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SpaceX video showing Falcon 9 stages and Dragon performing avertical landing
Greg (Strider) Moore wrote:
I suspect it'll be harder to do than suggested and take a few tries, but hey, it's his money. I agree if he want to waste his money no skin off my nose. But Jeff and Greg I frankly I don't understand why shoot for full re-usability when 90% of the cost recovery is probably in just getting the Merlins back. Why not just drop them back using a ballute that can float them on the sea surface for water recovery and harden them against salt water? Dave |
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SpaceX video showing Falcon 9 stages and Dragon performing avertical landing
On Oct 8, 5:40*pm, David Spain wrote:
Greg (Strider) Moore wrote: I suspect it'll be harder to do than suggested and take a few tries, but hey, it's his money. I agree if he want to waste his money no skin off my nose. But Jeff and Greg I frankly I don't understand why shoot for full re-usability when 90% of the cost recovery is probably in just getting the Merlins back. Why not just drop them back using a ballute that can float them on the sea surface for water recovery and harden them against salt water? Dave One possibility is that SpaceX is fishing for U.S. Air Force R&D money. USAF has been playing with the idea of fly back boosters for whatever comes after EELV. SpaceX probably wants to play that game. - Ed Kyle |
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SpaceX video showing Falcon 9 stages and Dragon performing a vertical landing
In article , nospam@
127.0.0.1 says... Greg (Strider) Moore wrote: I suspect it'll be harder to do than suggested and take a few tries, but hey, it's his money. I agree if he want to waste his money no skin off my nose. But Jeff and Greg I frankly I don't understand why shoot for full re-usability when 90% of the cost recovery is probably in just getting the Merlins back. Because recovering them intact attached to the first stage would allow them to "gas and go", which is always going to be cheaper than re- integrating the engines on essentially a new launch vehicle. That and making the engines separate from the rest of the stage means mucking with the design of the plumbing, electronics, and etc. of the first stage. This could hurt reliability due to the introduction of complexity directly into systems required for launch. Adding landing gear and extra fuel doesn't (or at least shouldn't) do this. Why not just drop them back using a ballute that can float them on the sea surface for water recovery and harden them against salt water? How to you "harden" them against salt water? Typical aerospace metallic alloys don't take well to being dunked in salt water. Also note that one of the biggest advantages of reusing an entire stage is that it helps with reliability. You can test fly a reusable stage without risking an actual payload. But, every flight of an expendable vehicle is the first flight for that copy of the hardware, so any problem which crops up with the hardware could lead to a launch failure and loss of payload. Jeff -- " Ares 1 is a prime example of the fact that NASA just can't get it up anymore... and when they can, it doesn't stay up long. " - tinker |
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SpaceX video showing Falcon 9 stages and Dragon performing a vertical landing
In article 60d6e678-bb96-4e9d-9ee1-ed4a7f5899e0
@g29g2000yqh.googlegroups.com, says... One possibility is that SpaceX is fishing for U.S. Air Force R&D money. USAF has been playing with the idea of fly back boosters for whatever comes after EELV. SpaceX probably wants to play that game. Possibly, but such money comes with many strings attached. The biggest reason SpaceX's costs are so low is that they aren't tied up with the typical strings which come with government contracts. Jeff -- " Ares 1 is a prime example of the fact that NASA just can't get it up anymore... and when they can, it doesn't stay up long. " - tinker |
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SpaceX video showing Falcon 9 stages and Dragon performing avertical landing
Jeff Findley wrote:
Because recovering them intact attached to the first stage would allow them to "gas and go", which is always going to be cheaper than re- integrating the engines on essentially a new launch vehicle. ....[snip covered territory]... Also note that one of the biggest advantages of reusing an entire stage is that it helps with reliability. You can test fly a reusable stage without risking an actual payload. But, every flight of an expendable vehicle is the first flight for that copy of the hardware, so any problem which crops up with the hardware could lead to a launch failure and loss of payload. A "gas and go" option would be ideal, however as addressed in the "Grasshopper" thread it would seem we are talking about a nearly vertical trajectory for the 1st stage. Then what? Coming down on chutes until nearly on the ground and then restart a few of the Merlins for the final 1000 ft or so? Coming down solely on engine power seems like a lot of wasted fuel to be taking along on the 'up' leg. I'd be particularly interested in whatever the cross-range capability of this is. I mean what about winds aloft on the descent? The aerodynamics seem mind boggling to me. You mention the complications of changing the 1st stage to handle ejecting the engines from the tankage and I agree with that, but this plan sounds just as complex if not more so to me. Almost to the point of my saying ... pie -- sky.... Dave |
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SpaceX video showing Falcon 9 stages and Dragon performing a vertical landing
In article , nospam@
127.0.0.1 says... Jeff Findley wrote: Because recovering them intact attached to the first stage would allow them to "gas and go", which is always going to be cheaper than re- integrating the engines on essentially a new launch vehicle. ...[snip covered territory]... Also note that one of the biggest advantages of reusing an entire stage is that it helps with reliability. You can test fly a reusable stage without risking an actual payload. But, every flight of an expendable vehicle is the first flight for that copy of the hardware, so any problem which crops up with the hardware could lead to a launch failure and loss of payload. A "gas and go" option would be ideal, however as addressed in the "Grasshopper" thread it would seem we are talking about a nearly vertical trajectory for the 1st stage. Then what? Coming down on chutes until nearly on the ground and then restart a few of the Merlins for the final 1000 ft or so? I would think it would coast downward (near terminal velocity for the relatively "fluffy" stage) and relight the center engine fairly late in the descent to save on fuel. Coming down solely on engine power seems like a lot of wasted fuel to be taking along on the 'up' leg. After killing the horizontal velocity and being put on a trajectory back to the launch site, I'd think that either the engine will be deeply throttled down during the rest of the descent (or perhaps completely off) until needed for final deceleration and landing. Fairly low terminal velocity is an advantage of landing on a planet with a fairly dense atmosphere. I'd be particularly interested in whatever the cross-range capability of this is. I mean what about winds aloft on the descent? The aerodynamics seem mind boggling to me. With the big heavy engines in the base, I'd think a long stage like this would naturally come down engines (and landing gear) towards the ground. It's essentially a really big lawn dart! :-) As for landing, with a big enough engine, you can do pretty much anything you want. ;-) You mention the complications of changing the 1st stage to handle ejecting the engines from the tankage and I agree with that, but this plan sounds just as complex if not more so to me. Almost to the point of my saying ... pie -- sky.... Which is why you start with Grasshopper. You fly a bit, tweak things a bit, and fly some more. What impresses me most about SpaceX is their willingness to actually build, test, and fly hardware on a regular basis. There are some things you just can't learn in simulations. When was the last time you saw one of the big government contractors build and fly something as big as one of their first stages just to test a few things? Jeff -- " Ares 1 is a prime example of the fact that NASA just can't get it up anymore... and when they can, it doesn't stay up long. " - tinker |
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SpaceX video showing Falcon 9 stages and Dragon performing a vertical landing
Jeff Findley wrote:
When was the last time you saw one of the big government contractors build and fly something as big as one of their first stages just to test a few things? Ares 1X?-) rick jones -- I don't interest myself in "why". I think more often in terms of "when", sometimes "where"; always "how much." - Joubert these opinions are mine, all mine; HP might not want them anyway... feel free to post, OR email to rick.jones2 in hp.com but NOT BOTH... |
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SpaceX video showing Falcon 9 stages and Dragon performing a vertical landing
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SpaceX video showing Falcon 9 stages and Dragon performing avertical landing
Jeff Findley wrote:
I would think it would coast downward (near terminal velocity for the relatively "fluffy" stage) and relight the center engine fairly late in the descent to save on fuel. OK on that. But I'm thinking ullage issues, esp. with the RP1, since we're pulling very low G on descent. How is the RP1 pressurized? With nitrogen? With the big heavy engines in the base, I'd think a long stage like this would naturally come down engines (and landing gear) towards the ground. It's essentially a really big lawn dart! :-) My sister caught one of those in her heel once and I think the Consumer Protection Agency finally banned them. Probably should keep that analogy off-line... ;-) As for landing, with a big enough engine, you can do pretty much anything you want. ;-) :-D Which is why you start with Grasshopper. You fly a bit, tweak things a bit, and fly some more. What impresses me most about SpaceX is their willingness to actually build, test, and fly hardware on a regular basis. There are some things you just can't learn in simulations. OK sure, I grant you that. Kudos to SpaceX. But where the heck are they going to test this? Surely not at Patrick. WSMR? BTW, you sure as hell want to be confident that this works *before* sending it aloft from your launch facility. That is, presuming you want to *keep* your launch facility... Try swapping the red labeled Estes engine with the green labeled one on your two-stage model rocket if you want to simulate the effect... ;-) When was the last time you saw one of the big government contractors build and fly something as big as one of their first stages just to test a few things? Not since the days of cost plus (plus plus plus plus....) ;-) Jeff Dave |
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SpaceX video showing Falcon 9 stages and Dragon performing a vertical landing
In article , nospam@
127.0.0.1 says... Jeff Findley wrote: I would think it would coast downward (near terminal velocity for the relatively "fluffy" stage) and relight the center engine fairly late in the descent to save on fuel. OK on that. But I'm thinking ullage issues, esp. with the RP1, since we're pulling very low G on descent. How is the RP1 pressurized? With nitrogen? Low G is all you need to keep the LOX and kerosene settled in the tanks. Besides, before the final landing burn, it's going to be falling at terminal velocity (or close to it), so it will be under 1G at that point in the flight. With the big heavy engines in the base, I'd think a long stage like this would naturally come down engines (and landing gear) towards the ground. It's essentially a really big lawn dart! :-) My sister caught one of those in her heel once and I think the Consumer Protection Agency finally banned them. Probably should keep that analogy off-line... ;-) As for landing, with a big enough engine, you can do pretty much anything you want. ;-) :-D Which is why you start with Grasshopper. You fly a bit, tweak things a bit, and fly some more. What impresses me most about SpaceX is their willingness to actually build, test, and fly hardware on a regular basis. There are some things you just can't learn in simulations. OK sure, I grant you that. Kudos to SpaceX. But where the heck are they going to test this? Surely not at Patrick. WSMR? BTW, you sure as hell want to be confident that this works *before* sending it aloft from your launch facility. That is, presuming you want to *keep* your launch facility... Try swapping the red labeled Estes engine with the green labeled one on your two-stage model rocket if you want to simulate the effect... ;-) Lots of the start-ups have been flying smallish, reusable, liquid fueled VTVL vehicles off of nothing more than a concrete pad, so there shouldn't be much in the way of "launch facility" which would be in danger. Grasshopper is just scaled up a bit from what we're used to seeing. ;-) Besides, accidents should be expected and should be planned for. The biggest failure of DC-XA wasn't the fact that it toppled over and burned upon landing. The biggest failure was that there wasn't a second copy of the hardware available to continue to fly after the first (and only) copy of the hardware was destroyed. Considering Grasshopper looks like it's based on a Falcon 9 first stage, if they "crash and burn", they can always build another copy of the hardware since Falcon 9 is in production. When was the last time you saw one of the big government contractors build and fly something as big as one of their first stages just to test a few things? Not since the days of cost plus (plus plus plus plus....) ;-) There was a lot of progress made in a short amount of time during the 50's and 60's. But that was Cold War era funding and we simply can't afford that anymore. Jeff -- " Ares 1 is a prime example of the fact that NASA just can't get it up anymore... and when they can, it doesn't stay up long. " - tinker |
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