SpaceX makes history - Page 1
Forum section: electronics / general

author: chris_leyson
author_rank: Super Contributor
timestamp: March 30, 2017, 11:29:57 pm
content: Well done SpaceX, puttung SES-10 into orbit was a flawless missonI think there are another 8 lauches scheduled for this year on pre flown hardware, I wish them luck.

author: rrinker
author_rank: Super Contributor
timestamp: March 31, 2017, 12:32:03 am
content: That is awesome! I totally forgot to watch it. This really will be a game changer.

author: brucehoult
author_rank: Super Contributor
timestamp: March 31, 2017, 10:30:40 am
content: A fantastic achievement, but I got a little bit annoyed at all the people in the media and on twitter saying that this was "the first time an orbital rocket has been relaunched".There's the small matter of Columbia, Challenger, Discovery, Atlantis, and Endeavour which made 4808, 995, 5830, 484, and 4677 orbits of the Earth on 28, 10, 39, 33, and 25 flights, respectively. A Falcon 9 first stage has yet to make a single orbit of Earth (and probably never will, though it's a theoretical possibility with sufficiently light or absent 2nd stage).The Shuttle, sadly, required a lot of very expensive refurbishment work between flights, keeping the estimated marginal cost of an extra flight at or above US$500m throughout it's lifetime. Falcon 9 is around ten times cheaper than that, even as a disposable.In the mid 80s before the Challenger disaster, Challenger and Discovery were each routinely being flown about once every ten weeks. The first two flights of Atlantis (just before Challenger's explosion) were only 54 days apart, less than eight weeks. The gaps between flights were increased after the loss of Challenger, and increased again after the loss of Columbia becoming more like one flight per orbiter every 8 or 10 months.SpaceX have taken 11.5 months between the two flights of this first stage.Of course they have been very very careful to check it carefully. We don't know how much they repaired or replaced, but definitely they inspected or tested absolutely everything.They have said they'd like to try launching the same rocket twice in one day soon. That will have to be one that lands back at the cape. Unless they decide to have them ferry themselves back to the cape from the barge :-)

author: chris_leyson
author_rank: Super Contributor
timestamp: March 31, 2017, 11:11:10 am
content: QuoteAgreed, the shuttle was the first spacecraft to reuse flight hardware but the Falcon 9 is the first booster to autonomously fly itself back and land on a barge and they've repeated this 8 or 9 times now, I think a lot of the media missed the whole point about it being autonomous. Can't wait for the Falcon 9 Heavy flight scheduled for Q3/Q4 later this year.

author: Neilm
author_rank: Super Contributor
timestamp: March 31, 2017, 06:56:54 pm
content: Quote from: chris_leyson on March 31, 2017, 11:11:10 amCloser to the SRBs on the shuttle which parachuted back to earth and were refurbished. However they required a full strip down and replacement of pretty much everything in it. I believe that SpaceX did a strip down of this rocket to check it but reassembled it with minimal replacements

author: CatalinaWOW
author_rank: Super Contributor
timestamp: March 31, 2017, 10:29:52 pm
content: Even if no inspection or repair are required, launching a rocket twice in one day will be an exciting and impressive achievement. Just filling one of these beasts with fuel is a lengthy process, and as SpaceX demonstrated not too long ago, not without risk. I also believe that it will require moving the rocket at least a bit to get from the landing point to a launch stand. They still use umbilicals and a flame pit handle pre-launch control and damage from the long exposure to rocket blast during takeoff.

author: JoeN
author_rank: Frequent Contributor
timestamp: April 01, 2017, 12:43:26 am
content: Quote from: brucehoult on March 31, 2017, 10:30:40 amLaunch it off the barge. Reusable rocket, expendable barge.

author: brucehoult
author_rank: Super Contributor
timestamp: April 01, 2017, 08:08:25 am
content: Quote from: JoeN on April 01, 2017, 12:43:26 amDid you see the failed barge landings and explosions? Those things are tough!

author: David Hess
author_rank: Super Contributor
timestamp: April 01, 2017, 11:57:28 am
content: Quote from: brucehoult on March 31, 2017, 10:30:40 amGo read the Feynman's report about the Shuttle's reliability. The RS-25 engines were suffering cracked turbine blades during operation which would have normally been considered a failure but instead of fixing the problem, NASA redefined the failures as a maintenance problem and rebuilt the engines after every launch so the only part being reused was the orbiter.

author: David Hess
author_rank: Super Contributor
timestamp: April 01, 2017, 12:10:25 pm
content: Quote from: Neilm on March 31, 2017, 06:56:54 pmThe SRBs required a lot of rework. One of the problems with the Shuttle design was the torque transmitted through the hold down bolts in the SRB skirts which would bend the SRB sections out of round. Later NASA increased the hold time time because the Shuttle was moving sideways at launch hitting parts of the launch structure breaking things and this increased the peak torque even further and beyond the design specifications.When the SRBs were rebuilt, the sections were suppose to be checked for roundness and a hydraulic press with a pressure gauge used to push them back into shape. If the required pressure was too high, then they were suppose to be discarded. One of the Challenger findings was that a lot more SRB sections were failing after the hold down time was increased, naturally since the peak torque was much higher, but the solution they implemented was to add another jack into the press for pushing them back into shape and ignoring the design specification of maximum force.

author: brucehoult
author_rank: Super Contributor
timestamp: April 01, 2017, 12:29:16 pm
content: Quote from: David Hess on April 01, 2017, 11:57:28 amDude. I've owned (and re-read multiple times) a copy of "What Do You Care What Other People Think?" since shortly after it came out in 1988, as I enjoyed his earlier "Surely You're Joking, Mr. Feynman!" so much.I'm well aware of the problems with the shuttle and how much of a dog it was, right from the start. In fact it probably started from the deliberate decision of congress in the mid 70s to save on development and capital costs at the expense of maintenance costs by using solid boosters instead of liquid ones, and a number of other bad decisions.What SpaceX is doing now is wonderful work that will benefit the human race immensely.That does not, however, make them the first to reuse a rocket and thus far, their reuse turn-around time is five times longer than NASA was doing routinely in the early 80s.I have every confidence SpaceX will quickly take all the turn-around time records away from the Space Shuttle, and at vastly lower cost, but they have not done it YET. And however shoddy the Shuttle was (and it was), that doesn't rase the fact that it was first.

author: David Hess
author_rank: Super Contributor
timestamp: April 01, 2017, 03:20:54 pm
content: Quote from: brucehoult on April 01, 2017, 12:29:16 pmIf reuse encompasses NASA jacking up the radiator cap and putting a new shuttle under it, then reuse has a low bar.I wonder how much refurbishment SpaceX had to perform. Did they just wash it off, test it, and relaunch it?

author: CatalinaWOW
author_rank: Super Contributor
timestamp: April 01, 2017, 04:51:44 pm
content: Quote from: David Hess on April 01, 2017, 03:20:54 pmDoing five hundred million dollars of rework to relaunch a vehicle that had a unit cost of between 4.5 and 5 billion dollars is a lot different than jacking up the radiator cap and driving a new vehicle under. The Space Shuttle had many flaws, but it was still an impressive technical and political achievement. Unfortunately the requirements for political success often conflicted with those for technical success, adding to the problems.It is unlikely that we will ever know SpaceX refurb costs in detail, as that is competition sensitive information. I wouldn't be surprised if SpaceX has 10% refurb costs, particularly to start. I also suspect that they would be tickled pink if those costs stay in the 10% range, at least for the next several years. Most of their competitors effectively have 100% rework costs.

author: SeanB
author_rank: Super Contributor
timestamp: April 01, 2017, 05:10:51 pm
content: NASA reuse was use the same airframe, replace all the tiles that fell off ( and see what that got them in the end), basically replace the engines because they were badly damaged ( OK some of the bolts and sensors were probably recycled into new engines, but replacing large parts is not reuse even if you resmelt it and turn it back into parts in a foundry), replace fuel cells and RCS system parts, plus of course build a massive new ET structure and a lot of SRB "consumable" parts like shrouds, parachutes and such.For Elon Musk to get the engines, tanks and such back essentially intact and reuse them is a good step forward. Now to get that second stage back as well with low impact on payload will go a long way to cutting cost, but the big parts being reused is still a massive step forward from tossing them away and keeping the payload only.

author: Kleinstein
author_rank: Super Contributor
timestamp: April 01, 2017, 06:16:27 pm
content: I don't think reusing a rocket is not such a sound idea - more like a stupid one. So the date might be well chosen.To reuse the rocket considerable mass is added and the inspections are needed or even more demanding than checking a new rocket. The material and machining itself is not that expensive - it the development and strict testing that make a rocket expensive. At least only reusing the first stage is way better than the shuttle was: The heavy parts needed for reentry made a doomed to be financial failure from the star off.The best achievement of the shuttle program was that they sold it so well to the politicians not only to get money for an idea as stupid as solar roadways, but they even got the Russians to believe it. I still can't believe how they made that.It way better to recycle beer bottles than rockets.

author: brucehoult
author_rank: Super Contributor
timestamp: April 01, 2017, 07:13:10 pm
content: Quote from: Kleinstein on April 01, 2017, 06:16:27 pmAnd so what if mass is added, if you still have the performance to launch the customers' payloads (which Falcon 9 does) and if as a result it makes it robust enough to fly it 100 times?You can bet they'll inspect the hell out of the every flight of the first one, and after the first flight or two of every subsequent one ... but once a few of them have gotten to 100 launches without major problems, the inspection before a 10th or 20th or 30th flight is going to be pretty minimal. You already know it was manufactured properly, and it's not old enough to be suffering fatigue problems yet.Something that is only designed to be reused 2 or 3 times might well end up more expensive, yes, but not when it's seriously reusable like a Boeing or Airbus.

author: JoeN
author_rank: Frequent Contributor
timestamp: April 01, 2017, 07:56:55 pm
content: Quote from: David Hess on April 01, 2017, 12:10:25 pmIn the end, that was justified, was it not? An SBR section never failed from reuse, even after abuse of these design specifications. No SBR ever failed other than the Challanger O-ring problem which would have never killed that SBR anyway (to the SBR it was a minor leak, and the end of its mission), it just ended up killing the external fuel tank because of where it happened.

author: David Hess
author_rank: Super Contributor
timestamp: April 01, 2017, 10:08:11 pm
content: Quote from: JoeN on April 01, 2017, 07:56:55 pmCongress certainly liked the Shuttle but I think their justification had more to do with where the funding went. There may have been a strategic justification in keeping Thiokol and Pratt and Whitney building big ammonium perchlorate boosters.The informal SRB changes were not justified with engineering. It was not documented until someone (Feynman?) noticed another jack installed into the straightening stand and asked what that was for. "Well, we could not straighten the SRB sections according to the specified procedure so we added the jack to force them." Did excessive work hardening of the steel casings have something to do with Challenger disaster? What about extending the hold-down timing increasing the torque on the SRB cases beyond the maximum design torque forcing them further out of round?Feynman included it in his report as an example which called into question the reliability of the Shuttle. Redefining the failure of the RS-25 engines as a maintenance problem was another example. They were suppose to last multiple flights before being rebuilt but could not even last one. I expect that moving the goal posts is easier than engineering. On the other hand, Feynman had great praise for how the shuttle's software was developed and maintained.Quote from: brucehoult on April 01, 2017, 07:13:10 pmAt some point SpaceX discussed this. Most of the weight is in the fuel and most of the cost is in the rocket and because the design has a figure of merit based on the maximum weight and orbit, most launches leave enough fuel for the 1st stage to land which they have demonstrated and that is the most expensive part since it has most of the engines.

author: TerraHertz
author_rank: Super Contributor
timestamp: April 02, 2017, 01:17:50 am
content: I just wish SpaceX could fix the satellite video uplink from the landing barge, so it doesn't lose signal in the few seconds when the rocket is actually closing in and landing. How can that be so hard? It maintains the link despite the barge rocking on waves, so how come the link dies as the rocket approaches? Air vibration from the rocket downdraft? Can't they put a dome over the antenna? Mount the antenna and dome on vibration isolation? What exactly is the problem?Or maybe it's the rocket downwash itself that interrupts the satellite uplink? Then how about using a relay buoy or ship a few Km away?

author: David Hess
author_rank: Super Contributor
timestamp: April 02, 2017, 01:14:46 pm
content: Quote from: TerraHertz on April 02, 2017, 01:17:50 amI have noticed the same thing.The plasma from the engine is RF opaque but it seems unlikely that it always ends up between the transmitter and receiver.Maybe the body of the rocket is acting as a reflector and the changing geometry as it lands is causing multipath? A directional antenna on the barge would fix this.

author: SeanB
author_rank: Super Contributor
timestamp: April 02, 2017, 01:46:46 pm
content: Bet they have a on barge recorder though, and this will be up sometime on the YT channel soon after docking. As they have a support ship close by ( but not too close, just in case the stage lands wrong) I suppose they could just use it as a relay, but I guess where the barge is, out in the mid Atlantic, there is very little high bandwidth coverage from any providers for a basically one off event every few months, so they do not have LOS to a high bandwidth antenna that is directed at them, and have to make do with what is available in any visible beam. Thus poor SNR, low margin before you have a broken digital link and you probably have a big dish on a gyro stabilised mount pointing at the horizon to get a very off axis and way out of footprint signal from a satellite probably over Africa or over the Western USA with a footprint that extends out that far in the fringe.

author: donotdespisethesnake
author_rank: Super Contributor
timestamp: April 03, 2017, 04:19:10 pm
content: Quote from: TerraHertz on April 02, 2017, 01:17:50 amThat's quite funny, SpaceX revolutionize access to space and people complain "hey, where is my real-time feed ?!"Back in the "old days" we had to read the news on bits of paper that arrived the next day. Sometimes there were even pictures!

author: brucehoult
author_rank: Super Contributor
timestamp: April 03, 2017, 09:25:34 pm
content: Quote from: donotdespisethesnake on April 03, 2017, 04:19:10 pm

author: Kleinstein
author_rank: Super Contributor
timestamp: April 04, 2017, 01:44:35 pm
content: Quote from: David Hess on April 01, 2017, 10:08:11 pmThe costs are in the rocket, but how much is a landed rocket really worth: it has to go through testing, much like a new rocket. It also takes extra costs and weight to make the parts to stand a second start. With the costs also much of it is development and testing. Reusing an old rocket only saves you materials and machining.Added weight is significant as it adds to the size of the rocket or reduces the pay load. Things are at least much better with only the first stage, but still any extra weight already has a significant price tag. The added weight for a more durable construction and landing mechanism reduces the weight of the of the second stage that can be brought to the same speed. So you have to compare the extra weight to the second stage, not to the whole rocket. So recovering parts of the rocket only makes sense, if done really early, like with booster rockets for the very early part of the flight.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: April 04, 2017, 02:00:31 pm
content: Quote from: Kleinstein on April 04, 2017, 01:44:35 pmEverything you say is qualitatively true. But the devil is in the details. Musk thinks he has found a sweet spot. He thinks his rockets can be reused 100 times. If he is right, and if the refurb and inspection costs are low he will have a real winner. NASA was making similar predictions before the first shuttle launch. Reality was different. Hopefully Musk has done a better job.

author: brucehoult
author_rank: Super Contributor
timestamp: April 04, 2017, 02:37:25 pm
content: Quote from: Kleinstein on April 04, 2017, 01:44:35 pmReducing the payload by even 50% -- or doubling the size of the rocket -- DO NOT MATTER if it means you can use it 100 times instead of once, with little more than filling the tanks and kicking the tyres on most flights, as is done with commercial airliners.Of course if you do that and then only use it twice ... or have to significantly re-manufacture it each time -- then that's different. That's bad design. There's no fundamental physics that says you can only have bad design, not good design.There's no indication that SpaceX's design for reuse is reducing payload by anywhere near 50%.

author: ajb
author_rank: Super Contributor
timestamp: April 05, 2017, 11:52:58 am
content: They are also now working on recovering the payload fairing, and claim to have had "partial success" with that on this launch. Apparently the fairing itself costs $6M to build and is something of a production bottleneck (being a large composite structure that presumably requires an enormous autoclave and large fixtures that would be expensive to duplicate, meaning they can only have a limited number of fairings in progress at once). I read somewhere that the current plan is to have them position themselves after separation to be aerodynamically stable through reentry and then use steerable parachutes to land on big inflatable pads in the ocean. This would be a revision of the original concept which was to snag them out of the air a laKeyhole film canisters. Musk is also talking about second stage reuse, which presents a number of additional challenges due to the much different dynamics and the fact that the second stage's engine, being optimized for use in vacuum, isn't suitable for use in powered reentry/landing on its own. But if they can pull that off, there's the potential for a 100% reusable rocket, which would be a pretty impressive feat.

author: brucehoult
author_rank: Super Contributor
timestamp: April 05, 2017, 09:23:33 pm
content: Quote from: ajb on April 05, 2017, 11:52:58 amEngines have been done with a two-part nozzle, with the large high-expansion vacuum nozzle sliding up past the engine. Mostly, this is done to make the engine and upper stage shorter until after separation, but it would work equally well in reverse, converting a vacuum-optimized engine into one able to operate at sea level, at reduced efficiency.http://images.slideplayer.com/5/1527507/slides/slide_23.jpg(the problem with the big nozzle for vacuum use is that it expands the exhaust so much that the pressure inside is (much) less than 15 PSI, and if you operate it near sea level then the atmospheric pressure tries to crush it -- and you don't want make it heavy and strong enough to be able to resist that)