KerbonautInTraining Posted January 21, 2016 Share Posted January 21, 2016 2 minutes ago, Cuky said: Please correct me if this is the wrong thread to post this... SpaceX did a hover test with Dragon V2 Dragon is gonna be reused... so why not? Also paste just the link and then hit enter. It should embed automatically. Link to comment Share on other sites More sharing options...
Streetwind Posted January 21, 2016 Share Posted January 21, 2016 (edited) That particular test was from November 24th, apparently; they've been at this for a while. Or well, maybe they took a short break during the frenzied leadup to RTF, followed by christmas holidays, but you can be pretty sure that they've been busy throughout January too. The nice thing about these kinds of tethered tests is that if necessary, you can literally do them a hundred times in a row with very little effort, collecting a great number of data points. Heck, the Dragon can probably do at least half a dozen of those without even being taken down and refueled Current estimates I've seen speak of over 430 m/s dV, which would yield 45 seconds hovering time. Edited January 21, 2016 by Streetwind Link to comment Share on other sites More sharing options...
Frozen_Heart Posted January 22, 2016 Share Posted January 22, 2016 10 hours ago, KerbonautInTraining said: Slightly off topic: I just realized you can build a full scale Falcon 9 in stock KSP using a cluster of vectors. Also no, there's no chance in hell any of the engines are getting re-used. The kraken is obviously not satisfied with this batch. Tried that. You can only fit 7 of the 9 engines. Link to comment Share on other sites More sharing options...
Darnok Posted January 22, 2016 Share Posted January 22, 2016 I was watching SpaceX videos and they have plans to make reusable both 1st and 2nd stages... so wouldn't be easier for them to start from 2nd stage? It is much lighter and shorter, so it should be easier to land at whatever they want to or am I missing something (except costs difference of both stages)? Link to comment Share on other sites More sharing options...
andrewas Posted January 22, 2016 Share Posted January 22, 2016 The second stage needs to reenter the atmosphere which will require heat shielding, which will have a major impact on the payload and may require a larger first stage to make it worthwhile. Link to comment Share on other sites More sharing options...
fredinno Posted January 22, 2016 Share Posted January 22, 2016 37 minutes ago, Darnok said: I was watching SpaceX videos and they have plans to make reusable both 1st and 2nd stages... so wouldn't be easier for them to start from 2nd stage? It is much lighter and shorter, so it should be easier to land at whatever they want to or am I missing something (except costs difference of both stages)? Also, reusing the 2nd stage is a lot less worth it- you need 1 T of propellant/ 1T of fuel left over, compared to the 1st age, where the ratio is 6:1. I'm quoting from Elon himself here. Link to comment Share on other sites More sharing options...
Darnok Posted January 22, 2016 Share Posted January 22, 2016 19 minutes ago, andrewas said: The second stage needs to reenter the atmosphere which will require heat shielding, which will have a major impact on the payload and may require a larger first stage to make it worthwhile. Yea and that is why IMO they are building rocket from wrong end... they should start with payload and 2nd stage and then go for 1st stage. With current approach they will have to rebuild 1st stage many times and each time add and recalculate everything. 9 minutes ago, fredinno said: Also, reusing the 2nd stage is a lot less worth it- you need 1 T of propellant/ 1T of fuel left over, compared to the 1st age, where the ratio is 6:1. I'm quoting from Elon himself here. True, but with 2nd stage they would probably landed on barge at first time and with working 2nd stage they could rebuild 1st stage once and add all it needs to be resuable. Link to comment Share on other sites More sharing options...
fredinno Posted January 22, 2016 Share Posted January 22, 2016 22 minutes ago, Darnok said: Yea and that is why IMO they are building rocket from wrong end... they should start with payload and 2nd stage and then go for 1st stage. With current approach they will have to rebuild 1st stage many times and each time add and recalculate everything. True, but with 2nd stage they would probably landed on barge at first time and with working 2nd stage they could rebuild 1st stage once and add all it needs to be resuable. You are being too optimistic about the 2nd stage. It would likely have to be rebuilt just as much as the 1st stage, if not more- not to mention Falcon 9 would have to be a larger 4-6 diameter rocket. Link to comment Share on other sites More sharing options...
Frozen_Heart Posted January 22, 2016 Share Posted January 22, 2016 Elon himself said that they no longer plan to reuse the second stage. Its not worth the development time and payload reduction. Link to comment Share on other sites More sharing options...
andrewas Posted January 22, 2016 Share Posted January 22, 2016 30 minutes ago, Darnok said: Yea and that is why IMO they are building rocket from wrong end... they should start with payload and 2nd stage and then go for 1st stage. With current approach they will have to rebuild 1st stage many times and each time add and recalculate everything. True, but with 2nd stage they would probably landed on barge at first time and with working 2nd stage they could rebuild 1st stage once and add all it needs to be resuable. The immediate costs of developing a recoverable second stage are much higher than the recoverable first stage. The impact on payload is much higher, they might need Falcon 9 Heavy to launch payloads that are well within Falcon 9's capability. They need to develop a thermal protection system along with everything needed to recover the first stage. Also, you're overestimating how much easier it would be to recover the second stage - its smaller and lighter, but it only has one engine which means it needs to throttle more deeply to land. Or, they need to incorporate a separate engine just for landing - yet more cost and weight. By doing the first stage first, they get maximum benefit for the least effort. When first stages are routinely recovered and re-used, the costs of using a falcon 9 heavy over a falcon 9 will be much lower, and development of the recoverable second stage can take advantage of the lessons learned recovering first stages. We won't see a second stage run out of hydraulic fluid or suffer from sticky valves. The stages will land using the infrastructure developed for first stages, perhaps at the opposite coast so as not to interfere with first stage recovery. Or maybe the savings from reusing first stages will be low enough that they decide recovering second stages is not viable, and they don't waste money on building a second stage that'll cost a fortune and never pay for itself. Link to comment Share on other sites More sharing options...
KSK Posted January 22, 2016 Share Posted January 22, 2016 (edited) 45 minutes ago, Darnok said: Yea and that is why IMO they are building rocket from wrong end... they should start with payload and 2nd stage and then go for 1st stage. With current approach they will have to rebuild 1st stage many times and each time add and recalculate everything. They did - sort of. The F9 first stage was designed to be modular from the outset - The Falcon Heavy first stage is just three F9 first stages joined together and I imagine it would be quite capable of lifting a reusable second stage and a good sized payload.The question is whether it would have been worth the cost of building a larger first stage for the sake of saving some money by recovering the second stage, bearing in mind that developing a recoverable second stage was also likely to be quite expensive? Apparently the answer was: no it wouldn't. Edited January 22, 2016 by KSK Link to comment Share on other sites More sharing options...
Lukaszenko Posted January 22, 2016 Share Posted January 22, 2016 AND on top of everything, what do you get back with the 2nd stage? 1 engine, as opposed to the first stage's 9 engines. Link to comment Share on other sites More sharing options...
fredinno Posted January 22, 2016 Share Posted January 22, 2016 1 hour ago, Lukaszenko said: AND on top of everything, what do you get back with the 2nd stage? 1 engine, as opposed to the first stage's 9 engines. And engines are the most expensive single part (along with piping and pumps) Link to comment Share on other sites More sharing options...
Cuky Posted January 22, 2016 Share Posted January 22, 2016 @KerbonautInTraining @Albert VDS Thanks for tips, though I managed it myself after 9 or 10 edits of the post. Now reading your posts I finally have a clue as to what I did right on the last try Link to comment Share on other sites More sharing options...
KerbonautInTraining Posted January 22, 2016 Share Posted January 22, 2016 2 hours ago, andrewas said: Also, you're overestimating how much easier it would be to recover the second stage - its smaller and lighter, but it only has one engine which means it needs to throttle more deeply to land. Or, they need to incorporate a separate engine just for landing - yet more cost and weight. The Merlin vacuum's nozzle is WAY over expanded for sea level operation. If you re-lighted it there the flame would separate from the walls of the bell and (if I'm not mistaken) the engine might tear itself apart. Also, seeing as crossfeed is apparently out of the question for FH, does anyone know if they're going to do like the Delta IV Heavy and throttle down the core? Link to comment Share on other sites More sharing options...
Red Iron Crown Posted January 22, 2016 Share Posted January 22, 2016 5 minutes ago, KerbonautInTraining said: Also, seeing as crossfeed is apparently out of the question for FH... When did that happen? Link to comment Share on other sites More sharing options...
KerbonautInTraining Posted January 22, 2016 Share Posted January 22, 2016 2 minutes ago, Red Iron Crown said: When did that happen? I've heard quite a few people mention it on the forums, apparently the turbopumps weren't happy about the arrangement. Link to comment Share on other sites More sharing options...
AngelLestat Posted January 22, 2016 Share Posted January 22, 2016 it is not surprise that they would not use crossfeed for the first missions.. but they will use it eventually. Not sure what is the source of those who said that crossfeed is out of the question... Link to comment Share on other sites More sharing options...
StrandedonEarth Posted January 22, 2016 Share Posted January 22, 2016 1 hour ago, Red Iron Crown said: When did that happen? Something about the complexity and difficulty of shutting down the crossfeed while not starving the turbopumps and not getting flames in bad places. I'm sure it can be done (sump tanks?) but at what cost in weight, complexity, and failure modes? Link to comment Share on other sites More sharing options...
fredinno Posted January 22, 2016 Share Posted January 22, 2016 1 hour ago, StrandedonEarth said: Something about the complexity and difficulty of shutting down the crossfeed while not starving the turbopumps and not getting flames in bad places. I'm sure it can be done (sump tanks?) but at what cost in weight, complexity, and failure modes? Falcon Heavy Reusable is already OP, even w/o cross feed. Only Energia-M had similar payload capacity. Link to comment Share on other sites More sharing options...
softweir Posted January 22, 2016 Share Posted January 22, 2016 If a company has the launch capability, then there is a good chance its existence will create the demand. Projects have to be designed to fit the available launch capability - raise the bar, and customers will be able to consider more ambitious projects. Link to comment Share on other sites More sharing options...
KSK Posted January 22, 2016 Share Posted January 22, 2016 (edited) 24 minutes ago, softweir said: If a company has the launch capability, then there is a good chance its existence will create the demand. Projects have to be designed to fit the available launch capability - raise the bar, and customers will be able to consider more ambitious projects. That's the big hope, yes and it's what SpaceX are banking on I think. And as an unabashed space nerd, I hope it happens too. But there's a finite amount of government money available for science and/or prestige projects and I'm honestly not sure what the next steps for private space are. Tourism might get us a bit farther but that still leaves a lot of missing links to figure out before we get to the cool sci-fi stuff such as Mars programs and Moon bases. Edit. Stupid spellcheckers. Yes I did mean 'sci' and not 'sic'. Preserve me from computers that try to be too helpful. Edited January 22, 2016 by KSK Link to comment Share on other sites More sharing options...
fredinno Posted January 23, 2016 Share Posted January 23, 2016 4 hours ago, softweir said: If a company has the launch capability, then there is a good chance its existence will create the demand. Projects have to be designed to fit the available launch capability - raise the bar, and customers will be able to consider more ambitious projects. That's like SLS-HLV logic, and it's struggling to find anything that might need it due to a lack of defined mission. So disagree. Link to comment Share on other sites More sharing options...
Rakaydos Posted January 23, 2016 Share Posted January 23, 2016 51 minutes ago, fredinno said: That's like SLS-HLV logic, and it's struggling to find anything that might need it due to a lack of defined mission. So disagree. SLS's problem is that it's cheaper to make something smaller and use a different, cheaper rocket. With Falcon Heavy, you can save money by making something BIGGER, less efficent. Dont need micromilimeter machined parts of spaceage materials- just build something that does what you want and ride a bigger (but still relatively affordable) rocket. Link to comment Share on other sites More sharing options...
B787_300 Posted January 23, 2016 Share Posted January 23, 2016 In space flight existence does not create demand. I mean the Russians had Energia and they launched that monster rocket twice. FH has the benefit of it is useful because it can take some of the DIVH business and do more massive things. (although the FH fairing is undersized) Link to comment Share on other sites More sharing options...
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