SpaceX News

[Tom Ligon]

I recall us wanting to use DGPS at Athena. Some of our receivers could use it. The catch is that the FCC is really stingy with the licenses. As I understand it, DGPS essentially makes a local fixed-location low-power GPS "satellite". Major airports have this for precision landings.

Without DGPS, using a good undithered GPS fix, coupled to a decent inertial navigational system, they ought to be able to hit 10 meter or better fixes most of the time.

There should be some non-GPS tricks on other bands that can give the needed touchdown fix. If not a GPS-like system that substitutes for DGPS, then something like an ILS beacon.

They'll get this. They've done soft "landings" and now they've done a precision landing. Now to do a soft precision landing on an actual landing pad.

If they're not cutting it close, they're throwing away payload capacity.

[D Tibbets]

.....

If they're not cutting it close, they're throwing away payload capacity.

And they did have a heavy payload (their heaviest?) due to makeup for the
lost Antares mission.

Dan Tibbets

[Maui]

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.

I'm happy and excited with the progress Spacex is making... But allow me to be cynical (it's what I do best)

Regarding comparisons to the space shuttle, one of the hints I was hopeful for with spacex is was that simple and reliable designs would offer big cost savings and ... reliability. Okay, newer tech, but not sure a comparison to the space shuttle in his regard is a good one. I also don't buy the argument that frequent anomalies keep them on their toes; I think they are like likelier to take attention from other potential issues that otherwise could get investigated/checked/addressed sooner. After all, a space shuttle team "on their toes" still lost two vehicles.

As far as the ramp up in launches last year, the fact is they launched six when they had planned for 15. Not exactly the nimble comparison to NASA and the big conclomerates I was hoping for.

But I am positive about today's outcome, and this is a new year. Excited for the next try.

[D Tibbets]

NASA on their toes? Both shuttle losses were due to management decisions to ignore or minimize known engineering issues.

Also, Space X has struggled with NASA for launch facilities and scheduling. Perhaps this was inevitable, bureaucratic, or reasonable. It has slowed the progress of the program.

Nothing is perfect, especially with rockets. Any instrumentation and procedures that catch problems before launch is good. It does slow things down, but not nearly as much as launch failures. The recognition, management and evolutionary resolution of issues is key to a successful program. The management of this evolution is what may separate private approaches like Space X from behemoths like NASA. It does not eliminate risks though, as exemplified by recent Antares problems. And, it should be pointed out that Space X lost a test "Grasshopper" rocket, not through actual rocket failure, but through a decision to reduce senser redundancy- which failure terminated the launch.

Dan Tibbets

[Maui]

NASA on their toes? Both shuttle losses were due to management decisions to ignore or minimize known engineering issues.

Exactly my point. Frequent anomalies don't keep an organization "on it toes" and, thus, safer. And you bring up another point... the more delays from anomalies, the more pressure there will be to minimize/ignore them (whether or not the organization succumbs to the pressure).

[hanelyp]

Without DGPS, using a good undithered GPS fix, coupled to a decent inertial navigational system, they ought to be able to hit 10 meter or better fixes most of the time.

For an efficient vertical approach, that kind of positioning precision sounds like a lot of very "hard" touch downs.

There should be some non-GPS tricks on other bands that can give the needed touchdown fix. If not a GPS-like system that substitutes for DGPS, then something like an ILS beacon.

Indeed, better than stock GPS is needed for final approach.

[Betruger]

Don't they use some kind of direct radio signal for guidance between ASDS and rocket stage, in addition to GPS?

[Tom Ligon]

Without DGPS, using a good undithered GPS fix, coupled to a decent inertial navigational system, they ought to be able to hit 10 meter or better fixes most of the time.

For an efficient vertical approach, that kind of positioning precision sounds like a lot of very "hard" touch downs.

There should be some non-GPS tricks on other bands that can give the needed touchdown fix. If not a GPS-like system that substitutes for DGPS, then something like an ILS beacon.

Indeed, better than stock GPS is needed for final approach.

The first time DGPS came up for us was for a precision flying "camera crane", a small UAV helicopter. One of our early control systems flew it well, but we could not position the thing reproducibly as well as the customer wanted. They wanted to put the camera within 6" of the intended position every time. We thought it would be technologically feasible with DGPS, but the legal issues would have taken a small army of FAA and FCC lawyers to work out.

And that's still going on with the whole commercial UAV broo-ha-ha, but getting closer to a resolution. This whole matter of being able to offer UAV-based aerial photography is driving the issue. Some of the little quadrotors are getting close to the technical solutions, but the legal wrangling is still ongoing.

But quadrotors are routinely touching down, as I understand it, with the precision Musk needs for his rockets.

[GIThruster]

With how tiny they can make K band radars these days I suspect they have it on the tail of the rocket. No reason to worry about DGPS if you can see the ground, and radar has no trouble distinguishing between water and the platform. Honestly we talk about hitting a 170X170' mark but I doubt you can land on the edge of the platform and not have the rocket topple over from tilting it. They need to hit close to dead center, which I suppose means looking at the platform itself. Likewise with Dragon docking with ISS--I think it uses a laser rangefinder but there's got to be more to it than that--probably Ka band but could include mm V or even W. They build these things on chips smaller than a dime now.

[Betruger]

What's the use of that extra deck area to SpaceX if it can't be landed on?

[GIThruster]

The wider the barge is, the more stable it is to unbalanced loading.

[Maui]

http://spaceflightnow.com/2015/01/11/ph ... k-in-port/

Looking at the pics of the returning platform, I would have guessed the problem was not hard landing, but non-centered landing (which it seems to me might be better explained by a lack of hydraulic fluid than a hard landing).

But I guess really almost anything could have happened once it hit the deck and broke apart...

EDIT: Actually Reddit user xinareiaz created a highly technical reconstruction of this scenario:

[D Tibbets]

The pictures do seem to indicate the rocket landed near the back left (as orientated by the direction of travel of the barge). The scorch marks on the cargo container and red and white structures in this area suggest the rocket cane down very close to this area. Either that or it tipped over and continuing rocket thrust was diverted there. Alternately, if the rocket tipped over the tube/ tanks of the rocket may have may have hit there and caused a fire. I do not see any other obvious (expected?) scortch marks on the deck from the site of touchdown though.
The rocket may have broken up from deceleration when it hit. Also, if it touched down near the shipping container/ structure on the back edge, one of the landing legs could have hit the elevated structure and resulted in the rocket tipping over and/ or uneven stress on the landing structure and torquing of the rocket that tore it apart. If hydrolic fluid depletion is stressed, that may have been the root cause of the rocket missing dead center touchdown and subsequent problems from the non flat surfaces. Or...

As for the barge tipping because of a non centered landing I doubt it is a major concern. The almost empty rocket does not weigh a lot. And if a non centered landing resulted in increased weight on one side, this would push that side pontoon deeper in the water while lifting the opposite pontoon out of the water. The non centered weight would be almost compensated for by opposite changes in buoyancy. Within limits and on a wide barge this would result in little barge tilting.

Dan Tibbets

[Skipjack]

Some people are speculating that the rocket hit the barge from the side, probably with a sideways motion. This could be due the grid fins not functioning properly.

[paperburn1]

The photos in the link are high res and blow up very well. (no pun intend)
It looks like they have landed but it fell over