ment18 Posted October 4, 2016 Share Posted October 4, 2016 (edited) 21 minutes ago, Technical Ben said: Wait. I've just realised... I'm an idiot. And Elon Musk (and his staff) are (possibly) as well. From testing the launcher/refuel idea... could they not just use the booster minus payload (a fairing or something on top) AS the refuel tanker? I'll be able to try out the two ideas in KSP, but no idea on the practical RL costs and results. You would need some engines for thrust in a vacuum, possibly? 1. maneuvering for docking 2. reentering enormous rocket booster, they'd have to add a heat shield 3. tiny payload Now the tanker craft however could be a decent SSTO. Edited October 4, 2016 by ment18 Link to comment Share on other sites More sharing options...
Technical Ben Posted October 4, 2016 Share Posted October 4, 2016 (edited) Ok, I agree it's rather big for docking. Re-entry is a big problem. Payload should be ok (it would be the tanker, it's taking up the fuel). But separating out the fuel for launch and fuel for transfer would be a serious problem. Where as the tanker would have separate tanks for this. Basically, these ideas work in KSP because the engineering is skipped (we can fuel flow around the "where do we put the fuel" problem) and I can power land through the re-entry and docking if needed. Edited October 4, 2016 by Technical Ben Link to comment Share on other sites More sharing options...
Nefrums Posted October 4, 2016 Share Posted October 4, 2016 Why do you think that payload of a single stage would be even remotely close to what you could get with a two stage rocket? Link to comment Share on other sites More sharing options...
Technical Ben Posted October 4, 2016 Share Posted October 4, 2016 (edited) I was of the opinion this was a "big dumb rocket", not that it would in it's self give the same payload, but that we could just scale it up/put bigger tanks in for SSTO. But as said, that was from a KSP perspective where cost is not an issue. (Or structural integrity, or logistics etc etc) I was negating the cost of the extra fuel needed (and wasted), but to some extent wondering if it was worth it to skip the construction cost of a second ship. I'm literally going to test the idea in KSP once I get the landings down to a T. Besides the biggest problem is the elephant in the room. How is that thing going to land millimetre perfect in that hole as it did in the video? Edited October 4, 2016 by Technical Ben Link to comment Share on other sites More sharing options...
ment18 Posted October 4, 2016 Share Posted October 4, 2016 56 minutes ago, Technical Ben said: I was of the opinion this was a "big dumb rocket", not that it would in it's self give the same payload, but that we could just scale it up/put bigger tanks in for SSTO. But as said, that was from a KSP perspective where cost is not an issue. (Or structural integrity, or logistics etc etc) I was negating the cost of the extra fuel needed (and wasted), but to some extent wondering if it was worth it to skip the construction cost of a second ship. I'm literally going to test the idea in KSP once I get the landings down to a T. Besides the biggest problem is the elephant in the room. How is that thing going to land millimetre perfect in that hole as it did in the video? Firstly, making a new even bigger rocket ( 100+ raptors?) is going to cost a lot of development money. The tanker is very similar to the ship, so it shouldn't cost much. They have more than mm of tolerance. They should have at least a meter of tolerance, and can do lots of cool stuff to increase that. (moving landing pad). They said the fins on the booster should help alignment at the end. The booster can also hover. Falcon can't. Link to comment Share on other sites More sharing options...
Northstar1989 Posted October 5, 2016 Share Posted October 5, 2016 On Tuesday, October 04, 2016 at 11:47 AM, wumpus said: This assumes that the "cargo only" ships are chemical (probably methane&oxygen) and use hohmann transfers with similar delta-v requirements. From your numbers above ["6.4 and 8 km/s",vs. "3-4 km/s on a slower trajectory"], cutting the delta-v in half should cut the fuel needed by an order of magnitude (not so much if the McargoT is coming back without being refueled at Mars). While the cost of the fuel (on Earth) might be trivial, getting it to LEO is over $1000/lb (so far). Going the "slow way" via gravity tricks should work with Mars (although it and Venus have the least benefit of such tricks). Also using ion propulsion would reduce the fuel mass by at least 80%. The only reason that costs should be anywhere near 90% of a crewed MCT is impatience and cost of designing a completely different McargoT. Beyond that, consider the benefits of using such a McargoT to transport fuel to an eccentric orbit (heading toward Mars) around Earth with ~2000m/s delta-v difference between it and LEO. The crew docks with the fuel tanker (likely a fueled up stage, until "we" are that confident in in-space refueling) and then proceeds to burn at Perigee. This bypasses the tyranny of the rocket equation by breaking the burns into two 2km/s burns instead of one 4km/s. And while you can't really break natural laws, you *can* pay for the extra 2km/s in cheap ion propulsion delta-v instead of expensive methane/oxygen delta-v. Less sure about cycler ships: typically the delta-v needed to dock/capture/etc plus the cost to get it started should end up a wash. Presumably any justification would be due to life support benefits and/or the benefits of maneuvering an asteroid to serve as the base of a cycler (even then the delta-v to dock/undock isn't free). These are so far in the future to not worry about (and hopefully propulsion systems will have changed by then). My assumption was that the cargo-only MCT would be chemical, and would use the same aeroshell as the passenger MCT. Also that, if getting payload to Mars would cost $140k/ton with Musk's current MCT, then getting fuel to LEO on his reusable tanker would be so cheap as to be comparatively negligible in costs. Obviously if fuel costs in LEO were high, you went through the trouble of designing a cargo MCT that relied on ion engines, or you engaged in repeated gravity-assists and refueling in an eccentric orbit of the MCT then cost-savings for sending cargo seperately would be much higher than 8-11%. But I assumed that none of these would hold true, except perhaps use of a single lunar gravity-assist. Regards, Northstar On Tuesday, October 04, 2016 at 4:22 PM, ment18 said: Firstly, making a new even bigger rocket ( 100+ raptors?) is going to cost a lot of development money. The tanker is very similar to the ship, so it shouldn't cost much. They have more than mm of tolerance. They should have at least a meter of tolerance, and can do lots of cool stuff to increase that. (moving landing pad). They said the fins on the booster should help alignment at the end. The booster can also hover. Falcon can't. What I think he meant is wouldn't just using the booster as an SSTO and sending the fuel in more launches be cheaper than designing an entirely new tanker? The tanker, however is based on the aeroshell of the crewed upper stage. So it really shouldn't be that expensive to develop. And even if you *could* use the booster as a tanker in itself, having a two-stage design dramatically increases your payload. So this would then be another case of balancing initial R&D investment vs. long-term running costs for the colonization program. Except this time, the cost-savings would be a LOT higher than 8-11% as incentive for developing the tanker... Regards, Northstar Link to comment Share on other sites More sharing options...
magnemoe Posted October 5, 2016 Share Posted October 5, 2016 9 hours ago, Northstar1989 said: What I think he meant is wouldn't just using the booster as an SSTO and sending the fuel in more launches be cheaper than designing an entirely new tanker? The tanker, however is based on the aeroshell of the crewed upper stage. So it really shouldn't be that expensive to develop. And even if you *could* use the booster as a tanker in itself, having a two-stage design dramatically increases your payload. So this would then be another case of balancing initial R&D investment vs. long-term running costs for the colonization program. Except this time, the cost-savings would be a LOT higher than 8-11% as incentive for developing the tanker... Regards, Northstar its the other way around making making an tanker of second stage would be easy, I'm pretty sure they will make an cargo only version you could put fuel tanks in. They might remove the huge hatch and don't need payload adapters and such stuff. Making the first stage an SSTO would require massive rework. unlike the second stage its not designed to re-enter from orbit. just from mach 6 like the falcon 9 first stage. Link to comment Share on other sites More sharing options...
magnemoe Posted October 5, 2016 Share Posted October 5, 2016 22 hours ago, mikegarrison said: They wouldn't normally expect to use the LES unless there was something severely wrong with the rocket, so designing it to protect the rocket wouldn't make a lot of sense. As I understand its not only the fire from the LES who it would be possible to protect from and also smart as burning an hole in the oxygen tank would be energetic but also the force of the blast who is likely to destabilize the rocket. Link to comment Share on other sites More sharing options...
tater Posted October 5, 2016 Share Posted October 5, 2016 BTW lifestream starts at 10:45 ET: https://www.blueorigin.com Link to comment Share on other sites More sharing options...
Mitchz95 Posted October 5, 2016 Share Posted October 5, 2016 Anyone know what time the actual launch is? Link to comment Share on other sites More sharing options...
Kryten Posted October 5, 2016 Share Posted October 5, 2016 Stream for the test is up; Link to comment Share on other sites More sharing options...
wumpus Posted October 5, 2016 Share Posted October 5, 2016 3 hours ago, magnemoe said: Making the first stage an SSTO would require massive rework. unlike the second stage its not designed to re-enter from orbit. just from mach 6 like the falcon 9 first stage. I was under the impression that the [recoverable] first stage was expected to provide a ton more delta-v than the [recoverable] falcon 9. I'm pretty sure I've seen numbers like 6km/s floating around (and I've always been wary of such issues for falcon heavy), but this could have easily been mistaking mach 6 for 6km/s. Breaking your stages into 2km/s and 7km/s seems unlikely to be optimal, especially with the same fuel (the falcon 9 is much closer to even when launched with no recovery attempt). I suspect they may want the first stage to go faster, although having that monster come in hot would certainly be scary. Link to comment Share on other sites More sharing options...
magnemoe Posted October 5, 2016 Share Posted October 5, 2016 8 minutes ago, wumpus said: I was under the impression that the [recoverable] first stage was expected to provide a ton more delta-v than the [recoverable] falcon 9. I'm pretty sure I've seen numbers like 6km/s floating around (and I've always been wary of such issues for falcon heavy), but this could have easily been mistaking mach 6 for 6km/s. Breaking your stages into 2km/s and 7km/s seems unlikely to be optimal, especially with the same fuel (the falcon 9 is much closer to even when launched with no recovery attempt). I suspect they may want the first stage to go faster, although having that monster come in hot would certainly be scary. 6 km/s would be insane for an first stage, the second tend to have most of the dV. Link to comment Share on other sites More sharing options...
Mitchz95 Posted October 5, 2016 Share Posted October 5, 2016 Looks like launch is at exactly 11:00. (Half an hour from now.) Link to comment Share on other sites More sharing options...
Rakaydos Posted October 5, 2016 Share Posted October 5, 2016 Industry standard is a powerful first stage and a small circularizing upperstage. SpaceX has pioneered the "low and slow" stage, with the first stage just getting the second high enough for the vac nozzles to work, then coming home. Link to comment Share on other sites More sharing options...
Aetharan Posted October 5, 2016 Share Posted October 5, 2016 (edited) I don't know whether to root for a successful, unexpected recovery of the booster (and subsequent museum interment) or for the big boom on the desert floor. Edit: 5 minutes into this hold, I'm going crazy with anticipation! Edited October 5, 2016 by Aetharan Link to comment Share on other sites More sharing options...
CatastrophicFailure Posted October 5, 2016 Share Posted October 5, 2016 8 minutes now, kind of a long hold here... something wrong, maybe? Link to comment Share on other sites More sharing options...
Spaceception Posted October 5, 2016 Share Posted October 5, 2016 Still holding at 1 minute 13 seconds. Link to comment Share on other sites More sharing options...
Aetharan Posted October 5, 2016 Share Posted October 5, 2016 Just now, CatastrophicFailure said: 8 minutes now, kind of a long hold here... something wrong, maybe? I really hope not. I'm going to keep watching until they either cut the stream or launch the rocket, though. Link to comment Share on other sites More sharing options...
Mitchz95 Posted October 5, 2016 Share Posted October 5, 2016 And no explanation, either. I know Blue Origin is kinda secretive, but still... Link to comment Share on other sites More sharing options...
Spaceception Posted October 5, 2016 Share Posted October 5, 2016 13 minute hold and counting Link to comment Share on other sites More sharing options...
Mitchz95 Posted October 5, 2016 Share Posted October 5, 2016 (edited) Apparently they had to recycle software on the rocket to stop the countdown. Now they're assessing whether to continue or scrub for the day. Edited October 5, 2016 by Mitchz95 Link to comment Share on other sites More sharing options...
Aetharan Posted October 5, 2016 Share Posted October 5, 2016 It's an unmanned flight for which they fully intend to press backspace at max-q and sac the booster. Light the candle already! Link to comment Share on other sites More sharing options...
Spaceception Posted October 5, 2016 Share Posted October 5, 2016 1 minute ago, Aetharan said: It's an unmanned flight for which they fully intend to press backspace at max-q and sac the booster. Light the candle already! Well when you put it like that... T minus 14 minutes!! @Aetharan I think they saw your comment. Link to comment Share on other sites More sharing options...
Mitchz95 Posted October 5, 2016 Share Posted October 5, 2016 Back on track! The delay is annoying, but better safe than sorry. Link to comment Share on other sites More sharing options...
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