SpaceX Falcon 9 FT - ORBCOMM-2 - Dec. 21, 2015 (Return To Flight) DISCUSSION

[Kabloona]

There has been so much discussion about the return burns, and now this from macpacheco, but there seems to be little to no credit ever given the 4 grid fins, engineering marvels in themselves

Yes, whoever thought of adding grid fins can take a good deal of credit for perfecting the landing system. Maybe Elon himself?

Maybe he read my post suggesting them from a few years back!

http://forum.nasaspaceflight.com/index.php?topic=21923.480

Hats off to you, sir! 

[AJW]

I think that we should be thanking the Russians....   This is a photo I took of the SS-20 at the entrance to the Air & Space Museum in DC.

[king1999]

Not sure how you interpret "I think we'll keep this one on the ground and just confirm through tests that it could fly again, and then put it somewhere" as saying anything other than: we won't refly this one. I think it's a waste, but people are sentimental I guess.

Yep, I think what he implied was that this stage belongs to a museum, just like the first plane from Wright brothers. Considering when the MCTs regularly fly between Earth and Mars in a few decades, this is really a significant historic piece.

[QuantumG]

I think what he implied was that this stage belongs to a museum, just like the first plane from Wright brothers.

Flyer was flown until it was broken and not easily repaired, then they moved onto the New Flyer and did the same. That's a fitting end.. the museum can reassembly the pieces.

[Kabloona]

I think that we should be thanking the Russians....

Apparently so:

Grid fins have appeared on a number of Soviet missile designs since the 1970s, particularly ballistic missiles like the SS-12 'Scaleboard,' SS-20 'Saber,' SS-21 'Scarab,' SS-23 'Spider,' and SS-25 'Sickle.' These fins have also been used on Russian spacecraft including the N1 lunar rocket and the Soyuz TM-22 capsule. In the case of Soyuz, grid fins were used as emergency drag brakes. Perhaps the most recognized appearance of grid fins to date is on the Russian AA-12 'Adder' medium-range air-to-air missile.

From this informative overview of grid fins:

http://www.aerospaceweb.org/question/weapons/q0261.shtml

[king1999]

I think what he implied was that this stage belongs to a museum, just like the first plane from Wright brothers.

Flyer was flown until it was broken and not easily repaired, then they moved onto the New Flyer and did the same. That's a fitting end.. the museum can reassembly the pieces.

Well, they are still firing it, tearing it apart and examining it. Just not re-flying it over the ocean They will have a dozen more used cores to play with next year, more than the Flyers the Wrights could build.

[CyndyC]

Spaceflight101 made no pretense that fins hadn't been around before, but as far as I know w/o reading the add'l article, they were either unlatticed & fixed, or only moved in one dimension and at the same time, as in AJW's photo. The SpaceX fins not only both tilt AND rotate, they can be operated independently. The computer programming that would have to go into independent 2-dimensional operation is the real complexity.

[CyndyC]

Maybe he read my post suggesting them from a few years back!

http://forum.nasaspaceflight.com/index.php?topic=21923.480

LOL, couldn't find your post in that link to the entire thread, Rocket Science, but hilarious to see that almost 3 years ago, the last post was Jim saying, "Wrong again." I see he hasn't changed much.

[Elmar Moelzer]

If it indicates any kind of damage or the amount of fuel/lox remaining (at some/any point in flight). If the mass of Orbcomm was less than the performance of the vehicle, indicated by lots of remaining fuel, then how does that affect future GEO/performance limited S/C launches WRT landing, etc.

I think that the tank walls can be cold enough for ice to form on them without the need to be completely full. Metal is rather conductive to heat.

[Elmar Moelzer]

This is the only thing that might be called 'bending'.
I could not find any close ups of that end of the F9 FT, the v1.1 looks different.

I don't see any bending. Just slight variations in the soot.

[AJW]

Spaceflight101 made no pretense that fins hadn't been around before, but as far as I know w/o reading the add'l article, they were either unlatticed & fixed, or only moved in one dimension and at the same time, as in AJW's photo. The SpaceX fins not only both tilt AND rotate, they can be operated independently. The computer programming that would have to go into independent 2-dimensional operation is the real complexity.

I believe that if you look at the center grid in the photo, it both tilts out and rotates.  I can't say whether the rotation is independent between each grid.   Just saying that Belotserkovskiy deserves credit for their design.  Elon & Co. deserve credit for recognizing that adding grid fins would dramatically increase landing accuracy.

[llanitedave]

Maybe he read my post suggesting them from a few years back!

http://forum.nasaspaceflight.com/index.php?topic=21923.480

LOL, couldn't find your post in that link to the entire thread, Rocket Science, but hilarious to see that almost 3 years ago, the last post was Jim saying, "Wrong again." I see he hasn't changed much.

Reply #484.  What's interesting is that within the first couple of pages of that thread, back in June 2010, people were bringing up popup fins and floating platforms for landing.

[CyndyC]

Spaceflight101 made no pretense that fins hadn't been around before, but as far as I know w/o reading the add'l article, they were either unlatticed & fixed, or only moved in one dimension and at the same time, as in AJW's photo. The SpaceX fins not only both tilt AND rotate, they can be operated independently. The computer programming that would have to go into independent 2-dimensional operation is the real complexity.

I believe that if you look at the center grid in the photo, it both tilts out and rotates.  I can't say whether the rotation is independent between each grid.   Just saying that Belotserkovskiy deserves credit for their design.  Elon & Co. deserve credit for recognizing that adding grid fins would dramatically increase lading accuracy.

I see the extra piece of metal in the center below that grid, but it still looks like it has two attachment points that can't rotate. Maybe that's where the whole set of fins is attached to its internal hydraulic system? Anyway, however much the physical & mechanical properties are similar, my guess is that SpaceX would not have had access to the Russian computer programming, and that the programming is all theirs.

[watermod]

I think the double sonic boom right after touchdown is the best. Every vehicle has it's quirks and personality (I know, shuttle did it too, but way before "wheel stop"), I have a feeling this will become well known as Falcon 9's "calling card"...BUH-BANG...the Falcon has landed! Can't wait for the Falcon Heavy quadruple report.

How far inland could the sonic boom be heard?

Assuming regular reuse, is there any chance this could become a nuisance (and therefore political issue)?  Didn't the the Concorde have to adjust their routes and destinations (which created inefficiencies) given its sonic boom.

I have never heard a sonic boom so no idea what its effects could be on a community (especially the community that doesn't care about the coolness of this achievement!)

Greg,   as a young boy my parents were ex-pats working in Taichung Taiwan.   The big ROC airbase was only 4 or 5 miles from our home.   They would vertically launch F-104s on rocket assisted intercept of PRC planes.    This would cause the whole house to shake.    We learned not to poorly mount paintings or items on the walls.   Other than that it was just a few moments of intense noise.   So my guess is only people with hearing aids would have a large negative impact.

[AJW]

I think what he implied was that this stage belongs to a museum, just like the first plane from Wright brothers.

Flyer was flown until it was broken and not easily repaired, then they moved onto the New Flyer and did the same. That's a fitting end.. the museum can reassembly the pieces.

Well, they are still firing it, tearing it apart and examining it. Just not re-flying it over the ocean They will have a dozen more used cores to play with next year, more than the Flyers the Wrights could build.

It is worth noting that other than a few exceptions, museums and rocket parks are filled with rockets and missiles that have never been launched, but people still go to see them for their historical value anyway.  I believe the Gemini display at KSC is actually built on top of a retired Titan II ICBM, not an actual Gemini first stage.  I'd rather see Elon study and reuse this returned stage and if necessary put some other retired F1.1 in a museum 20 years from now to celebrate this revolution in space flight.  Maybe save the original center M1D.

[Dante80]

Here is a question.

From the telemetry data in the livestream, I get the following (I know that ITAR or other considerations may have SpaceX not reporting 100% accurate data on their telemetry stream).

1. MECO at 74km , speed a little more than 6000kph.
2. S2 start at 85km (10s later), speed a little less than 5725kph.

Thats a difference of 275kph speed. And S2 almost reached 130km altitude before it started accelerating again (almost 30s after start up, while moving at 5650kph, at total deceleration of more than 350kph).

Isn't that loss a little extreme (no idea, not a rocket scientist). ?

[deltaV]

An object in free fall straight up will slow down by 35 km/hour each second due to gravity. An object in free fall at an angle, like a rocket during staging, will slow down a bit more slowly because of trigonometry. Early in the second stage burn the acceleration is fairly low so it's plausible that gravity and thrust would approximately cancel each other  in their effect on the speed (but not the velocity vector). Overall at first glance I see no reason to doubt the correctness of the numbers you reported.

[drzerg]

i am curious is it possible to use engine out capability in landing burns? for example in situation where rocket needs 3 engine she could burn any 3 more or less opposite of them without huge rotational momentum but situation of last landing burn of single side engine dictates precise final maneuver to make at T=0 zero velocity, zero rotation and 90 angle (3+3+2 degrees of freedom). but its possible if only center of mass not too close to engines to exceeded maximum tilt angle of them for this maneuver   

[Rocket Science]

Maybe he read my post suggesting them from a few years back!

http://forum.nasaspaceflight.com/index.php?topic=21923.480

LOL, couldn't find your post in that link to the entire thread, Rocket Science, but hilarious to see that almost 3 years ago, the last post was Jim saying, "Wrong again." I see he hasn't changed much.

Reply #484.  What's interesting is that within the first couple of pages of that thread, back in June 2010, people were bringing up popup fins and floating platforms for landing.

Those were fins like Blue were using on there first stage, not the pop-out grid fins such as on MOAB. No matter, I'm just glad they are working on Falcon (I make no claim to inventing them). I was an early "barge-ologist" as well LOL... When the ocean proved to rough later on I suggested a calm "lagoon", boy did I get all kinds of "Gilligan's Island" posts after that made me laugh. It's all good were friends here on NSF including one bright chap, who's knowledge I highly respect named Jim!

[Karloss12]

Spaceflight101 made no pretense that fins hadn't been around before, but as far as I know w/o reading the add'l article, they were either unlatticed & fixed, or only moved in one dimension and at the same time, as in AJW's photo. The SpaceX fins not only both tilt AND rotate, they can be operated independently. The computer programming that would have to go into independent 2-dimensional operation is the real complexity.

I believe that if you look at the center grid in the photo, it both tilts out and rotates.  I can't say whether the rotation is independent between each grid.   Just saying that Belotserkovskiy deserves credit for their design.  Elon & Co. deserve credit for recognizing that adding grid fins would dramatically increase landing accuracy.

After the failure of SpaceX trying parachute recovery of the first F9's and before/during the initial attempts of propulsive landing, there was a debate about whether the rocket needed to emulate an arrow and have feathers/fins and even thrusters at the top.  About three quarters of the forum had the opinion that the gimbaling of the engines would be enough for an accuate landing.

Where as about a quarter of commenters thought it was simple engineering common sense that "feathers" and thrusters would be added to the top of the 1st stage.

So give the arm chair enthusiasts on this forum a little bit of credit as well.