Talk-Polywell.org

Ideally, the first stage flies straight back, the second stage orbits once and flies back and the capsule lands near the processing facility as well, so none of the components of the system have much terrestrial travel to pay for. . .all in TX.

Guess we'll see. . .but I'll be happy to see them land just the first stage for now.

D Tibbets wrote:

GIThruster wrote:Once they're demonstrated a bunch of safe landings I think what they want is clearance to land in TX near the refurbishment and launch facility. Then their costs drop hugely.

I suspect the Texas site could only be used for first stage landing/ recovery if the launch site is in Texas or perhaps New Mexico. The First stage can not complete anything near an orbit of the Earth. I wonder if launch from Cape Canaveral would result in East Texas being a good site for second stage landing/ recovery, if they advance that far .

Dan Tibbets

They are building a launch site in Texas.

GIThruster wrote:Ideally, the first stage flies straight back, the second stage orbits once and flies back and the capsule lands near the processing facility as well, so none of the components of the system have much terrestrial travel to pay for. . .all in TX.

Guess we'll see. . .but I'll be happy to see them land just the first stage for now.

I am not sure their second stage would have enough cross range to do a one orbit return. Also Elon Musk recently said that the current F9 will not do second stage reuse. They will instead do that for their planned future vehicles.

... and delayed ... again...

Yeah, but even traditional launches see these delays. The Shuttle was delayed about as often as these new rockets and I for one am happy Musk would choose to delay rather than push for a quick launch when he doesn't have 100% confidence. Seems the sensible thing to me.

GIThruster wrote:Yeah, but even traditional launches see these delays. The Shuttle was delayed about as often as these new rockets and I for one am happy Musk would choose to delay rather than push for a quick launch when he doesn't have 100% confidence. Seems the sensible thing to me.

They have increased their launch rate quite a bit this year. It is good to see that they are still playing it safe, with all the routine. Every now and then a small problem is a good thing. It keeps the crew on edge. Its when things get "too routine and boring" when the mistakes happen.

Advantage of Florida for space launch: lots of open ocean to the east for an expended (or failed) stage to splash down.
Disadvantage: far too many days with high wind or otherwise inclimate weather causing launch delays. This same disadvantage applies if you intend to launch from Texas and dry recover a stage in Florida.

hanelyp wrote:This same disadvantage applies if you intend to launch from Texas and dry recover a stage in Florida.

According to Musk, the stage cant make it all the way to Florida.

SpaceX

about 4 hours ago

Launch Update

During the terminal count engineers observed drift on one of the two thrust vector actuators on the second stage that would likely have caused an automatic abort. Engineers called a hold in order to take a closer look. SpaceX is scrubbed for today and we are now targeting launch on Jan. 9th at 5:09am ET.

Disappointing, but still better than an abort, or worse a failure.

https://www.facebook.com/topic/SpaceX/1 ... 5419298510

ah well, at least they got it to the pad. That's quite an accomplishment.

GIThruster wrote:https://www.facebook.com/topic/SpaceX/1 ... 5419298510

ah well, at least they got it to the pad. That's quite an accomplishment.

They ran out of hydraulic fluid; need to increase reservoir size. Effective learn-by-doing engineering. I like.

GIThruster wrote:https://www.facebook.com/topic/SpaceX/1 ... 5419298510

ah well, at least they got it to the pad. That's quite an accomplishment.

They hit a 170x170 foot target. I think it is quite an accomplishment. Proofs that they can control their vehicle with precision, especially since hitting a comparably small, moving barge precisely is much harder than a stationary and much larger landing pad on terra firma. It is not sure yet why they hit the barge harder than they wanted. It could have been because of wave action. Musk also said something about the grid fins running out of hydraulics fluid, but they did not quite say how that affected the landing to cause it to be hard. The rocket might have started spinning, driving fuel away from the pipes and causing it to run out of fuel before the final breaking burn was completed. Or it still had too much lateral motion left and no grid fins to stop that.
We will know more soon.

Final 'touch down' was hard, but apparently not a high speed crash. With hydraulics exhaustion (of guiding vanes and/ or rocket gimbals?) it's hard to say what the profile was at landing. Was it spinning, tilting, lateral drift? Did al lof the landing struts deploy? For that matter, what is the shock absorbing capacity of the landing struts?

I wonder if the guidance was all GPS. I understand there is several meters error in altitude, unless you have military codes to bypass this purposeful uncertainty. Was a radar altimeter used?

And, as mentioned, wave action- swells might make a difference in platform up and down motion by as much as several meters per second. I don't know the limits on the Falcon 9 sink/ descent rate at landing. For lunar landers, sink rates above ~ 3 M/s would exceed the landers limits (crash).

Dan Tibbets

For high precision you don't use just a GPS receiver on the vehicle. You have one on the landing platform and a radio link to tell the vehicle where the landing point is. Over a short distance a lot of the errors in GPS measurement should be near the same at both points. Differential GPS. I also understand that selective availability hasn't been in effect for several years.

Though if I were designing terminal guidance I'd use a set of beacons with known position around the desired touch down point to implement a local positioning system for terminal guidance.