Experts

Experts

SKY RAMP TECHNOLOGY

      My name is Carlton Meyer and I serve as the editor and webmaster for the Sky Ramp website.  I am no space expert, I just have bachelor degrees in finance and data processing.  I spent a few years as an engineer officer in the US Marine Corps and have been editor of a military technology magazine for the past eight years where I've come in contact with hundreds of experts.  

       Watching vertical rockets "blast off" is fun, but always seemed wasteful as the vehicle slowly crawled upward while expending vast amounts of fuel.  One idea that stuck me as brilliant was to boost space vehicles off the ground.  Large space vehicles burn tremendous fuel just to get up to 100 mph.  Since rocket sleds at China Lake have propelled 130,000 lb. objects to Mach 4.4, the potential for an inclined rail to boost space vehicles is real.  

      Many experts liked the idea, and began to send me more information which became articles in my magazine.  Eventually, the information became so large that I decided to set up a section to promote the idea of ground-based assisted launch, also called ground accelerators, catapults, and sometimes mass drivers.  There is lively debate about the best method: rocket sled, jet sled, pneumatic, gravity, maglev, hydraulic, or a combination, yet all agree that any method of ground assist yields tremendous benefits.  There is also debate about maximum Gs, the best launch angle, practical track length, and top safe ground speed.  However, everyone agrees that "blast offs" are wasteful and unsafe.  Skyramp advisors have contributed ideas and comments to improve the website, although none agree with every idea at Skyramp.  All are space enthusiasts and willing to help promote the idea of ground assisted launch, and will help or maybe work for any study or company willing to fund ground assist concepts.  I asked some to add personal endorsements here, and we welcome more from any expert in the space industry.

David Maker - Space Physicist 

     I am no space expert, but I know we need single stage to orbit, and the only possibility is with assisted launch.  Nothing is thrown away, just pay for the fuel. If the vehicle can be made small (relative to the  shuttle let's say) it can be mass produced perhaps  (like jet airliners are now ), launches done frequently, costs then go down and down. You have the possibility of a commercial airline type of operation. Space can be developed much as the west was after cross country train travel was initiated in the late 1800 s. Furthermore, children will have reason to hope; we could all go into space and not just some elite cadre of astronauts, with space travel providing a mere Disney TV show for the rest of us.

    Contrast that state of affairs with all the expense associated with the ET (shuttle) fuel tank manufacture, SRB refurbishment in Utah, etc. where thousands of technicians are needed, each with a high salary.  You then have billion dollar launches; the cost of putting a  pound  into orbit with the shuttle is greater than the price of a pound of gold. There is no large development of space  possible with these kinds of costs.  There is no known way with chemical rockets  that  can fly back (i.e. can reenter and land) to get  single stage to orbit with just static launch. It all comes down to the mass ratio, or the ratio of the mass of the fuel to the mass of the rocket full of fuel. This ratio must be greater than .9 for hydrogen-oxygen burn for example to achieve single stage to orbit which is not the case for any known reusable RLV single stage to orbit concept.

     In that regard it takes a lot of fuel to lift a lot of fuel, so by giving the rocket even a mach 1 or 2 initial velocity (out of the mach 24 needed to orbit)  there results a great gain in fuel savings, and with a mach 2 assisted launch, the possibility of single stage to orbit for a X-33 type vehicle. Care must be taken however that your assisted launch methodology does not require added weight to the RLV which would then negate the benefits of assisted launch. Also assisted launch must  be done close to the equator to take advantage of the 1000mph eastward rotational velocity that is already there. Furthermore  the RLV must be "fat" so that the ratio of fuel to surface area (i.e. deadweight structure) is as large as possible, explaining of course why the X-33 design was "'fat" for example. Furthermore you really need assisted launch for single stage to orbit, you must not "compromise", use  partial reusability as with the space shuttle.  In that regard reusable launch technology has this unfortunate characteristic that if you go only half way with it (the large fuel tank attached to the shuttle is not reusable for example) the reusability technology actually costs far  more  than ordinary multistage expendable rocketry.

      If you observe these precautions about how to do assisted launch, you will find that assisted launch is the only way single stage to orbit will ever happen. We are learning that  lesson every day from all these failed attempts  to use  reinvented  1950s chemical rocket static launch technology to produce anything that is important and that hasn't been done before in space launch, we get this even  from  X-prize contenders; decade after decade entrepreneurs and rocket scientist NASA "kids" just out of college  proposing  these static launch ideas and then (predictably) being shown to be not viable because of the .9 mass ratio limitation.

     So assisted launch isn't humbug. The humbug is all these attempts to reinvent static launch over and over again, ad nauseum .  So why isn't the idea assisted launch taking root?  It is clear there is very little knowledge of these fine points of assisted launch (discussed above) and of the physics associated with that concept.  I found for example that these "experts" can't even solve the deltaV equation for assisted launch, they seem only to be able to plug numbers into Excel spreadsheets. So all the rocket scientist community does is recycle old 50 s and 60s static launch concepts after they are long forgotten, which they get away with  because these ideas appear new to the unknowledgeable.  They need  courage to try these new assisted launch ideas but apparently this courage is lacking. In that regard, how can the upper level bureaucracy at NASA obtain that courage when they lack the technical knowledge to understand these ideas (e.g. O'Keefe is an accountant?)   

     Essentially, we are flailing about decade after decade (mid 70s to 2003 so far)  on space launch  and apparently there is no end in sight. Your kids will probably partake in this flailing process as well.  Sad.  I know this from my work with the propulsion people (evaluating exotic propulsion concepts)  and participated in a NASA study on assisted launch (my name is on the official NASA document). In fact I did some calculations in 1996  that showed that the X-33-Venturstar concept  would not make it to orbit without assisted launch. I sent these calculations up the chain of command all the way to Goldin. I was told that my letter stirred up a hornets nest in NASA propulsion circles, with the result that my post doc money (in that regard my PhD is in physics)  was taken away so that I am no longer with NASA.

      But we now know that the X-33-Venturstar would not make it to orbit  and of course they could not screw up this project since they needed this shuttle replacement.  This inability to orbit by the way is the principle reason the  X-33 was cancelled; you need to talk to the propulsion experts to hear that. I was right of course about the nonviability of the  X-33 . In that  regard  (note also the recent  dire consequences of there being no shuttle replacement) being right at NASA doesn't matter a twit, they just killed the messenger.

    I endorse pneumatic assisted launch, a 2.5 mile long near vertical tube built near the equator pushing up RLV at 6g s to at least mach 2 or higher. Also rocket sled assisted launch has the advantage that no high tech and expensive maglev or catapult track must be built.  

Marty Fritz - Spaceflight Command and Control Engineer

     I worked for 15 years as an Electrical and System Engineer at Boeing designing and testing air and space vehicles computerized flight control and command systems, both manned and unmanned.  One important aspect of this work has been the design and analysis of systems for creating safe and reliable platforms in the incredible harsh, and sometimes destructive environment of space flight.  The nature of spaceflight requires highly powerful and complex machines, but this complexity gives rise to more and more potential parallel failure modes increasing the risk of catastrophic system failure.  As the industry pushes for more reusable launch platforms in the interest of savings cost, the vehicles become even more complex compounding the problem. One of the beauties of the skyramp approach is that the trend to ever more complex launch systems is reversed making it possible to simultaneously improve safety and reliability and reduce cost.  

     A particularly vulnerable point in conventional rocket launch is during the first moments following ignition.  At this point the vehicle is at maximum weight and mechanical stress and is also highly unstable due to the low air speeds.  Controls at this regime of flight must have high mechanical control authority and use complex control algorithms to keep the vehicle under control.  Generally the rocket engines have nozzles with hydraulically controlled gymbols to provide thrust vectoring. (Think of balancing a ruler on the end of your finger.)  Any failure in either the mechanical or computerized aspects of the flight control system at this point are unrecoverable.  To mitigate the risk of system failure these control systems are usually duplicated and operated in parallel to make an overall fault tolerant system.  Usually three or more parallel systems are employed.  The Space Shuttle uses five redundant flight control computers!

     A key advantage of a rail launch system is the mechanically constrained first stage.  No complicated control system is required because the track is doing the mechanical guidance.  Once the vehicle leaves the track, you have plenty of air speed to use control surfaces, such as small fins, to guide the vehicle out of the atmosphere.  No rocket nozzle gymbols!  As it leaves the atmosphere the vehicle converts from control surface to side thruster guidance but the problem is much reduced because the environment, from the control system point of view, is so much simpler and benign - space has no cross winds or other weather phenomenon.  The vehicle is also much lighter due to less fuel, so the control authority necessary is reduced.  With rail launch you only have to build a spacecraft - not an aircraft that must fly into space.  All that adds up to less equipment which means lower weight, less money, and higher reliability.

 

Editor: In 1964, Douglas Aircraft proposed a rail launched spacecraft called Hyperion. (above)

Clint Stallard III - Pneumatic Catapult Engineer

     I have been investigating alternative catapult technology as lead engineer for the Internal Combustion Catapult Aircraft Launch System (ICCALS) technology for Northrop for many years. The Navy liked the idea of combustion gas aircraft launches, but not the additional logistics involved for the explosion-proof fuel. I have investigated alternate uses of catapult technology for horizontal launch assist of space vehicles. Preliminary investigation in conjunction with the Vehicle Analysis Branch at NASA Langley is promising. 

     I was excited to find the Skyramp group had also discovered the value of catapult launches. I advocate a combustion gas pneumatic launched ramjet-powered reusable first stage fly-back aircraft which can reach Mach 5-7. Pound for pound, ramjets are far more powerful and fuel efficient than rockets, and a catapult solves the problem of accelerating the aircraft to near mach for ramjet ignition. NASA has made a major investment in hypersonic research and I've been discussing this concept with NASA engineers. I also proposed use of combustion gas catapult launch tubes installed in a vertical orientation and attached to NASA launch vehicle. This provides the equivalent of an additional stage for the rocket which is ground-based and not attached to the launch vehicle.

     As part of the preliminary investigation to date, Ted Talay (now retired) of the Launch Vehicle Analysis Branch conducted a preliminary analysis of a single C-13 catapult used with a three stage 6,175 lb.  Black Brandt X sounding rocket. The catapult provided a 7.1% payload increase or a 6% altitude increase. Additionally, Mr. Talay analyzed a 3 stage Bantam Launcher weighing 83,000 pounds and capable of placing 220 lbs. into low earth orbit if launched conventionally. Use of the catapult for launch assist of the Bantam rocket raised the payload capacity to 329 lbs. for the same orbit as an ideal case with no change to the rocket. The equivalent solid rocket booster to provide this performance would cost $100,000 per launch and provides a cost basis for trade study purposes.

     An additional study of heavy lift rocket applications was provided by Roger Lepsch of the same group. The vehicle selected for analysis was a Single Stage To Orbit (SSTO) delta wing vehicle weighing 2.4 million pounds and a payload of 45,000 pounds to orbit. A launch end speed of 250 FPS (170 MPH or 150 KTS) was assumed. The preliminary results showed ideally a 40-45% increase in payload to orbit if the launch vehicle can be braced internally to handle the additional acceleration load. Conversely, with no change in payload, the launch vehicle may be as much as a million pounds lighter with catapult launch assist. The current combustion gas catapult goal is Mach 1+ launch speed and 6G capability for a horizontal launch installation

Dr. Werner Von Braun - Rocket Systems Genius

     Dr. Braun was the technical advisor for the 1951 film "When World's Collide" where Braun envisioned a ramp launched spacecraft. (right)  Braun was part of the team that developed the German V-1, which was launched off ramps inclined 30 degrees.  Although Braun helped perfect vertical launch with the V-2, he recognized the simplicity of ramp launches for large craft like the one depicted in his film.  However, the US military preferred more expensive and complex vertical launched vehicles to allow the simultaneous launch of hundreds of ballistic nuclear tipped missiles.

2008 Sky Ramp Technology