For the past few days, I’ve been jumping-out-of-my-shoes excited from reading the cover story of the February 2010 issue of Wired magazine entitled “The New Industrial Revolution,” by long-tail theorist Chris Anderson, and the related issue of Make magazine, the theme of which is “Desktop Manufacturing.”

The Wired article is simply a must-read for anyone interested in making things — in turning ideas into physical reality.

The basic premise is this: The tools of digital design and fabrication — which traditionally were high-priced, closed-source, corporate-entity terrain — are now becoming cheap enough to find their way into the hands of small startups, hackerspaces, and even individuals.

Digital Fabrication and the MakerBot

What is digital fabrication? 100kGarages says it best:

Digital fabrication allows a precise design to be created using computer software and then passed to another computer attached to a fabrication or CNC tool, which are capable of producing the 3D design with high precision and detail. This fidelity to the design means that the parts or components are cut, drilled, or machined exactly as expected and exactly the same each time.

Both Make and Wired profile MakerBot Industries, and their associated physical and virtual communities, NYC Resistor and Thingiverse. MakerBot is a three-person startup in NYC which sells kits for their “Cupcake CNC” 3D printers — computer-controlled devices that can take a digital file of a 3D object and “print” the real thing right on your desktop — all for under $1000.

NYC Resistor is a Brooklyn hackerspace where the MakerBot founders met and tested ideas for their prototype device, and Thingiverse is their online repository of downloadable and printable objects — all created and uploaded by their community of MakerBot users.

You can learn more about MakerBot and Thingiverse from the video below:

Open-Source Hardware and the Long Tail

What this means is that more and more garage and basement hackers are going to be able to bring their ideas to marketplace. They’ll be able to create the “long tail” of products that the big corporations can’t, while retaining the flexibility to change direction swiftly and iterate more often.

What’s more, the shared nature of what Tom Igoe calls “open fabrication” will allow makers from all over the world to collaborate on open-source hardware projects, just like they do with software today.

Big changes are coming.

Cool Links

Some popular 3D CAD software:

• SolidWorks The (pricey) real deal.
• Rhino 3D Free trial.
• Alibre Design Free (Xpress version).
• Google SketchUp Free.

Some Personal CNC tools:

• Lumenlab “micRo” universal fabricator.
• ShopBot Shop-sized mill/router.
• Tormach Bench-top CNC mills.

This excellent video from the TED Talks website deals with biomimicry, the concept of getting engineering inspiration from the natural world.

From the abstract: With 3.8 billion years of research and development on its side, nature has already solved problems that human designers and engineers still struggle with.

In this inspiring talk, Janine Benyus provides fascinating examples of biomimicry — the way humans mimic nature in the products we build and the systems we implement. And because the champion adapters in the natural world are, by definition, those that can survive without destroying the environment that sustains them, biomimicry can contribute to the long-term health of our planet.

~ from Google Tech Talks, July 31, 2007

ABSTRACT

Software developers usually confine themselves to working entirely within the runtime environment of a computer just pushing around bits and pixels. Even virtual worlds such as Second Life exist only in the confines of our CPUs.

On the other hand, hardware hacking has really taken off in recent years and there are now magazines such as MAKE devoted to modifying everyday objects. It’s a lot easier than software jockeys may expect, and this talk will begin with an entertaining exploration of simple ways to get started with linking a computer to real-world objects.

But what happens when you knock down the boundaries between the real world and a virtual world? The talk goes on to show specific techniques and examples for linking real-world objects into the Second Life environment so that changes in the real world can be reflected in SL and vice versa.

Jonathan Oxer is founder of Internet Vision Technologies, author of “How To Build A Website And Stay Sane” ( www.stay-sane.com) and “Ubuntu Hacks” (www.ubuntuhacks.com), is currently President of Linux Australia, convened the last 5 Debian Miniconferences, and sits on various boards and advisory panels for groups including Swinburne University and the federal e-Research Coordinating Committee.

On August 6, 1997, Korean Air flight 801, a Boeing 747, crashed at Nimitz Hill, Guam, with 237 passengers on board. The airplane had been cleared to land at Guam International Airport and crashed into high terrain about 3 miles southwest of the airport. 228 people were killed, and the airplane was destroyed by impact forces. Post-crash analysis revealed no mechanical defects with the aircraft (NTSB, 1997).

The National Transportation Safety Board calls this type of accident Controlled Flight Into Terrain (CFIT), in which a functioning airplane is essentially flown into the ground due simply to the pilots’ lack of a clear picture of where they are (Arthur, 2003). According to a study from the Flight Safety Foundation, nearly 80 percent of all fatal airline accidents can be attributed to CFIT or approach-and-landing accidents (North, 1999). Clearly something needs to be done to address this situation and reduce these preventable pilot-error accidents.

During times of reduced visibility, pilots rely solely on the instrumentation in the cockpit and reports from Air Traffic Control (ATC) to maintain a mental picture of their position in space relative to terrain, airports, navigational aids and other air traffic. This “picture” is known as Situational Awareness (SA). Historically, airline and corporate cockpits provided situational awareness through a jungle of dials and gauges, each with its own purpose, communicating such information as bearing and distance from navigational aids (NAVAIDS), aircraft attitude, altitude, airspeed, heading, and various system-health data.

However, with the advent of TV-like screens to display data, called Electronic Flight Instrumentation Systems (EFIS), in military and later commercial cockpits, this instrument jungle was considerably reduced. One CRT or LCD screen was adequate to present the aircraft’s airspeed, attitude, altitude and heading to the pilot. This reduced the number of places to which a pilot’s eye had to travel around the instrument panel when “scanning” the gauges during low-visibility flight. The subsequent decrease in pilot workload meant an increase in situational awareness.

But it was not enough. The problem was this: the early EFIS systems simply replicated the presentation of the old electro-mechanical dials and gauges on a TV-like screen. Little attempt was made to utilize this technology to bring a more user-friendly and intuitive presentation to the cockpit (Nordwall, 2003). Pilots still had to read numbers and chase needles, then mentally create the situational-awareness “picture.”

An emerging concept called Synthetic Vision is a revolutionary attempt to rectify this problem, using EFIS technology to bring maximum situational awareness to the cockpit in the hopes of reducing pilot-error accidents, especially CFIT.

The Synthetic Vision System

Simply put, the idea behind the Synthetic Vision System (SVS) is to use currently-available liquid-crystal (LCD) display technology, Global Positioning System (GPS) receivers and an onboard digital database of terrain, obstacles and airports to provide pilots with a computer-generated, three-dimensional view of the outside world during reduced-visibility flight (Stark, 2001). The primary focus of current research is to provide technology that will not only inhabit the instrument panels of futuristic air transports, but will also be available for retrofit into existing aircraft, including airliners, corporate jets, helicopters and even general aviation light planes.

The Synthetic Vision Systems Project was begun under NASA’s Aviation Safety Program whose stated goal is “to develop and demonstrate technologies that contribute to a reduction in the aviation fatal accident rate by a factor of 5 by year 2007.” The program is a partnership that includes NASA, the Federal Aviation Administration (FAA), members the aviation industry and the Department of Defense.

The purpose of the SVS Project is to design and test a variety of intuitive displays that provide pilots with a perspective view of terrain, obstacles and even real-time traffic and weather information that is “congruent with the pilot’s natural mode of spatial information gathering” (Stark, 2001). Essentially, this means that the more accurately a display can simulate flight under daylight, high-visibility conditions, the better a pilot’s situational awareness.

In addition to experimenting with different views of terrain, coloring, shading, texturing and display size, NASA’s SVS Project is also evaluating several types of course guidance symbology. Current EFIS systems use a variation of the classic “flight director” symbology, in which a crosshairs or miniature aircraft is presented on the attitude indicator (or “artificial horizon”) and guides the pilot to the proper pitch and bank attitudes in order to track the desired course.

However, the 3-D view of the terrain provided by the SVS allows for a novel type of course guidance that shows both current position and the future path of the aircraft. Such systems are called “Tunnel Guidance” or “Highway In The Sky” (HITS). These can appear as a series of boxes strung out in space through which a pilot must fly in order to stay on course.

HITS symbology “allows the pilot to assess the future trajectory relative to the environment at a glance, thus increasing the likelihood of detection of conflicts between the programmed path and the terrain,” as well as allowing smoother and less-tiring aircraft control since the pilot can more easily anticipate future control movements (Theunissen, 2000). In addition, HITS symbology allows a more accurate flight path over all phases of flight including departure, enroute and approach, compared to traditional tracking of the Course Deviation Indicator (CDI) needles found in current cockpits (Chelton). [See image, above right.]

And Synthetic Vision Systems aren’t just prototypes that are gestating in government simulators and university research programs. Actual flight-ready hardware is getting some real-world tests in one of the toughest and historically most dangerous flight environments in the world: Alaska.

The Capstone Program

Due to the rugged terrain, limited navaid and ATC coverage, and unpredictable weather, the state of Alaska was chosen to initiate tests of new technology that will improve aviation safety and efficiency, and eventually provide the techniques essential to the modernization of the entire National Airspace System. The Capstone Program is a joint industry and FAA Alaskan Region effort to provide a working environment for day-to-day operations of these new systems.

Begun in 1999, Phase I of the Capstone Program provided commercial operators in the Yukon-Kuskokwim delta region with GPS navigation receivers, multi-function color LCD displays, and transceivers that helped aircraft see each other during flights in reduced visibility, all free of charge with participation in the program. This equipment provided pilots with access to non-radar (i.e. no ATC) environments that had previously been limited to visual flight operations, and increased the number of airports served by instrument approaches. Pilots’ situational awareness was increased dramatically, simply by bringing information into the cockpit which included terrain, weather, traffic and accurate aircraft position.

Phase II of Capstone began in 2002, moving to the more “environmentally challenged” Southeast Alaska, which is plagued with bad weather, low visibility and rugged terrain. Phase II heralded the first commercial flight of an aircraft equipped with an SVS on March 31, 2003, using a twin-engine Piper Seneca and a Chelton FlightLogic� Electronic Flight Information System with Synthetic Vision (EFIS-SV).

The Chelton FlightLogic� system consisted of two separate LCD displays. The Primary Flight Display (PFD) featured real-time SVS 3-D terrain and HITS flight path symbology. The Navigation Display (ND) presented a GPS-driven moving map which had the capability to depict the aircraft’s selected course, terrain, obstacles, air traffic and weather data all on the same screen. Initial tests have shown the SV-HITS system provides precision-approach accuracy to course guidance along the entire route of flight, and significantly reduces the chances for CFIT accidents.

Research on SVS and Human Factors

Substantial research is currently being done to evaluate the effectiveness of Synthetic Vision Systems in improving situational awareness, refining aircraft control in low-visibility flight scenarios and reducing or eliminating instances of Controlled Flight Into Terrain. The following example studies focus on slightly different pilot groups and evaluate different facets of pilot performance while using SVS on both a quantitative and qualitative level.

Both studies utilize a simulated Synthetic Vision System as part of their experimental group, each displaying computer-generated 3-D terrain and several using tunnel-in-the-sky guidance. In both studies, use of the SVS system was found to reduce pilot workload, improve aircraft control, and increase situational awareness substantially compared to baseline display systems.

Research Example # 1: Private Pilots

The first investigation was undertaken by Takallu, et al., at the NASA Langley Research Center in Virginia. The focus was on low-time General Aviation (GA) pilots having limited instrument flight skills. A common GA accident scenario involves non-Instrument-rated pilots inadvertently flying from Visual Meteorological Conditions (or VMC, in which the ground and horizon are clearly visible and are used as the primary aircraft course and attitude references) into Instrument Meteorological Conditions (or IMC, in which the ground and horizon are obscured by clouds, fog or haze, and the flight instruments become the primary means of controlling the aircraft’s course and attitude). In such a scenario, the low-time Private Pilot is taught to execute a 180 degree level turn by reference to the instruments in order to hopefully return to visual conditions. Loss of aircraft control or CFIT commonly results.

In this study, 17 GA pilots with Private Pilot, Airplane Single-Engine Land ratings participated. None of the pilots had any instrument training beyond that required for the Private Pilot certificate. The pilots were tasked to evaluate three (3) different instrument display concepts in a flight simulator at Langley’s General Aviation Work Station.

• Display 1, referred to as the Attitude Indicator (AI) was the baseline display, designed to replicate the standard “six-pack” of round electro-mechanical gauges in the average light plane cockpit.
• Display 2, referred to as the Electronic Attitude Indicator (EAI) featured an enlarged attitude indicator representative of the current EFIS “glass cockpit” displays found in most commercial and corporate aircraft.
• Display 3 was called the SVS display, but was identical to the EAI except that instead of the “brown ground-blue sky” depiction of the standard electronic attitude indicator, the SVS featured computer-generated terrain imagery. No tunnel-in-the-sky symbology was incorporated.

Visual cues were also presented in the flight simulator, giving pilots the ability to look out the “window” for attitude references as much as meteorological conditions would permit. Pilot performance parameters such as heading, airspeed, altitude, bank angle and pitch attitude were evaluated on a quantitative basis. Human factors questionnaires were administered after each session, evaluating the pilots’ perceptions of situational awareness on a qualitative basis.

Each flight session was five minutes in length and involved a straight and level flight beginning in VMC and progressing rapidly into IMC. Pilots were expected to maintain aircraft control using visual cues (i.e. out the “window”) while possible, and then transition to the instrument display when visual reference to the horizon was lost. Once IMC was encountered, the pilots were tasked with executing a 180 degree level turn followed by a constant-airspeed climb and a constant-airspeed descent of 1000 feet each, all by reference to the instrument display. Each of the pilots flew four scenarios three separate times, once with each display type.

The results were as predicted: In every one of the scenarios, pilots demonstrated smoother control inputs, smaller and fewer control input errors, and smaller deviations of airspeed, heading and altitude with the SVS display. Interestingly, however, in several cases, such as altitude control, errors were greater with the EAI display than with the baseline AI display, seeming to suggest that simply depicting standard gauges on an LCD screen does little to improve pilot performance.

In addition, pilots overwhelmingly reported a lower workload and improved situational awareness (SA) during flight in IMC with the SVS display compared to the other two. According to the authors, these findings demonstrated that a display which intuitively presents flight-critical data to the pilot and more realistically simulates visual flying cues will lead directly to a reduced level of flying errors, vastly improved SA, and a reduction of loss-of-control and CFIT accidents.

Research on SVS and Human Factors

Research Example # 2: Professional Pilots

Arthur, et al. conducted the following experiment in the Visual Imaging Simulator for Transport Aircraft Systems (VISTAS III) at the NASA Langley Research Center. The hypothesis for this experiment is that “a Synthetic Vision System will improve the pilot’s ability to detect and avoid a potential CFIT compared to conventional flight instrumentation.” The major focus was to test SVS display size configurations that would easily retrofit into existing corporate and airline fleets.

Since the goal of the study was to evaluate the effect of Synthetic Vision of avoiding CFIT, the flight scenarios featured what the authors termed a “rare event” technique, in which an unexpected, potential CFIT incident was incorporated once for each pilot at the conclusion of a series of IMC approach and departure attempts.

The Displays. Three display sizes were evaluated, a Size “A” display that could be retrofitted into existing Primary Flight Display (PFD) slots on Boeing 757-767 aircraft, a Size “D” that would fit in B-777 PFD slots, and the largest was a Size “X” that represented probable display space alloted on future aircraft. Each of the display concepts included a Terrain Awareness and Warning System (TAWS) and a Vertical Situation Display (VSD), which showed a vertical profile of the terrain along the desired course. Both TAWS and the VSD were incorporated into one secondary Navigation Display (ND).

The PFDs incorporated the SVS technology, or the baseline display as appropriate. Six of the PFD concepts used some variation of a Synthetic Vision System. One PFD concept was used as the baseline, and depicted the conventional Electronic Attitude Direction Indicator (EADI) found in most of today’s airline and corporate cockpits. Course guidance on the baseline EADI display was the traditional “flight director” symbology. Guidance on the SVS displays was provided by “Highway-In-The-Sky” symbology.

The Pilots. Sixteen pilots participated in the test, 15 airline pilots and one NASA researcher. The subjects averaged 8200 hours of logged flight experience. The pilots were briefed on the display concepts and participated in a two-hour training session. The “rare event” scenario was not mentioned, although the pilots were expected to maintain separation from the terrain at all times.

The Flight Scenarios. The pilots were tasked with flying a circling approach in IMC to runway 7 at the “terrain challenged” Eagle County Regional Airport in Colorado. At 200 feet above ground level, the pilots were expected to go around and execute a missed approach procedure the led to a nearby navaid. All of the pilots flew the same procedure several times with different displays. The final run for each of the pilots ended with the “rare event” CFIT scenario. In the rare event scenario, the missed approach course was altered in the flight management computer, so that the PFD’s flight director or HITS symbology would provide guidance into the terrain. The pilots were not informed that this run would be any different than the previous.

The Results. As predicted, the users of the SVS displays demonstrated significantly more accurate lateral and vertical tracking of the desired course compared to the users of the baseline EADI display. Twelve of the 16 test subjects flew the CFIT “rare event” scenario with one of the SVS PFDs. All twelve pilots noticed and avoided the CFIT. “On average, pilots with an SVS display noticed the potential CFIT 53.6 seconds before impact with the terrain.” The remaining four pilots flew the CFIT scenario with the baseline display. All four pilots had a CFIT event. Three pilots impacted the terrain and one passed within 58 feet of a mountain peak, unaware of any terrain conflict. In addition, two unplanned CFIT impacts occurred with the baseline display while executing the circling maneuver from base leg to final approach.

This experiment clearly demonstrated the benefit of the Synthetic Vision System in providing better pilot situational awareness, increased accuracy, lower cockpit workload, and more confidence in knowledge of terrain clearance. The rare event scenario illustrated dramatically the advantage of SVS for identifying and avoiding potential CFIT incidents.

Current and Future SVS Applications

In 2003, Chelton Flight Systems (mentioned earlier in conjunction with the Capstone program) received the first FAA certification of a Synthetic Vision System with Highway-In-The Sky technology. The Chelton EFIS-SVS can now be found on a wide range of general aviation aircraft, from the Beechcraft King Air 200 to the Bell 206 helicopter.

Chelton’s EFIS-SVS was also used on Steve Fossett’s non-stop, non-refuelled flight around the world. His aircraft, the GlobalFlyer, was equipped with two of the displays, one used as a PFD and the other as ND.

Chelton Flight Systems EFIS provided Mr. Fossett with critical information on aircraft performance and navigation. It was his primary source for flight instrumentation, providing a real-time moving map perspective along the entire route of flight, along with seamless three-dimensional terrain modeling. Coupled to a three-axis autopilot, the EFIS played a significant role in reducing pilot workload and in keeping the aircraft flying through a steady flow of green rectangular boxes that created a virtual Highway-In-The-Sky, affirming the aircraft was on course. ~ Chelton Flight Systems

Other avionics manufacturers such as Honeywell and Rockwell Collins are getting on board as well. Both companies are offering larger, integrated avionics displays with easily reconfigurable software that can change to suit the aircraft and the operator. Although these systems don’t specifically offer SVS, the new packages are ready to accept the software as soon as it is certified.

Gulfstream’s PlaneView cockpit also offers large LCD displays, and several Gulfstream aircraft have the option of incorporating Gulfstream’s proprietary Enhanced Vision System (EVS), which received provisional FAA certification in late 2002. Gulfstream’s EVS uses an infared sensor to “see” through clouds and fog and depict that image on a head-up display (HUD) in front of the pilot. (Hughes, 2003.)

Summary

Reduced visibility is one of the leading contributors to aviation accidents worldwide. Current EFIS and classic “steam-gauge” cockpit displays have proven to be inadequate in providing pilots with accurate situational awareness and terrain avoidance information. With the computing and display technology available today, a more intuitive means of presenting flight critical data must be designed and evaluated.

Synthetic Vision is that means. Laboratory research and flight test programs have proven that SVS-equipped aircraft are safer and easier to fly. The current number of pilot-error accidents due to low-visibility flight is unacceptable and any technology that can contribute to a reduced accident rate should be implemented as soon as possible.

Copyright © 2000 Aerospace America.   Reprinted with permission.

Image credit: SpaceX

But turbopump engines, whether high pressure or low, were a mistake from the very beginning. They simply are not worth what they cost in time and money. In all the early development efforts, pump-fed systems were preceded by a pressure-fed version. In every case, the mission was accomplished and the program goals met before the development of the pump system was completed. After the X-I broke the sound barrier with its pressure-fed rocket engine, who ever heard of the D-558-2 — powered by a pump-fed engine?

Technically simple two-stage launchers with pressure-fed engines and ocean recovery offer the economical operations that have escaped our high-technology turbopump rockets for more than four decades.

Economic considerations

How could an entire industry have gone so far astray? The answer is simple. In the commercial world, when technologies mature they eventually reach a point where further refinement is not economically justified. However, rocket development in both the U.S. and the Soviet Union had always been government-sponsored. It never had the benefit of the primary limiting influence — economic shakeout.

Development trends were dictated by engineers who strove for high performance. Most often they neither knew nor cared about the cost impact of their designs. High performance and light weight invariably led to complication and high cost. No development really focused on the economic aspects of high performance. No one wanted to. The engineering of complex systems is fun, and most programs were done on almost inexhaustible budgets. No one bothered to ask, "Is it worth the price?"

Back in 1959 I noted, to my great surprise, that the Agena, only one-fifth the size of the Thor intermediate-range ballistic missile, cost more, not less, than the Thor. Here were two liquid-propellant rockets, each comprising one set of tanks, one pump-fed engine, one autopilot, etc. The Agena was almost a scale model of the Thor. Following the accepted practice of the time, we had gone to great lengths to make both of them as small as possible so the mission could be accomplished.

For most missions, a less efficient rocket can do the job of a more efficient one by making the former a bit bigger. With the Agena/Thor situation, we had data that said that efforts to make a given rocket as small as possible might be grossly misdirected.

Another example of such misdirection was the Titan intercontinental ballistic missile (ICBM). The first stage (in 1959) used two engines of about 150,000 lb of thrust each. The single second-stage engine developed 60,000 lb. Again, I found that the smaller engine cost more. The size factor was only little over two, not five as in the case of Thor/Agena, but it still reflected the difference in launch weight between a simple vehicle and a sophisticated one. The absurdity of excessive emphasis on keeping the rocket small became clear.

A third example is the Atlas ICBM. For years the Atlas program had been kept on the back burner because it required a liftoff weight of almost 500,000 lb to throw a hydrogen bomb 6,000 mi. When the weight of the bomb was halved, the Atlas was suddenly considered practical. For some reason, cutting the liftoff weight from 500,000 lb to 250,000 lb made it acceptable.

Development of the 0.5-million-lb Atlas was well along when the order came to downsize it. The original design used five engines of the same size. Cutting the vehicle size in half required a complete redesign, and an entirely new sustainer engine had to be developed. Downsizing the Atlas was an unfortunate mistake. The smaller version cost more, took longer to develop, and provided a vehicle of half the capability.

Apparently, nobody thought of the idea of putting two warheads on an ICBM — that idea came along much later. Had we developed the full-size version, we could have orbited both the Mercury and Gemini astronauts on the same vehicle. Actually, the Atlas never was any good as an ICBM; it came into its own only as a space launch vehicle.

Simplicity, not size, is the key

Truax Sea Dragon concept

Why wings?

Image Credit: Wikipedia

Today, at last, there seems to be an effort under way to develop low-cost launch systems. But most people and organizations in the space community do not really want to develop cheap rockets. Fancy ones are more fun, and, at least at first blush, make more money, create more jobs for more people, and require large organizations to develop, manufacture, and use them.

However, in commercial space, as in most business ventures, cost is the primary consideration. Although perhaps not so obvious, cost is also of great importance in both the exploration of space and in using space for military purposes. It is long past time to stop designing and building engineering tours de force that produce marvelously intricate machines but make access to space more costly.

Many are also obsessed with the idea of flying into space. Why put wings on a space launch vehicle? Perhaps because there are so many airplane pilots in important positions. Perhaps because the Air Force runs the space end of national defense. Perhaps because NASA wants a bigger role for the first A in its name.

The only justification is the unproven (and I believe unfounded) assumption that if the configuration looks and acts like an airplane, it will have operating costs like an airliner's. This is the argument that NASA used for the Space Shuttle, but there was no background of experience to support that assumption. It has been proven to be a very costly error: The Space Shuttle represents a truly marvelous implementation of an absolutely absurd concept. Its development and use have cost some $20 billion-$40 billion, and it has set back economical access to space about 35 years.

Shuttle's costly lessons

Many flawed design choices were made in arriving at the Shuttle's final configuration:

• Wings and landing gear are the heaviest of all possible methods of recovery.
• Parallel staging is less efficient than tandem. More importantly, it also prevents the upper-stage engine from being optimized for vacuum operation.
• Use of two boosters doubles the probability of catastrophic failure. Multiple main engines increase probability of catastrophic failure by a factor of three, even though they may reduce the probability of noncatastrophic failure.
• Opting for segmented booster cases increases the probability of case failure by unnecessarily complicating case design. Monolithic cases were proposed but rejected because Thiokol, a Utah company with no access to water transportation, had to propose a take-apart design.
• Putting a crew on the first flight requires a very high reliability based on ground tests alone. A more sensible procedure would have been to fly the vehicle unmanned for cargo missions until an adequate degree of reliability could be demonstrated, as was done with the Saturn V (the Soviets, incidentally, did fly their shuttle Buran, for the first and only time, without a crew).
• Use of solid propellants in the boosters minimizes the savings that can be had through recovery and reuse. Pressure-fed liquid-propellant boosters, as initially recommended by NASA-Marshall, would have required little more than a wash-down and refueling before reuse. Solids require disassembly and return to the factory, along with replacement of many parts. The cost of solid propellants runs about $7/lb vs. an average of about 10 cents for liquids.
• Throwing away the largest part of the system, the main fuel tank, adds about $50 million to the cost per flight.
• People and cargo should never be mixed. Payloads to be transported to orbit, even for missions requiring a human presence, are 95% "stuff' and at most only 5% "meat." The provisions and safety requirements for the latter cost an order of magnitude more than for the former. Mixing the two burdens cargo flights with the same elaborate safety measures required for people.

Parallel staging, incidentally, led to the need for extremely high engine chamber pressure-3,000 psi. The consequent requirement to pump hydrogen to 6,000 psi created a nightmare of ongoing problems. Had designers chosen to ignite the liquid-propellant engines at booster burnout there would have been no need for high chamber pressures. In fact, the chamber pressure could have been so low that no pumps would have been needed at all.

Engine performance at altitude is almost exclusively a function of the area ratio of the nozzle, and almost independent of combustion pressure. Low-chamber-pressure engines are larger, but no heavier, than those using higher pressure; nor need they occupy more space. If the pressure is low enough, the nose of the first stage can be inserted into the nozzle of the second, reducing (and possibly even eliminating) the interstage structure. Very high area ratios, even those having exit bells extending beyond the diameter of the first stage, can be obtained by corrugating the thin exit cone into a cylinder and draping it over the first stage. Since low-pressure nozzle skirts can be radiation cooled, they can be made of thin stock, and hence are very light.

The vacuum specific impulse calculated for the realistic case of shifting equilibrium changes by no more than 1.5% for chamber pressures ranging from 75 psi to 3,000 psi. True, at the lower pressures the equilibrium changes from shifting to frozen at a lower nozzle area ratio, but even so, the difference in specific impulse almost certainly will not exceed 5%. For a two-stage-to-orbit configuration, with an upper-stage ideal velocity change of 20,000 ft/sec, a 5% difference in specific impulse would change the payload by about 15%. A launch vehicle using a pressure-fed upper stage would therefore have to be only 15% larger to carry the same payload.

Since the relationship of cost to size is very flat, this small increase in size would produce a virtually undetectable increase in cost. It was for this piddling difference that we developed the enormously expensive Shuttle main engines. The payload increase gained by igniting the pressure-fed engine after burnout of the boosters would have more than offset the 15% loss resulting from the slightly lower specific impulse. Thus the Shuttle could have lifted more payload to orbit with a simple, low-cost, pressure-fed main engine.

There simply is no justification for using pumps on a stage that operates in a vacuum. Moreover, even with a first stage, although the difference in performance is somewhat greater, there is no economic justification for using pumps. If a pressure-fed first stage has to be a bit larger, the slight difference in cost attributable to the larger size will be overwhelmed by the incremental cost of developing, building, and using the more complex system. A completely reusable, pressure-fed two-stage launch vehicle can be built with a gross-weight-to-payload ratio of 35. The same ratio for the Space Shuttle is 68. All that cost and complexity produced a product only half as good! The ratio of parts count is at least a hundred to one; the disparity in cost would be at least as great.

Recovery costs

t/Space CXV

Drawbacks of SSTO

Lockheed Martin X-33. Credit: Wikipedia

Formula for cheap access to space

Getting into space is a simple problem. It need not be very expensive. It can be done with a simple rocket at very low cost. It takes a lot of energy, but that energy costs only about $6/lb of payload. No new technology at all is needed. But we have to use the right technology, most of which has been around for four or five decades. We must stop trying to do it the hard way. The formula for cheap access to space involves only a few rules:

• Make the rocket bigger than it has to be.
• Use two stages to orbit, with a single engine per stage.
• Make it simple, using pressure-fed propulsion for both stages.
• Conduct launch operations from the ocean, well offshore.
• Recover the first stage by parachute in the ocean.
• Probably recover the second stage by parachute in the ocean. (Some believe that launch vehicles can be made so cheap that there is no point in recovering them. While recovery of first stages by parachute is so easy that there is no question about the payoff, the jury is still out on upper stages. We have never tried to recover an upper stage using a heat shield plus a parachute.)
• Fly it without a crew, at least initially.

Sea launches and recoveries impose no limit on size. We must build our launchers big to achieve the really important uses for space, such as orbiting solar power stations, space factories, and manned missions to the planets. The technology to get us into space for $30/lb has been around for 40 years. In our infatuation with "high tech," we have simply refused to recognize it. We should throw out 90% of the "improvements" in liquid rockets made in the last four decades, refine pressure-fed rockets a little, and apply the technology of the '50s to recovering both vehicles as well as payloads.

We appear to have learned nothing from the Shuttle program, and are getting set to repeat the error. I hope this trend will not prevail.