As for the Heavy I guess there will have to be a specific centre core design. The engineering demands it really, as there will be thrust asymmetries to be accounted for to keep the whole gadget intact. Actually the thrust finesse of the merlins in such a large conjoined cluster now becomes a crucial control issue. The rotational moments are much higher for the off-axis engines. Plus failure modes. Who wants to write that code ? :-))
It isn't the code that is the issue really. It is how much control it can exert. One engine failures aren't much of an issue, you just gimbal the remaining thrust a proverbial hair and it works out. Not any different than what is required for high altitude winds to stay on course. Multi engine failures begin to get more interesting. That might get to be more than the engine gimbals have available. Then you get into a situation where you have to reduce thrust to a working engine. How much, if at all, you can do that before you get to an abort into the water will depend on the flight and heft.
The code doesn't care about the limits while flying. It just drives the controls until they hit their stops. If that isn't enough to control the candle, then other software initiates an abort as the craft veers out of the flight path over the safety limits.
I wonder though if he is doing flight path control on the up phase with engine throttle. It might be reasonable to expect that you want 100% from every engine that runs all the time to try and get the customer into orbit, even if not all the way up. Of course you throttle to keep max q under load limits, but the rest of the time you want all the oomph you can get until MECO time.
Of course engine failures impact how long you have to burn the remaining engines. The existing flight control software has to calculate all of this now. The extension isn't so much writing something that doesn't exist as much as plugging in new engineering constants. Don't forget that the flight software has to be able to be pad updated for the exact amount of fuel load right up until engine start.
Not what I was referring to. The flight path isn't the interesting primary constraint. The key problem, or you don't get anything to any orbit at all, is preventing the craft destroying itself by loss of linkages b/w the cores ( eg. Space Shuttle ). I'd say the big risk is due to sudden asymmetric shears forces b/w barrels when engine is lost ( worst case is outer of side Falcon 9 ).
Cheers, Mike.
I have made this letter longer than usual because I lack the time to make it shorter ...
... and my other CPU is a Ryzen 5950X :-) Blaise Pascal
That, well that isn't code, that is metal, heavy stuff you don't want to lift but are forced to. The trade off is simple, if you lose X engines you aren't going to make it up, your metal doesn't have to be strong enough to hold then. Frankly the worst case is likely all engines running anyway as each side shoves hardest then. Yes a loss makes one side push more than the other but the total push available is less. The sudden stop might set up some vibrations but that's going to happen anyway at MECO when you intentionally shut them off.
BTW on the shuttle the exhaust gas melted the brace. That's an issue for a solid with a hole in the side, not an issue for a liquid.
Speaking of MECO does anyone know if he is going to keep the center running while he sheds the sides or if he is going to do a relight? Also are the sides going to be shed while still running? Or since I think I heard something about fuel cross feed is MECO for the sides going to also be MECO for the center and staging and then he will pop the stack apart and land them separately? Fuel cross feed seems a bit daft as then you have to be sure the cross feed valves close or each simply dumps the fuel you need to land and it is also a bunch of added weight.
Falcon Heavy first flight was described by Elon as currently planned to involved the two side cores being previously used boosters which will land back at the Cape, while the central core is one meaningfully modified from the previous standard, will burn rather longer, and will land on a barge downrange.
Cross-feeding fuel out of the side core tanks to the center would allow greater propulsive efficiency, as it would help to shed the weight of the side core structure and engines well before end of first stage burn. Recall that Atlas shed two of the three-initially burning engines and motored on on the center "sustaining" one (which also had a vacuum nozzle and far lower thrust, even though it looked matched at first glance). The more extravagant claims as to ultimate Falcon Heavy capabilities assume crossfeed implementation, and full expendable mode (no booster recovery).
However many references assert that SpaceX cancelled cross-feed, at least for initial Falcon Heavy. If true the difference in landing location only makes sense if either the center stage somehow has more fuel, or the center stage is run with engines substantially throttled back during at least part of the 27-engine flight phase.
The Falcon Heavy page at SpaceX specifically speaks of throttling back the center core shortly after liftoff, and does not mention crossfeed.
Regarding side core engines running at separation, some non-SpaceX material cites a plan to keep one engine in each core running a short time for trajectory control (separation assurance I suppose).
People who follow this more closely than I do assert that up-to-date Falcon Heavy details are not very available.
Marine Traffic has Go Searcher about 27km east off the entrance to Port Canaveral, as of about 1 minute ago trundling along at ~ 6 knots to the West ie. inshore. Is that the one towing OCISLY ? Too fast ? I thought it was Elsbeth III.
Cheers, Mike.
I have made this letter longer than usual because I lack the time to make it shorter ...
... and my other CPU is a Ryzen 5950X :-) Blaise Pascal
Marine Traffic has Go Searcher about 27km east off the entrance to Port Canaveral, as of about 1 minute ago trundling along at ~ 6 knots to the West ie. inshore. Is that the one towing OCISLY ? Too fast ? I thought it was Elsbeth III.
Cheers, Mike.
Elsbeth III is the tug towing the drone ship which presumably is still carrying the launching stage. And yes, 6 knots is too fast with barge in tow.
A recent forecast had the barge coming in on Tuesday.
I have just now treated myself to a bespoke 2000 piece jigsaw puzzle with this image :
.... the first re-used barrel charging upwards past the fixed gantry. The image screams rocket power and motion. For which I will assemble the puzzle and then have it mounted in a nice frame ( glue it onto a backing then glass applied to front ). I will title it Hotrod. I remember the mighty Saturn V & I am a child again. :-)
Cheers, Mike.
( edit ) A few minutes ago Elsbeth III was about 19km off to the SE of Port Canaveral entrance going ~ 2 knots and heading SW. Go Quest is nearby. Of course there is the usual large ship traffic involved.
I have made this letter longer than usual because I lack the time to make it shorter ...
... and my other CPU is a Ryzen 5950X :-) Blaise Pascal
Looking at the Port's webcam and Marine Traffic it looks like they are starting a run to bring OCISLY in now. It's a just come dawn there now, so that makes sense. I may get a look.
Cheers, Mike.
( edit ) OCISLY is well inside the port now. Someone has just rotated the camera away from viewing either the Port entrance or the SpaceX barge dock. If that's deliberate, then PTZtv ( yes, that's you ! ) will never get my money for a subscription ! Screw you too sport .... :-)
( edit ) Epic. I have a tremendous view due west/inland so that I can see the traffic on the incoming causeway ..... seriously not happy.
( edit ) On the dock there is a lady in white taking snaps due east with a long lens .... hmmm .... I wonder what of ? :-((
( edit) Now there are more people doing likewise. I can hear Elsbeth III ......
( edit ) Right. Now I'm seriously annoyed. I get a short ten seconds of OCISLY going by with, yes, that lovely booster on board. Then the camera changes to another pointing east. Nothing to see there ....
I have made this letter longer than usual because I lack the time to make it shorter ...
... and my other CPU is a Ryzen 5950X :-) Blaise Pascal
Mike Hewson wrote:As for the
)
It isn't the code that is the issue really. It is how much control it can exert. One engine failures aren't much of an issue, you just gimbal the remaining thrust a proverbial hair and it works out. Not any different than what is required for high altitude winds to stay on course. Multi engine failures begin to get more interesting. That might get to be more than the engine gimbals have available. Then you get into a situation where you have to reduce thrust to a working engine. How much, if at all, you can do that before you get to an abort into the water will depend on the flight and heft.
The code doesn't care about the limits while flying. It just drives the controls until they hit their stops. If that isn't enough to control the candle, then other software initiates an abort as the craft veers out of the flight path over the safety limits.
I wonder though if he is doing flight path control on the up phase with engine throttle. It might be reasonable to expect that you want 100% from every engine that runs all the time to try and get the customer into orbit, even if not all the way up. Of course you throttle to keep max q under load limits, but the rest of the time you want all the oomph you can get until MECO time.
Of course engine failures impact how long you have to burn the remaining engines. The existing flight control software has to calculate all of this now. The extension isn't so much writing something that doesn't exist as much as plugging in new engineering constants. Don't forget that the flight software has to be able to be pad updated for the exact amount of fuel load right up until engine start.
Not what I was referring to.
)
Not what I was referring to. The flight path isn't the interesting primary constraint. The key problem, or you don't get anything to any orbit at all, is preventing the craft destroying itself by loss of linkages b/w the cores ( eg. Space Shuttle ). I'd say the big risk is due to sudden asymmetric shears forces b/w barrels when engine is lost ( worst case is outer of side Falcon 9 ).
Cheers, Mike.
I have made this letter longer than usual because I lack the time to make it shorter ...
... and my other CPU is a Ryzen 5950X :-) Blaise Pascal
That, well that isn't code,
)
That, well that isn't code, that is metal, heavy stuff you don't want to lift but are forced to. The trade off is simple, if you lose X engines you aren't going to make it up, your metal doesn't have to be strong enough to hold then. Frankly the worst case is likely all engines running anyway as each side shoves hardest then. Yes a loss makes one side push more than the other but the total push available is less. The sudden stop might set up some vibrations but that's going to happen anyway at MECO when you intentionally shut them off.
BTW on the shuttle the exhaust gas melted the brace. That's an issue for a solid with a hole in the side, not an issue for a liquid.
Speaking of MECO does anyone know if he is going to keep the center running while he sheds the sides or if he is going to do a relight? Also are the sides going to be shed while still running? Or since I think I heard something about fuel cross feed is MECO for the sides going to also be MECO for the center and staging and then he will pop the stack apart and land them separately? Fuel cross feed seems a bit daft as then you have to be sure the cross feed valves close or each simply dumps the fuel you need to land and it is also a bunch of added weight.
Falcon Heavy first flight was
)
Falcon Heavy first flight was described by Elon as currently planned to involved the two side cores being previously used boosters which will land back at the Cape, while the central core is one meaningfully modified from the previous standard, will burn rather longer, and will land on a barge downrange.
Cross-feeding fuel out of the side core tanks to the center would allow greater propulsive efficiency, as it would help to shed the weight of the side core structure and engines well before end of first stage burn. Recall that Atlas shed two of the three-initially burning engines and motored on on the center "sustaining" one (which also had a vacuum nozzle and far lower thrust, even though it looked matched at first glance). The more extravagant claims as to ultimate Falcon Heavy capabilities assume crossfeed implementation, and full expendable mode (no booster recovery).
However many references assert that SpaceX cancelled cross-feed, at least for initial Falcon Heavy. If true the difference in landing location only makes sense if either the center stage somehow has more fuel, or the center stage is run with engines substantially throttled back during at least part of the 27-engine flight phase.
The Falcon Heavy page at SpaceX specifically speaks of throttling back the center core shortly after liftoff, and does not mention crossfeed.
Regarding side core engines running at separation, some non-SpaceX material cites a plan to keep one engine in each core running a short time for trajectory control (separation assurance I suppose).
People who follow this more closely than I do assert that up-to-date Falcon Heavy details are not very available.
Marine Traffic has Go
)
Marine Traffic has Go Searcher about 27km east off the entrance to Port Canaveral, as of about 1 minute ago trundling along at ~ 6 knots to the West ie. inshore. Is that the one towing OCISLY ? Too fast ? I thought it was Elsbeth III.
Cheers, Mike.
I have made this letter longer than usual because I lack the time to make it shorter ...
... and my other CPU is a Ryzen 5950X :-) Blaise Pascal
Mike Hewson wrote:Marine
)
Elsbeth III is the tug towing the drone ship which presumably is still carrying the launching stage. And yes, 6 knots is too fast with barge in tow.
A recent forecast had the barge coming in on Tuesday.
I have just now treated
)
I have just now treated myself to a bespoke 2000 piece jigsaw puzzle with this image :
.... the first re-used barrel charging upwards past the fixed gantry. The image screams rocket power and motion. For which I will assemble the puzzle and then have it mounted in a nice frame ( glue it onto a backing then glass applied to front ). I will title it Hotrod. I remember the mighty Saturn V & I am a child again. :-)
Cheers, Mike.
( edit ) A few minutes ago Elsbeth III was about 19km off to the SE of Port Canaveral entrance going ~ 2 knots and heading SW. Go Quest is nearby. Of course there is the usual large ship traffic involved.
I have made this letter longer than usual because I lack the time to make it shorter ...
... and my other CPU is a Ryzen 5950X :-) Blaise Pascal
Elsbeth II is port as of a
)
Elsbeth III is port as of a half hour ago
I have made this letter longer than usual because I lack the time to make it shorter ...
... and my other CPU is a Ryzen 5950X :-) Blaise Pascal
Looking at the Port's webcam
)
Looking at the Port's webcam and Marine Traffic it looks like they are starting a run to bring OCISLY in now. It's a just come dawn there now, so that makes sense. I may get a look.
Cheers, Mike.
( edit ) OCISLY is well inside the port now. Someone has just rotated the camera away from viewing either the Port entrance or the SpaceX barge dock. If that's deliberate, then PTZtv ( yes, that's you ! ) will never get my money for a subscription ! Screw you too sport .... :-)
( edit ) Epic. I have a tremendous view due west/inland so that I can see the traffic on the incoming causeway ..... seriously not happy.
( edit ) On the dock there is a lady in white taking snaps due east with a long lens .... hmmm .... I wonder what of ? :-((
( edit) Now there are more people doing likewise. I can hear Elsbeth III ......
( edit ) Right. Now I'm seriously annoyed. I get a short ten seconds of OCISLY going by with, yes, that lovely booster on board. Then the camera changes to another pointing east. Nothing to see there ....
I have made this letter longer than usual because I lack the time to make it shorter ...
... and my other CPU is a Ryzen 5950X :-) Blaise Pascal
Mike Hewson wrote:I have just
)
Me too! Controlled chaos.