<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Hi all,With the recent failure after what appeared to be a picture perfect launch, do you think Elon will press ahead with launch no 4 soon, or will he wait till all facts are known?Three failures out of three attempts does not look good, but it does not appear to be a recurring problem, rather a different problem each time.Would he do better to scrap Falcon & perhaps purchase & modify other launch vehicles with a good track record, i.e Delta 2 (only two failures in 40 years), or perhaps adapt Falcon to embrace known, tried & tested procedures.Or perhaps he's under pressure to deliver quickly from paying customers, hense mistakes are sneaking through? He clearly knows that he has a design that could work, the Merlin's performance was superb, no denying that fact.I know, that I am critical of the private sector as profits come before substance in more ways than one, but is Elon a victim of this? Elon is certainly trying his very best, but is the commercial nature of the business, forcing him to cut corners?IMO launch no 4 will also end up in the Pacific, because things are being rushed, by external market forces, not because of anything he is doing personally?Andrew Brown. <br />Posted by 3488</DIV></p><p>In my opinion he is falling into the same trap as others who thought they could dramatically reduce launch costs through a "commercial" approach to development of a rocket. He and others fail to realize a few things:</p><p>1. Launch vehicle development has largely been conducted by private companies, under contract to the government, who have a profit motive and do not add costs unnecessarily. But a large part of the profit is obtained only by producing a launch vehicle THAT WORKS. The contracts contain tremendous mission success incentives. This is appropriate, particularly when the payloads for those vehicles can be worh BILLIONS.</p><p>2. It is actually a bit difficult to overcome gravity and put a payload into orbit. The value of a pound of useful payload in orbit is very high, so the commercial incentive is to reliably put as much payload up as is possible. It is sufficiently difficult to overcome gravity and the commercial reward for a pound of useful payload in orbit is sufficiently high that launch vehicles must not carry any more inert weight than is absolutely necessary. This means that rocket designs do not incorporate very much redundancy and therefore that the systems on the rocket must be extremely reliable. Rockets are a huge system of single-point failure modes. It takes a lot of expertise and experience to make sure that none of those failure modes actually result in a failute.</p><p>3. Commercial design practices generally are such as to permit a far larger failure rate than is remotely acceptable in a rocket. Standard engineering will not produce a reliable rocket and using good commercial design practices for aerospace systems is a prescription for disaster.</p><p>4. Space-X failures are a result of applying commercial design practices and commercial quality control in a situation where it is simply inappropriate to do so. You can't build a space launcher the same way you build a car, even a high-performance race car. Rocket designers are very conservative in making changes in design philosophy or in selecting technologies without either a proven track record or a lot of testing and understanding of all the operating principles, materials, manufacturing techniques and quality assurance methods.</p><p>5. There are very good reasons for avoiding explosive bolts, pull testing every lot of bolts used, conducting N-ray tests of ordnance lines, testing metal components with x-ray, mag particle, or dye penetrant, .......</p><p>6. All components are usually subjected to a detailed analysis and a full report written. All analyses are reviewed several times and often duplicated by different teams using somewhat different and independent methods. Several rigorous design reviews are held during development and all aspects of the design are put through the ringer by a team of independent experts.</p><p>7. The manufacturing steps in each component are inspected and documented all the way through the process, and each critical step is individually signed off in a log book. Any discrepancy between the as-designed and as-manufactured part is reviewed, analyzed and useage determined by engineering with personal sign-off by the responsible engineer, and that disposition documented. All the data for all components are reviewed by a team of experts, and often more than one team, before it is used on a flight.</p><p>The history of trying to shortcut the rigor of this process is failures on the test stand or in flight and commercial failure. The single most important trait of a launch system is reliability. It is far far more important than launch cost. An unreliable vehicle incurs not only cost of failure but a ruinous cost to the payload owner for launch insurance. </p><p>NASA, under Dan Goldin tried "faster, better, cheaper" by cutting corners, and met with disaster. That is what brought you Mars Pathfinder. </p> <div class="Discussion_UserSignature"> </div>