-
#1120
by
RoboGoofers
on 04 Jan, 2019 16:11
-
1. Maybe this is the speed they needed to get it fly in March/April like Elon promised. It seems mostly finished to us, but we don't know what work they have planned, there could be a lot more building to do.
it's like a house that's got the frame up and the sheeting on. it goes up so quick, but 6 months later they're still working on it.
they'll have to install a lot of cabling, sensors, electronics, etc which will take a lot of time.
-
#1121
by
niwax
on 04 Jan, 2019 16:13
-
It stands to reason (?) that if the EDL needs testing "again", then the RCS is part of that. C.f. Musk tweet
Hey @elonmusk, I had a thought cross my mind about BFR. Will it be able to launch & land in most or all weather conditions similar to how the Soyuz can launch in a blizzard? Seems like an important ability for an on schedule E2E transport and orbital refueling missions.
Yes. All-weather. ~300km/h high altitude winds. ~60km/h ground winds. It’s a beast.
Watching it land in 60km/h winds would be amazing. I hope they test that by flying the hopper while vertical and traveling at 60km/h sideways.
Wind sensitivity (and generally drag) is less critical with bigger sizes, because the cross-section grows linearly with the diameter but volume and with this mass grows with the square of it (well, depending on the shape, but generally).
And if you have wide enough landing legs and good damping you could just fly it canted against the wind vertically to touch down. RCS would help to whip it fully upright just before the legs touch the ground of course.
F9 S1 weighs about 140kg/m² on landing, SS about 210kg/m² and both have about the same Cd.
-
#1122
by
RDMM2081
on 04 Jan, 2019 16:15
-
Here's a really dumb idea about the portholes: they're literally just temporary access holes poked through the side of this structure because they can.
As many have said, this is very clearly NOT the final orbital design, just a test article with crazy margins and design/construction techniques. Maybe they needed some access holes, so they just cut some holes, and intend to "patch them up as good as needed" for the test hops.
(I also think they are more probably for RCS (new methalox thrusters, not draco/superdraco) or possible even fin/canard/brakeron/gridfin thing attachment points)
-
#1123
by
rsdavis9
on 04 Jan, 2019 16:30
-
(I also think they are more probably for RCS (new methalox thrusters, not draco/superdraco) or possible even fin/canard/brakeron/gridfin thing attachment points)
Yes methalox thrusters and fin/carnard/gridfin.
-
#1124
by
holmstar
on 04 Jan, 2019 16:31
-
Here's a really dumb idea about the portholes: they're literally just temporary access holes poked through the side of this structure because they can.
As many have said, this is very clearly NOT the final orbital design, just a test article with crazy margins and design/construction techniques. Maybe they needed some access holes, so they just cut some holes, and intend to "patch them up as good as needed" for the test hops.
(I also think they are more probably for RCS (new methalox thrusters, not draco/superdraco) or possible even fin/canard/brakeron/gridfin thing attachment points)
I was going to like your post, but I disagree with the last statement. I find it really unlikely that they will be RCS ports / attachments points. They're set up for ventilation, and either will stay that way, or be patched up later.
-
#1125
by
MizaruSpaceXNut
on 04 Jan, 2019 16:34
-
Work continued throughout the night.
Why all the hurry? Working through the holidays, night shifts... It really looks as if SpaceX wants to have something to show off at the end of the month when Dragon 2 will fly for the first time (hopefully).
Elon is not getting any younger and I think he wants to go to Mars! Paul Allen and Steve Jobs proves that
being rich is no guarantee of a long life!
-
#1126
by
holmstar
on 04 Jan, 2019 16:35
-
(I also think they are more probably for RCS (new methalox thrusters, not draco/superdraco) or possible even fin/canard/brakeron/gridfin thing attachment points)
Yes methalox thrusters and fin/carnard/gridfin.
Everyone is getting carried away with "ooh this would be neat" ideas, but the hopper doesn't need RCS, air-brakes, grid fins, or canards.
-
#1127
by
RotoSequence
on 04 Jan, 2019 16:35
-
The holes seem to be predominantly on one side, and located towards the approximate volumetric center of the ship's structure. We can probably deduce something about their intended function based around whether they're mounted so that the holes are on either side of one of the landing fins, or if they're all between said fins - or neither of the above.
-
#1128
by
IncongruousGoat
on 04 Jan, 2019 16:37
-
(I also think they are more probably for RCS (new methalox thrusters, not draco/superdraco) or possible even fin/canard/brakeron/gridfin thing attachment points)
Yes methalox thrusters and fin/carnard/gridfin.
No, probably not. Typically speaking, you want to mount RCS thrusters as far away from the center of mass as you can in order to get better torque, and these holes are in what will be the center segment of the hopper.
-
#1129
by
RoboGoofers
on 04 Jan, 2019 16:48
-
(I also think they are more probably for RCS (new methalox thrusters, not draco/superdraco) or possible even fin/canard/brakeron/gridfin thing attachment points)
Yes methalox thrusters and fin/carnard/gridfin.
No, probably not. Typically speaking, you want to mount RCS thrusters as far away from the center of mass as you can in order to get better torque, and these holes are in what will be the center segment of the hopper.
not if they're for X-Y translation or rotation about Z axis. those you would want near the COM.
-
#1130
by
holmstar
on 04 Jan, 2019 16:52
-
not if they're for X-Y translation or rotation about Z axis. those you would want near the COM.
The center of mass is going to vary depending on fuel load.
If the hopper has an RCS system (and I doubt it will for version 1), it would make the most sense to have a set of thrusters on the far ends of the ship. It can then account for whatever the current center of mass might be. With thrusters at the center
it only works it's only optimized for a particular fuel load.
Edit: technically a central set of RCS thrusters would work regardless of COM, but is probably less optimal due to a smaller lever arm.
-
#1131
by
RoboGoofers
on 04 Jan, 2019 17:04
-
not if they're for X-Y translation or rotation about Z axis. those you would want near the COM.
The center of mass is going to vary depending on fuel load. If the hopper has an RCS system (and I doubt it will for version 1), it would make the most sense to have a set of thrusters on the far ends of the ship. It can then account for whatever the current center of mass might be. With thrusters at the center it only works it's only optimized for a particular fuel load.
Edit: technically a central set of RSC thrusters would work regardless of COM, but is probably less optimal due to a smaller lever arm.
z rotation RCS near the engines would impinge on the wings, and the foil tophat doesn't look like it's designed to transfer a lot of torque. as the fuel load drops the COM will drop and RCS
(possibly) in its current position will gain effectiveness at countering yaw rotation from engine gimbaling.
also these would be huge RCS, if they are. used for big pushes, not fine adjustment. there would be secondary RCS for fine adjustment.
-
#1132
by
Cinder
on 04 Jan, 2019 17:16
-
not if they're for X-Y translation or rotation about Z axis. those you would want near the COM.
The center of mass is going to vary depending on fuel load. If the hopper has an RCS system (and I doubt it will for version 1), it would make the most sense to have a set of thrusters on the far ends of the ship. It can then account for whatever the current center of mass might be. With thrusters at the center it only works it's only optimized for a particular fuel load.
Edit: technically a central set of RSC thrusters would work regardless of COM, but is probably less optimal due to a smaller lever arm.
z rotation RCS near the engines would impinge on the wings, and the foil tophat doesn't look like it's designed to transfer a lot of torque. as the fuel load drops the COM will drop and RCS in its current position (possibly) will gain effectiveness at countering yaw rotation from engine gimbaling.
also these would be huge RCS, if they are. used for big pushes, not fine adjustment. there would be secondary RCS for fine adjustment.
Is there some heuristic to rule out RCS on the fins/legs? Wouldn't those be ideal / what outweighs such a superior location?
-
#1133
by
bocachicagal
on 04 Jan, 2019 17:17
-
I hope you do not mind some more pics. The nosecone was picked up and moved nearer the "water tank". A little flag repair was needed as half was missing this morning. Nomadd do you have it?
-
#1134
by
_mit
on 04 Jan, 2019 17:21
-
not if they're for X-Y translation or rotation about Z axis. those you would want near the COM.
The center of mass is going to vary depending on fuel load. If the hopper has an RCS system (and I doubt it will for version 1), it would make the most sense to have a set of thrusters on the far ends of the ship. It can then account for whatever the current center of mass might be. With thrusters at the center it only works it's only optimized for a particular fuel load.
Edit: technically a central set of RSC thrusters would work regardless of COM, but is probably less optimal due to a smaller lever arm.
z rotation RCS near the engines would impinge on the wings, and the foil tophat doesn't look like it's designed to transfer a lot of torque. as the fuel load drops the COM will drop and RCS in its current position (possibly) will gain effectiveness at countering yaw rotation from engine gimbaling.
also these would be huge RCS, if they are. used for big pushes, not fine adjustment. there would be secondary RCS for fine adjustment.
With a minimum of four thrusters each can be angled with a different fore/aft and roll angle which would require an oval/conical inset into the porthole taking up some of the overall size. The angle of the trust vector (not simply radial) also gives a longer moment arm from the cm - this is a 9m rocket after all.
I've enjoyed following this discussion and had to jump in - not an expert at any of this just thoughts.
-
#1135
by
Nomadd
on 04 Jan, 2019 17:24
-
I hope you do not mind some more pics. The nosecone was picked up and moved nearer the "water tank". A little flag repair was needed as half was missing this morning. Nomadd do you have it?
I'm in town, eating pizza.
-
#1136
by
envy887
on 04 Jan, 2019 17:25
-
not if they're for X-Y translation or rotation about Z axis. those you would want near the COM.
The center of mass is going to vary depending on fuel load. If the hopper has an RCS system (and I doubt it will for version 1), it would make the most sense to have a set of thrusters on the far ends of the ship. It can then account for whatever the current center of mass might be. With thrusters at the center it only works it's only optimized for a particular fuel load.
Edit: technically a central set of RSC thrusters would work regardless of COM, but is probably less optimal due to a smaller lever arm.
z rotation RCS near the engines would impinge on the wings, and the foil tophat doesn't look like it's designed to transfer a lot of torque. as the fuel load drops the COM will drop and RCS in its current position (possibly) will gain effectiveness at countering yaw rotation from engine gimbaling.
also these would be huge RCS, if they are. used for big pushes, not fine adjustment. there would be secondary RCS for fine adjustment.
Both large and small RCS thruster sets are visible in previous BFS renders.
-
#1137
by
Johnnyhinbos
on 04 Jan, 2019 17:27
-
I hope you do not mind some more pics. The nosecone was picked up and moved nearer the "water tank". A little flag repair was needed as half was missing this morning. Nomadd do you have it?
Love your pics BCGal!! You know we all are "the more the merrier!"
The flag was initially affixed temporarily - because the horizontal seams that run behind it hadn't received their "cover strip". In these new photos you can see that strip has now been spot welded in place, so the flag can become permanent. Wonder how they'll do the SpaceX logo AND what they'll do for a BFS logo (instead of the Falcon 9 / Heavy).
-
#1138
by
envy887
on 04 Jan, 2019 17:28
-
I hope you do not mind some more pics. The nosecone was picked up and moved nearer the "water tank". A little flag repair was needed as half was missing this morning. Nomadd do you have it?
We never mind more pics!
-
#1139
by
Johnnyhinbos
on 04 Jan, 2019 17:30
-
Also - that center section is fully scaffold-ed on the inside, you can see the blue staging poking out of the top. That is interesting because whatever they are doing inside it, it required full height.