Robert Clark

Sorry about that. Three of the four posts in the nascent blog are directly related to the discussion and all can be seen on the same page of the link I provided. However, the three posts are these: TUESDAY, MAY 1, 2012 Low Cost HLV. http://exoscientist.blogspot.com/2012/05/low-cost-hlv.html MONDAY, MAY 7, 2012 Low Cost HLV, page 2: Comparison to the S-IC Stage. http://exoscientist.blogspot.com/2012/05/low-cost-hlv-page-2.html WEDNESDAY, MAY 2, 2012 SpaceX Dragon spacecraft for low cost trips to the Moon. http://exoscientist.blogspot.com/2012/05/spacex-dragon-spacecraft-for-low-cost.html Bob Clark

Sorry about that. A typo in the web address. I corrected it in the post. Bob Clark

[This is in reference to an argument attached below that the Ariane 5 core stage can be SSTO with 3 Vulcain engines.] The most important accomplishment of SpaceX may turn out to be they showed in such stark terms the savings possible when launchers are privately financed: SpaceX Might Be Able To Teach NASA A Lesson. May 23, 2011 By Frank Morring, Jr. Washington The SpaceX experience of developing a launcher in the Falcon 9 at 1/10th the cost of a government financed one also holds for the crew capsule development costs since the Dragon capsule cost about $300 million to develop while the Orion costs several billion and still counting. So it can't be said this cost saving is just due to the Falcon 9 being, so far, unmanned. Speaking about Orion and billions of dollars, I read an article about plans to use the Orion on the Ariane 5 to get a European manned spaceflight capability: French govt study backs Orion Ariane 5 launch. By Rob Coppinger on January 8, 2010 4:45 PM http://www.flightglo.../01/french.html This would cost several billion dollars to man-rate the Ariane 5. I have to believe the solid rocket boosters, which can not be shut down when started, play a significant role in that high cost. The article mentions also the core stage would have to be strengthened. But such strengthening is based on it having to support a 20 mT Orion capsule and a 20 mT upper stage which wouldn't be used with a much smaller capsule such as the Dragon, at a dry mass of about 4 mT. Note also that quite likely an even smaller manned capsule could be designed at about a 2 mT dry mass to carry a 3 man crew, which given its half size compared to the Dragon, might cost in the range of only $150 million to develop as privately financed. It's hard to imagine that private investment could not be found to finance such a capsule development when it could lead to a manned European space capability. In regards to the costs of a privately financed SSTO version of the Ariane launcher we might make a comparison to the Falcon 9. It cost about $300 million to develop and this includes both the structure and engines, the engines making up the largest share of the development cost of a launcher. But for the SSTO Ariane both engine and structure are already developed and it's only a single stage instead of the two stages of the Falcon 9. You would have the development cost of adding 2 additional engines and of the new avionics, but again I have to be believe the development cost would once again be less than the SpaceX development cost of the Falcon 9 if privately financed. I also read that the ESA is attempting to decide whether to upgrade the Ariane 5 or move to a Next Generation Launcher(NGL): Ariane rocket aims to pick up the pace. 25 June 2011 Last updated at 06:39 ET http://www.bbc.co.uk...onment-13911901 Thu, 9 February, 2012 France, Germany To Establish Working Group To Resolve Ariane 5 Differences. By Peter B. de Selding http://www.spacenews...ifferences.html If the NGL is chosen then a quite expensive new large engine development would have to be made, and the launcher might not enter service until 2025. In contrast the SSTO-Ariane, given that the engine and stage already exist, a prototype probably could be ready within 1 to 2 years, and moreover by using a second stage it could also be used to launch the medium sized payloads. So the SSTO-Ariane would solve the twin problems at low cost of providing Europe with a manned spaceflight capability and giving it a lower cost medium lift capability. Bob Clark Blog: http://exoscientist.blogspot.com ====================================================================== Newsgroups: sci.space.policy, sci.astro, sci.physics, sci.space.history, rec.arts.sf.science From: Robert Clark Date: Thu, 8 Sep 2011 13:56:20 -0700 (PDT) Subject: Re: A kerosene-fueled X-33 as a single stage to orbit vehicle. I saw this discussed on a space oriented forum: WSJ: Europe Ends Independent Pursuit of Manned Space Travel. In this post I discussed getting a SSTO by replacing the Vulcain engine on the Ariane 5 core with a SSME: Newsgroups: sci.space.policy, sci.astro, sci.physics, sci.space.history From: Robert Clark Date: Wed, 23 Feb 2011 10:14:42 -0800 (PST) Subject: Re: Some proposals for low cost heavy lift launchers. http://groups.google...586cc269f?hl=en However, in point of fact Europe can produce a manned launch vehicle from currently *existing*, European components. This will consist of the Ariane 5 and three Vulcain engines. The calculations below use the Ariane 5 generic "G" version. You might need to add another Vulcain for the larger evolution "E" version of the Ariane 5 core. In a following post I'll also show that the Hermes spaceplane also can become a SSTO by filling the entire fuselage aft of the cockpit with hydrocarbon propellant. The impetus for trying the calculation for a Ariane 5 core based SSTO using Vulcains instead of the SSME was from a report by SpaceX that you could get the same performance from a planned heavy lift first stage using a lower performance Merlin 2 compared to the high performance RS-84 engine. The reason was the lower Isp of the Merlin was made up for by its lower weight. THIS IS A VERY IMPORTANT FACT BECAUSE WHAT IT MEANS IS THAT YOU DON'T NEED THE HIGH PERFORMANCE ENGINES TO GET THE SSTO. YOU CAN USE ENGINES OF LOWER CHAMBER PRESSURE AND SIMPLER COMBUSTION CYCLES, SUCH AS THE VULCAIN WITH A CA. 100 BAR COMBUSTION PRESSURE AND A GAS GENERATOR CYCLE. THIS MEANS THE ENGINES ARE CHEAPER, EASIER TO MAKE REUSABLE, REQUIRE LESS ROUTINE MAINTENANCE, AND CAN LAST FOR MANY RESTARTS. In the discussion of the Ariane/Vulcain SSTO below, I note you can get a prototype, test vehicle quite quickly since the components are already existing. To improve the payload though you would want to use altitude compensation on the Vulcains. In a following post I'll discuss some methods of altitude compensation. In regards to achieving this at low cost, I think the most important accomplishment of SpaceX might turn out to be that they showed in stark terms that privately financed spacecraft, both launchers and crew capsules, can be accomplished at 1/10th the developmental cost of government financed ones. Imagine a manned, reusable orbital launcher, for example, instead of costing, say, $3 billion, only costing $300 million to develop. Here's how you can get an all European manned SSTO using the Ariane 5 core stage but with Vulcain engines this time. Note that this is one that can be produced from currently existing components, aside from the capsule, so at least an unmanned prototype vehicle can be manufactured and tested in the short term and at lowered development cost. We'll use three Vulcain 2's instead of the 1 normally used with the Ariane 5 core stage. There are varying specifications given on the Vulcain 2 depending on the source. I'll use the Astronautix site: Vulcain 2. http://www.astronaut...es/vulcain2.htm From the sea level thrust given there, using three Vulcain 2's will give us one engine out capability. The weight is given as 1,800 kg. So adding on two will take the dry mass from 12 mT to 15.6 mT. To calculate the delta-V achieved I'll use the idea again to just use the vacuum Isp, but adding the loss due to back pressure onto the delta-V required for orbit, as I discussed previously. However, here for hydrogen fuel which has higher gravity loss, I'll use a higher required delta-V of 9,400 m/s when you add on the back pressure loss. With the vacuum Isp given for the Vulcain 2 of 434 s, we get a payload of 3.8 mT: 434*9.8ln(1+158/(15.6+3.8)) = 9,412 m/s. Note this is just using the standard nozzle Isp for the Vulcain, no altitude compensation. So this could be tested, like, tomorrow. However, for a SSTO you definitely want to use altitude compensation. Using engine performance programs such as ProPEP we can calculate that using long nozzles, you can get a vacuum Isp of 470 s for this engine. As a point of comparison of how high an Isp you can get even with a low chamber pressure engine as long as you have a long nozzle, or equivalent, note that the RL10-B2 with a ca. 250 to 1 area ratio, and only a ca. 40 bar chamber pressure, gets a 465 s vacuum Isp. So we'll assume we can get a comparable Isp by using altitude compensation. This allows us to get payload of 8 mT: 470*9.8ln(1+158/(15.6+8) = 9,400 m/s. This allows us to add a Dragon-sized capsule and also the reentry and landing systems to make it reusable. Bob Clark ======================================================================

Two separate teams announced plans last month to do asteroidal and lunar mining: Google billionaires, James Cameron backing space resource venture. By Alan Boyle Renowned scientists join tech visionaries at Moon Express to mine the Moon for planetary resources. There has been alot of skepticism evinced about the possible profitability of such plans. However, in regards to the justification for these endeavors, several studies have shown many of the important metals for high technology such as platinum at present global growth rates, especially in the emerging economies such as China, will be depleted within decades: Earth's natural wealth: an audit 23 May 2007 NewScientist.com news service David Cohen http://www.science.o...t/027ns_005.htm If these reports are true, and there is some uncertainty in the estimates, then such asteroid mining missions, might turn out to be not merely amusing topics of conversation, but actual necessities. In that New Scientist article the author seems to be implying the uncertainties in the estimates of impending scarcity come from how the producers are reporting their stocks and available mine-able ore. That is, they may be underreporting them to artificially keep prices high. But with some of these key minerals predicted to run out within two decades clearly this is something that needs to be determined definitively. Maybe we need to send in UN inspectors into their accounting departments and into their actual mines like we send in inspectors for rogue nuclear states. In any case, here are some peer-reviewed papers that discuss this issue: Metal stocks and sustainability. R. B. Gordon*, M. Bertram†,‡, and T. E. Graedel†,§ PNAS January 31, 2006 vol. 103 no. 5 1209-1214. An impending platinum crisis and its implications for the future of the automobile. Chi-Jen Yang Energy Policy. Volume 37, Issue 5, May 2009, Pages 1805-1808. And of course also if such scarcity estimates are valid, then this would clearly have a major impact on the question of the profitability of the space mining ventures. On my blog I present some calculations to show such lunar or asteroidal missions can be accomplished at much lower cost than realized: advertising link removed by moderator Bob Clark

Hello all. New member here. I teach math at an east coast university. My interests are all areas of science but especially math, physics, astronomy, space exploration. Bob Clark