part of the problem is that all of these spacecraft have to carry the propellant and supplies for a round trip.  Afterall, there are no gas stations and grocery stores in space.  This leads us to the ideas of outpost space stations, local sources of propellant, prepositioned supplies, and cycler spacecraft.

 

Index of Articles

  1. Opening the High Frontier
  2. Skyhook, a Journey to Orbit and Beyond
  3. In the Beginning . . .
  4. Why do Rockets Cost so Much?
  5. Combination Launch Systems
  6. It’s All About Speed!
  7. Visions of the Future
  8. The Call of an Unlimited Future
  9. Combination Launch Systems, part 2
  10. Outward Bound: Beyond Low Earth Orbit
  11. and someday . . . Starships!
  12. Mars: how to get there
  13. Outpost Space Stations
  14. Dreams of Space
  15. The Moon or Mars?
  16. Skyhooks and Space Elevators
  17. Stratolaunch and the X-15
  18. Starship Congress
  19. Making Spaceflight Affordable
  20. How a Combination Launch System Works
  21. Starship Conference 2017
  22. New Worlds Conference 2017
  23. Opening the High Frontier
  24. Building a Spacefaring Civilization
  25. Space Exploration and the Future

Other websites

Videos