-
#1080
by
john smith 19
on 15 Jan, 2018 08:24
-
I think it was broadly 'we thought about it - but at the moment we don't need it; and in any case it was a lot more complicated than we first thought'?
The performance gains from engine development has, it seems, mostly eliminated the need to develop a more capable version of FH (which crossfeed would be) for now - and the future is covered by BFR (or whatever next-generation single stick SpaceX rocket may get built).
Shotwell, (can't recall if it was in an interview or Q&A after a presentation) said something like "We'd do it if a customer asked for it, but so far no customer has requested the level of performance that needs it."
Probably a bit of both.
Keep in mind Merlin performance has risen so much that they are talking
all booster recovery on FH
without cross feed.
And cross feed fittings look like a
massive PITA. Start with the design. You need them 2 part so they break cleanly and seal off both sides while traveling at about M4-6. Keep in mind the designs on the older Atlas versions (prior to engine separation) only had to stop flow from one side, not both (if you want the boosters to retain propellant for recovery).
Do you put them together and run plumbing to one of them? Do you put at the base of each tank?
It turns out this is quite a serious commitment. Once a booster is built for cross feed it's going to
stay built for cross feed, regardless of wheather it's
ever used again as part of an FH.
Given the known FH manifest and the performance required, and the performance now available from non cross fed Merlins that may seem too much trouble for too little benefit.
Despite that it's still a bit surprising that with all those Merlin improvements FH couldn't top 70 (or even 77) tonnes right now.
-
#1081
by
vanoord
on 15 Jan, 2018 09:30
-
Basically, there's no point in building your rocket for about 5% of potential launch customers and in doing so, increase the cost, complexity and thus the possibility of something going awry for the other 95% of your customers.
-
#1082
by
Req
on 15 Jan, 2018 09:45
-
Don't forget that cross-feed may also imply expending the core stage, or at least putting it through a very toasty re-entry.
-
#1083
by
mhenderson
on 15 Jan, 2018 11:01
-
Basically, there's no point in building your rocket for about 5% of potential launch customers and in doing so, increase the cost, complexity and thus the possibility of something going awry for the other 95% of your customers.
However, when it comes to automobiles, many cars are purchased based on their 5% use case (sporty handling, towing a trailer, off-road trails, driving in snow...) and not for daily commuting and errands.
-
#1084
by
Herb Schaltegger
on 15 Jan, 2018 11:37
-
This cross feed discussion is great and all, but there are a number of other general FH threads to rehash it. Nothing about it relates to the Demo mission or the yet-to-be-attempted static fire.
-
#1085
by
Greg Hullender
on 15 Jan, 2018 14:50
-
Sorry to derail the discussion. I was expecting someone to point me to a link. But I really appreciate everyone jumping in to explain it. Thanks!
--Greg (And it's good to see you too, Robin!)
-
#1086
by
laszlo
on 15 Jan, 2018 15:19
-
Is there a party thread for the static fire somewhere? I haven't found one and I don't want to post off-topic/inappropriate for thread content. Thanks.
-
#1087
by
gongora
on 15 Jan, 2018 15:20
-
-
#1088
by
CyndyC
on 15 Jan, 2018 16:22
-
In Red Cross Disaster Services, actively encouraging prevention & preparation plans is a top priority. As idealistic as SpaceX is, I was a little worried about what would become of SpaceX if the FH Demo blows up their brand new pad, but in
gongora's SpaceX manifest, last updated on the 13th, it is a relief(?) to see they have every east coast launch specified to be from SLC-40 for almost the entire 1st quarter, up until Mar20th which isn't specified, and 39A is not specified again after the FH Demo until mid-2018. I guess that's good news?
-
#1089
by
gongora
on 15 Jan, 2018 17:19
-
In Red Cross Disaster Services, actively encouraging prevention & preparation plans is a top priority. As idealistic as SpaceX is, I was a little worried about what would become of SpaceX if the FH Demo blows up their brand new pad, but in gongora's SpaceX manifest, last updated on the 13th, it is a relief(?) to see they have every east coast launch specified to be from SLC-40 for almost the entire 1st quarter, up until Mar20th which isn't specified, and 39A is not specified again after the FH Demo until mid-2018. I guess that's good news?
There is still one possible launch from 39A in the first quarter, we don't know about TESS yet. SpaceX could easily launch all of their East Coast F9 flights from SLC-40 this year (it looks like they would top out around 13-15, not counting Commercial Crew demos). Even though it wouldn't affect the rest of the schedule much, blowing up 39A would still suck.
edit: forgot to count Zuma, so I doubt SpaceX does more than 16 F9 orbital launches from the East Coast this year. Unless maybe Arabsat 6A switches to F9. Then it's 17 tops. Unless there are more government payloads we don't know about yet.
-
#1090
by
Inoeth
on 15 Jan, 2018 18:40
-
In Red Cross Disaster Services, actively encouraging prevention & preparation plans is a top priority. As idealistic as SpaceX is, I was a little worried about what would become of SpaceX if the FH Demo blows up their brand new pad, but in gongora's SpaceX manifest, last updated on the 13th, it is a relief(?) to see they have every east coast launch specified to be from SLC-40 for almost the entire 1st quarter, up until Mar20th which isn't specified, and 39A is not specified again after the FH Demo until mid-2018. I guess that's good news?
There is still one possible launch from 39A in the first quarter, we don't know about TESS yet. SpaceX could easily launch all of their East Coast F9 flights from SLC-40 this year (it looks like they would top out around 13-15, not counting Commercial Crew demos). Even though it wouldn't affect the rest of the schedule much, blowing up 39A would still suck.
edit: forgot to count Zuma, so I doubt SpaceX does more than 16 F9 orbital launches from the East Coast this year. Unless maybe Arabsat 6A switches to F9. Then it's 17 tops. Unless there are more government payloads we don't know about yet.
According to the /r/spacex manifest
https://www.reddit.com/r/SpaceX/wiki/launches/manifest I count 14 launches (including Zuma) from LC 40, a possible total 9 from LC 4E and 7 from 39a (mostly Demo flights and a few actual commercial flights) That adds up to the 30 or so on the books, tho i'm sure some of those will slip into 2019 and a few will be added to that manifest that aren't there now... of course, a couple of those launches are dependent on the FH demo going well- and in general that has to not fail, or if it does so, not in a way that affects the rest of the single stick fleet in order to get close on this manifest...
In any case, back on the FH side of this conversation, are we still looking at a possible end of January launch? If the static fire actually happens successfully on Tuesday or Wednesday I'd guess it could happen, or if they need a second SF, they do that at the end of this week or early next week... To me it looks like SpaceX could pull the end of Jan. launch if the SF is good on Tuesday and they need no extra tests, but otherwise we're looking at early February, and that could easily happen even if things go well...
-
#1091
by
vanoord
on 15 Jan, 2018 19:05
-
If the intention is to get GovSat off from LC40 around the end of the month, then there’s a window of perhaps 7-10 days to static fire FH (possibly twice) and launch it before GovSat.
I don’t see that happening.
-
#1092
by
crandles57
on 15 Jan, 2018 19:49
-
If the intention is to get GovSat off from LC40 around the end of the month, then there’s a window of perhaps 7-10 days to static fire FH (possibly twice) and launch it before GovSat.
I don’t see that happening.
25th launch date was suggested on Jan 9th and only if everything goes perfectly. At that time static fire was planned for Jan 11 so launch sounds like it will be about 2 weeks after static fire and only that soon if everything goes well. With static fire now 16th at earliest add 14 and you get 30th. So I agree, launch before GovSat is looking highly unlikely.
-
#1093
by
TheWire
on 16 Jan, 2018 01:50
-
I think this idea that they loaded all the propellants onto the falcon heavy on Thursday can't be true. Watching on the spaceflight now live stream I only saw 1 big vent from the strongback not the actual rocket, quite sometime before the static fire was called off. It didn't look anything like the falcon 9 during LOX loading. I think they cancelled LOX load before it started or very earlier on.
-
#1094
by
Robotbeat
on 16 Jan, 2018 03:43
-
In Red Cross Disaster Services, actively encouraging prevention & preparation plans is a top priority. As idealistic as SpaceX is, I was a little worried about what would become of SpaceX if the FH Demo blows up their brand new pad, but in gongora's SpaceX manifest, last updated on the 13th, it is a relief(?) to see they have every east coast launch specified to be from SLC-40 for almost the entire 1st quarter, up until Mar20th which isn't specified, and 39A is not specified again after the FH Demo until mid-2018. I guess that's good news?
Well, they'll be busy installing the crew arm sometime soonish assuming FH demo gets safely off the pad.
-
#1095
by
Katana
on 16 Jan, 2018 05:19
-
Basically, there's no point in building your rocket for about 5% of potential launch customers and in doing so, increase the cost, complexity and thus the possibility of something going awry for the other 95% of your customers.
However, when it comes to automobiles, many cars are purchased based on their 5% use case (sporty handling, towing a trailer, off-road trails, driving in snow...) and not for daily commuting and errands.
Launch services compare better to taking buses instead of buying cars.
-
#1096
by
john smith 19
on 16 Jan, 2018 06:35
-
Launch services compare better to taking buses instead of buying cars.
I presume you mean in the sense of a "ticket to ride" rather than an outright purchase of a transport vehicle?
Safety wise I think car crashes massively outnumber bus crashes in the US.
-
#1097
by
puttelino
on 16 Jan, 2018 13:38
-
Look like titanium grid fins on the boosters, Al on the core.
Yes, larger titanium fins are required for increased control authority on the boosters during atmospheric descent. This is due to the more aerodynamic shape of the booster's top, which becomes the "tail" during descent.
Core keeps its blunt top, thus smaller Al fins suffice for controlling atmospheric descent.
I know this is what they said, but it sounds so odd... The other alternative would have been spoilers that are aerodynamic on the way up, but separate the flow when flying backwards...
Not that I don't like the Titanium fins...
My take on it is:
Titanium fins are required for the side boosters to work. For the reentry heating, they would need the centre core to also have titanium grids for the high velocity. But I guess the rocket has enough spare performance to perform a breaking burn instead of a boostback to reduce velocity to normal reentry conditions. The alternative is, they accept the fact that the centre core gets cooked fins and they dont care because they dont plan to reuse this particular core anyway. So great if the reentry works, no big loss if it doesnt.
I do think the core with the highest load is something they want back. It's also a flight regime they have not brought back a booster from before. So i'd say the center core is the most important to get back.
-
#1098
by
M.E.T.
on 16 Jan, 2018 16:47
-
Is the static fire still happening today? Things seem ominously quiet on the Update front. Or have I missed something everyone else is aware of?
By my casual timezone conversion attempt it should be what, about 4 hours or so until the window opens?
-
#1099
by
TheFallen
on 16 Jan, 2018 16:51
-
Is the static fire still happening today? Things seem ominously quiet on the Update front. Or have I missed something everyone else is aware of?
By my casual timezone conversion attempt it should be what, about 4 hours or so until the window opens?
The static fire is still on for 4pm EST today. The silence is a good thing... No news is good news, as SpaceX itself rarely makes a big deal about its static fires until after they've taken place.
Given the known FH manifest and the performance required, and the performance now available from non cross fed Merlins that may seem too much trouble for too little benefit.