Sunday, April 21, 2013

HILLS Space Plane - David Luther Interview

Being recently introduced to the Horizontal In-Line Launch Staging (HILLS) Space Plane and finding it dramatically cool and futuristic, I ventured to seek an interview with David Luther.  David is the mastermind behind this impressive design.

HILLS Space Plane Design

David Luther,  You have a cool space plane concept can you give a brief description of it?

Two blended wing body aircraft are joined as a single space plane to fly from a runway to space and back.  They are joined in line, nose to tail for aerodynamic and safety advantages until they separate in flight for staging.  Their combined wings enhance lift with reduced drag for a smaller more efficient launch system that is fully reusable as well.

How did you come up with this idea?

Years ago I worked with Bill Colburn on a suborbital blended wing body concept.  These forms offer large internal volume and reduced drag.  One member of that effort suggested we consider orbital applications.  I proposed joining wing bodies in-line to keep the frontal area low.  The shuttle accidents validated placing the crew out in front of booster malfunctions as well.  Being able to stage early offers an escape path.

Is the in-line configuration a new idea or one just not implemented yet?

We see the X-43 on the nose of a Pegasus winged rocket in testing.  Other similar examples are usually lofted by a conventional jet aircraft.  I have never seen this done from the runway with a blended wing body though.  We see interesting aerodynamic effects from the two wings acting in harmony as a single wing.  This was the feature that we identified as a patent opportunity.

You have a mother ship and an orbiter.  How would this configuration make it to Earth orbit?

We are similar to other horizontal proposals of the past except for having stages in-line.  I like using a rail launch for control during takeoff.  Rubber tires threatened the Concorde and rocket fuel is a lot of responsibility for the pilot. Rails remove issues with traction in crosswinds and may be used for braking in an abort emergency.  Any energy gain is frosting.  Our models and drones will use a rail launch as most drones do.  Landing gear can be lighter when only tasked with a single empty stage, adding more payload capacity. 

Suborbital speeds are good in the lower atmosphere, and rockets can deliver the delta vee in thinner air where drag is less of an issue.  Blunt forms are better for reentry as most active shuttles show.  We are less blunt than some lifting bodies so we may retain some cross range flight ability on landing. 

Some say that wings are not needed in space, and that wings and such provide unnecessary weight to the vehicle.  Why is this a better system than using rocket and capsule?

True, to go to space is easy without wings, but to recover the booster and orbiter is important since they are  assets.  Low cost and high flight rates will require recovery of the total system.  Wings are also functional for glide recovery if propulsion fails on ascent or reentry.  Vertical landing lacks this alternative on propulsion loss, and they have the mass penalty of more fuel load. 

Capsules are fine, but I haven’t seen much reusability historically.  The X-37 is operating reusably on a regular basis with wings today.  Orbital Sciences Pegasus used wings to aid orbital ascent, Stratolauncher will build on this, and Xcor will offer an orbital system too.  We may just have a little of the mass and fuel burn towards this goal.

Blended wing bodies offer high lift and low drag with good internal volume.  When coupled we see the orbiter making a contribution to lift during the ascent flight.  The wings and associated vortex activity multiply the efficiency of the booster combination.  The booster can be smaller as it gains wing area from the orbiter.

This principle can offer smaller atmospheric airliners for ocean crossings too.  A booster can enable smaller engines and fuel tanks for atmospheric flights.  This also empowers greater efficiency for unmanned drone systems.  New propulsion like scramjets will need an efficient booster design as well.

HILLS Space Plane - Separation
Where are you in your project?

Kickstarter may fund a model airplane as a demonstration.  That would be a fun project, but we already have some interest from the drone market.  If these are on duty for crop monitoring and border patrol, the idea will become more common.  Production and visibility can open minds to more applications.  We are open to billionaire angels, but a regular paycheck is an acceptable alternative too.  Jeff Greason and Xcor are my role model in this area: “Show me the money!”

What do you hope to accomplish?

I want to eliminate the new American caste system called “unemployable”.  If you are part of that group, please consider donating time to our effort.  We will invest sweat equity towards a new paradigm: “If you can’t join them, lick them!” 

What do you need to accomplish it?

Faith and patience.  Some competitors will fall to overconfidence or system complexity and alternative solutions will gain more opportunities.  Some systems will arrive in the right place at the right time and grow with the opportunities. Some solutions are as natural as water flowing downhill; buy farms with good bottom land soil and plant!

HILLS Space Plane - Cut Out

What do you say to the other alternate ways to orbit like that of JP Aerospace (dirigibles to orbit), the Space Elevator guys, or even air launch companies like Orbital Sciences and Stratolaunch and Virgin Galactic?

I had lunch with John Powell (JP Aerospace) last year and we may want some light gas pockets in future space planes.  Helium is in short supply lately though.  Space elevators are focused only on the moon now, and other orbital efforts will only help to build a market.  We hope to show that market a way to shave a little waste from the system.

Alternative systems are good for niche applications as with rotary and fixed wing aircraft.  Heavy lift may favor vertical launch and passengers may favor wings.  Vertical landing is the only path to the moon and asteroids.  We need all the good ideas.

Is there anything else in particular you wish to share with aerospace aficionados?

Don’t waste your study hall time drawing pictures of space ships.  Do the math!!

David's HILLS Space Plane is a unique and awesome concept.  If David has his way and it's successful, we may be traveling to orbit effortlessly as passengers like we do international flights now.  It could be a Star Trek kind of experience.  To follow on what David said, drawing pictures is fine, but make them reality with math.  Science, Technology, Engineering, and Math (STEM) are where it's at.

[Pictures were provided courtesy of David Luther]