Interesting.

Post #377,843 by Another Scott 7/10/13 12:03:10 PM Reply	Interesting. A great technology demonstrator. I'm sure they have their reasons for doing this (which I'm too lazy to look up) but it doesn't make sense to me as a general-purpose lift vehicle from Earth. Mass = fuel and Mass = cost. Carrying around more mass than you need is more expensive than throwing it away and starting over. Now if you're landing on something with a small gravity well and have use for the tanks and so-forth after you leave, well that's a different story. Similarly if you've got propulsion technologies based on Beryllium Spheres and the Omega 13 that gives you more power than you could ever need. But we're not there yet. Very impressive though. Cheers, Scott.
Post #377,857 by altmann 7/10/13 3:49:23 PM Reply	Re: Interesting. Was thinking the same thing. I wonder how much the mass needed for landing fuel compares to the extra mass of lugging around aerodynamic surfaces on the Shuttle compares.
Post #377,859 by drook 7/10/13 4:26:36 PM Reply	Still think they should do ballistic drop crew capsules Simplest technology, fewest moving parts, lightest weight. The only reason for something like the shuttle is if you plan to bring back large objects. The only things big enough to need the shuttle, and valuable enough to warrant the expense, are not in LEO, and thus not available to the shuttle. I'm struggling to see the benefit of this project. It's a great technology demonstrator, but what's the use case? -- Drew
Post #377,869 by malraux 7/10/13 8:15:31 PM Reply	Reuses more of the vehicle As long as the extra fuel is cheaper than the sum of the parts that are recovered, it's economically viable. Regards, -scott Welcome to Rivendell, Mr. Anderson.
Post #377,870 by drook 7/10/13 8:21:57 PM Reply	That's a big "if" It's not just the fuel for the landing, it's the extra fuel to get the landing fuel up there to begin with. And the extra weight of the tank for that extra fuel. And the extra fuel for the weight of the larger tank. etc. etc. etc. Weight is a problem that compounds quickly. Sure, there can be a point where the lines cross, and this demo sets some parameters for drawing those lines. -- Drew
Post #377,872 by malraux 7/10/13 8:56:36 PM Reply	Presumably they've done the calculations And arrived at a number they can live with. Regards, -scott Welcome to Rivendell, Mr. Anderson.
Post #377,876 by drook 7/10/13 10:01:27 PM Reply	Depends on the question you ask though, doesn't it? Which leads to my opinion on the shuttle. They wanted a reusable craft, then came up with the justification afterwards. -- Drew
Post #377,879 by folkert 7/10/13 10:29:55 PM Reply	But honestly... That is how the whole space thing started isn't it? -- greg@gregfolkert.net PGP key 1024D/B524687C 2003-08-05 Fingerprint: E1D3 E3D7 5850 957E FED0 2B3A ED66 6971 B524 687C
Post #377,880 by malraux 7/10/13 10:33:20 PM Reply	Different thing... Shuttle: designed by committee to be excellent at nothing. SpaceX is a business. Regards, -scott Welcome to Rivendell, Mr. Anderson.
Post #377,881 by Another Scott 7/10/13 11:07:13 PM Reply	Good Wikipedia pages on reusable rockets. http://en.wikipedia....le_launch_vehicle It mentions the DC-X - a 1990s research vehicle kinda-sorta similar to the Grasshopper - http://en.wikipedia....nell_Douglas_DC-X The first flight of the DC-XA test vehicle was made on 18 May 1996 and resulted in a minor fire when the deliberate "slow landing" resulted in overheating of the aeroshell. The damage was quickly repaired and the vehicle flew two more times on 7 and 8 June, a 26-hour turnaround. On the second of these flights the vehicle set its altitude and duration records, 3,140 meters and 142 seconds of flight time. Its next flight, on 7 July, proved to be its last. During testing, one of the LOX tanks had been cracked. When a landing strut failed to extend due to a disconnected hydraulic line, the DC-XA fell over and the tank leaked. Normally the structural damage from such a fall would constitute only a setback, but the LOX from the leaking tank fed a fire which severely burned the DC-XA, causing such extensive damage that repairs were impractical.[5] A page on the SpaceX Reusable Launch System (of which the Grasshopper is a partial prototype) is here - http://en.wikipedia...._launching_system Elon's done good, but he's got a long way to go to even get to the 1996 record (325m << 3140m)... Cheers, Scott.

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