Will SpaceX return a Falcon 9 booster to launch pad before Xmas?

It looks like it might happen. Take THAT Bezos!!

https://www.floridatoday.com/story/...ts-land-next-booster-cape-canaveral/76576142/

Landing on a pad in the ocean added too much complexity. With them shooting for land this time I bet they will get it on their first try.

Yes! I think landing on a landing pad instead of a barge at sea will make a big difference. I hope it works!

No, they won't, for a few reasons.

For one, the next launch is going to try another ASDS landing on the ocean. The article says this at the start, but then quickly blurs that over in discussing "the NEXT launch" after, meaning launch #2 once SpaceX resumes, but that does tend to read as though they are talking about the UPCOMING Return To Flight launch

They will be lucky to get off one flight before Christmas. Indeed, a LOT of KSC launches schedules for December often get pushed to the next year due to the holidays.... a lot of times anything scheduled for a launch in December that has a "burp" of a one week delay gets delayed to the next month or even later. Same thing happened last year.

BTW -"the next" launch from LC-40 after RTF, is penciled in after Christmas, nobody believes that will happen this year though

But even if they did fly the "next" flight after RTF before Christmas, and when/if they do finally get permission to land back at the Cape, they will NOT land at the "Launch Pad". The Launch Pad is at SLC-40 (and in the future, will also be launching from LC-39A where Saturn-V's and the Space Shuttle flew from). They have been preparing a LANDING site at LC-13.

In theory it wILL be easier to land on land than on the ASDS barge. But only if SpaceX has their landing software work differently than it did for the CRS-5 mission. For that one, the first to re-enter the booster using the steerable grid fins, the hydraulic fluid was used at a higher rate than expected and ran out, leaving the booster unsteered for the last part of the descent. When the rocket engine ignited to slow it down for landing, the booster was... let's say 100 feet off to the side, over water. Well, to land on the barge, the software made it pitch over to a high angle to try to land on the center of the barge, rather than in the ocean. It built up a high horizontal velocity and hit the barge while tilted at about 45 degrees. That situation was HOPELESS, the rocket did not have the capability to land safely in that situation, it does not have the kind of throttleable thrust levels or excess fuel to "hover" and maneuver daintily horizontally like a helicopter. It is a high-efficiency "suicide burn" and "hover-slam" landing with little margin for error.

Now by comparison, for a landing on land, the software could be programmed to prioritize to do a "close enough SAFE landing", where it would limit itself to not maneuvering very much horizontally, if it was going to miss the landing pad by say 100 feet. Because the concrete main landing pad is very wide (it is not a barge), and even outside that, it could land on land and probably have minimal damage to the rocket. Of course the software's #1 priority for landing back at the Cape is NOT to stray out of the LC-13 landing zone (or ditches at sea if it can't make it that far), so if it was going to miss by 1000 feet, it would have to do some extreme maneuvering to make sure it "landed" inside the LC-13 area, even if that landing was a crash.

Now, does SpaceX have the landing software modified like that, so that if it was off by 100 feet, it would accept a close enough safe landing, or is the landing software still in CRS-5's "Kamikaze" hit-center-or-BUST mode? Nobody outside of a limited number of people at SpaceX knows that.

But, part of the huge benefit of landing on land, and not at sea, is to make use of the larger landing area that is available. A landing that misses the center by 100 feet, but is SAFE, beats trying to land less than 10 feet away with a needless risk of crashing. I have to figure SpaceX is smart enough to prioritize a close enough safe landing versus trying to go for bragging rights on how close it landed to the center.

BTW - the other crash on the ASDs barge, the chain of events for that one was that a valve was a bit sticky, so the engine did not come up to thrust as quickly as it needed to. There is very little margin for error, so the rocket was lower and faster than it should have been when it reached full thrust and that complicated the landing maneuvering. Ironically it was coming down almost directly over the barge, the grid fins did their thing beautifully to have it on the right descent path.

But what I wanted to point out that that in both crashes, it was not the ocean landing that was the direct cause, it was a contributing factor. The first try, CRS-5, that would have crashed just as badly on land, if the software was programmed to try to land at the center of the pad and not allow a 100 foot error. The other crash may have been inevitable regardless of land or sea as it was coming in "fast" due to the late ignition, though perhaps if the landing software had not needed to try to land on the deck of the ASDS, a "close enough" safe landing on land might have turned out better (or it still might have busted a leg and toppled over).

So, landing on land CAN be easier, but the two crashes have not been due to the ocean landings themselves. Both times the rocket had a problem.

Image below, SLC-40 launch site at top, LC-13 landing area near bottom.

- George Gassaway

There are several articles out there that say the next attempt will be on land.

https://www.theverge.com/2015/12/1/9832206/nasa-spacex-falcon-9-ground-landing-reusable-rockets

Over the years, I've had a few "hover-slam" landings myself.

NM has lot of dry land to shoot for. White Sands Missile Range or near Las Cruces seems like a pretty wide-open spaces...

Where did Blue Origin land?

Actually, landing downrange, which means water landing in this case, has some advantages for first stage recovery. This is because propellant is not needed to reduce forward velocity and then reverse to fly back to land for Florida launchings. Of course, there is the disadvantage of landing on a small target as a rocking barge. The transportation of returning to the Cape is provided by barge and ship, which is low-tech and not as expensive.

In the case of Bezos he is going straight up on his sub-orbital flights and downrange is not a problem. One could decide on a near straight up flight for the first stage of an orbital vehicle. If this is a very steep straight-up flight, it is a lofted trajectory, which has its own special problems.

aerostadt said:

There are several articles out there that say the next attempt will be on land.

https://www.theverge.com/2015/12/1/9832206/nasa-spacex-falcon-9-ground-landing-reusable-rockets

Click to expand...

Florida Today article starts out saying:

After its next launch, SpaceX hopes to fly a*Falcon 9 booster back to a landing site on Cape Canaveral Air Force Station, making its first attempt to bring a booster down on land rather than on a platform in the*ocean.

Click to expand...

So, it is saying that the SECOND launch, SpaceX HOPES to land back at the Cape.

The article you linked to, cited that very same article and totally misinterpreted "hopes to" land, and ignores "After its next launch", to wrongly declare the next flight (the upcoming one) WILL land.

That article also cites this:

The "very exciting news" came from a NASA representative, who made the announcement today to members of the press at Kennedy Space Center in Florida. "Their plan is to try to land [the next booster] out here on the Cape-side," said Carol Scott of NASA’s Commercial Crew Program, referring to Cape Canaveral, where SpaceX typically launches from. Scott said she had recently talked about the landing plan with a SpaceX executive. SpaceX declined to confirm the news.

Click to expand...

She may have been referring to the next flight from LC-40 after Orbcomm-2, or not. Key thing is, Orbcomm-2 is NOT a NASA launch, so whatever info she has, may be more generic rather than this specific launch.

The RTF launch is Orbcomm-2, which has a NET tentative date of Dec 15th.

Everything I'm looking at says it's set to do an ocean landing on an ASDS barge. This mission logo even has a 4 leaf clover in the ocean.



FCC permits have been obtained for communications associated with the ships and ASDS barge at sea for the mission.

Most significantly there is STILL no official approval from CCAFS to land back at LC-13…. yet. That approval is expected eventually, but it's still not been granted.

I'm not saying it's impossible for this to all change, in theory they could get the permission and go for a landing at LC-13 (Landing Complex-1) for the RTF Orbcomm-2 launch. But i've not seen any solid information that has actually occurred.

Also, BTW, it does require more fuel left over, to be able to boost back to land at the Cape, than to to an ASDS barge landing. So, only flights with light enough payloads to allow that much fuel, are candidates for landings back at the Cape. However, it does turn out that many of the flights do have light enough payloads to allow doing so.

I think one of the things at play in this is the Blue Origin landing last month, even if it is a mostly apples/oranges comparison, the public and WAY too many space article writers did not get the difference. In response SpaceX may be trying to get the publicity out there about wanting to land soon at the Cape, to pressure CCAFS, the Air Force, and FAA to give a response soon about approval to land.

BTW - I have posted message on a space forum to try to get a handle on this….. if people are misinterpreting the Florida Today article, or if there actually has been a change in plans which would also mean that CCFS has granted landing approval at LC-13 / Landing Complex-1(which if CCAFS had done so, I'd expect such news to have been quite major and easily found).

UPDATE - got this reply:

It is the next (Orbcomm 2) launch that could see a landing at X1. As the article notes, it hinges on FAA and/or USAF approval. SpaceX probably needs to do its own final assessment too, and it probably depends on whether the landing site is actually going to be ready.

Click to expand...

So, this is a REAL possibility for the next launch. SpaceX has been gradually working away at the landing complex at LC-13, maybe at a leisurely pace lacking landing approval and the stand-down while preparing for Return to Flight. So it would be ironic if the got the landing approval soon but didn't try to land there because the site is not ready, there's been PLENTY of time to get to ready. And again it may be the Blue Origin Apple/Oranges landing that may have caused this "sudden" plan to land the RTF flight back at the Cape after months and months of planning for an ASDS landing at sea.

Update #2 - i've reconsidered the reply I got. They are a well respected member of the forum.... BUT I now realize they are going by that article. While I had been asking for some independent verification. So, it is still a real possibility.... but I now realize this is still not really well verified.

- George Gassaway

Something I just read elsewhere, which stressed that these dates would likely slip:

Dec 15th - Orbcomm - Return to Flight, but not a landing attempt at launch site

December 27 - SES

Jan 4 - Jason 3

Jan 8 - CRS-8 (Attempt to land at/near launch site)

FWIW - here's some images of the LC-13 area, named Landing Complex-1 by SpaceX. These are from August, IIRC. Reportedly, there is a SpaceX logo in the center of it now, but no pics.

So SpaceX is going to launch from the Cape, then return stage 1 to the cape, without taking the long way around?

That's going to require some huge amount of fuel, right? A long burn to kill the forward momentum, then create enough reverse momentum (while maintaining some sort of altitude or trajectory) to bring the launch vehicle back over the cape... Previously, it just needed enough fuel to get Stage 2 to its separation point, then provide for deceleration burns on the way down (and some for landing maneuvers). Now we're adding a complete REVERSAL of its trajectory. Seems like it might take less fuel to do a partial orbit, but this is my uninformed lay-perspective.

What am I missing here? Can the vehicle really carry enough fuel to reverse direction after staging? If so, it seems like it's over-built for the payloads it's carrying by a significant margin.

emckee said:

So SpaceX is going to launch from the Cape, then return stage 1 to the cape, without taking the long way around?

That's going to require some huge amount of fuel, right? A long burn to kill the forward momentum, then create enough reverse momentum (while maintaining some sort of altitude or trajectory) to bring the launch vehicle back over the cape... Previously, it just needed enough fuel to get Stage 2 to its separation point, then provide for deceleration burns on the way down (and some for landing maneuvers). Now we're adding a complete REVERSAL of its trajectory. Seems like it might take less fuel to do a partial orbit, but this is my uninformed lay-perspective.

What am I missing here? Can the vehicle really carry enough fuel to reverse direction after staging? If so, it seems like it's over-built for the payloads it's carrying by a significant margin.

Click to expand...

Something to keep in mind is that after staging, the Falcon-9 is a LOT lighter! It not only does not have the mass of the upper stage and payload, it also does not have the mass of 90% to 94% of the fuel it had at liftoff. So, it does not require nearly as much fuel to do a "boost back" and land vertically as it does to take off and fly downrange to the point (and velocity) where it stages.


https://en.wikipedia.org/wiki/SpaceX_reusable_launch_system_development_program


Here's an example I ran across. It might not be totally accurate but gets across the idea:

If we're going for a Downrange landing 300 km offshore, then 20 tonnes worth of fuel or ca. 6% of the total fuel mass, and a deltaV of 1.6km/s is required. But thats not cheap. In relation to the weight of the payload where the 1st stage is lost, only 80% of the capacity will be available.
However if you want the 1st stage to return all the way to the launch site, then 38 tonnes (ca. 10% of the total fuel mass in the 1st stage) and a deltaV of 2.7km/s is required, but then the payload will drop to 62% compared to the solution where the 1st stage is lost.

Click to expand...

Figure three mission types with payload masses, where the heaviest payload mass is 100%, which is the heaviest payload that the rocket can get into a given orbit.

To launch that 100% payload mass, all the fuel (100%) is needed so the 1st stage has no fuel left to try to land. This is why some of the flights this year did not try to land on the ASDS, the payload mass was too heavy to leave enough fuel to do so.

To land on an ASDS barge downrange in the ocean, 6% of the Falcon fuel needs to be used, so the payload mass can be no more than 80% to allow 6% of the fuel to be left.

To land back near the launch site, 10% of the Falcon fuel mass is needed. So, the maximum payload mass is reduced to 62%.

Thing is, that the Falcon-9 can launch a pretty heavy payload, while a lot of the possible profitable payloads for it are not anywhere near 100% of its maximum capacity. So, that is how it is practical to have enough fuel left over to land on a barge, or even land back near the launch site, if the payloads are not too heavy.

Really, it can launch a human crewed Dragon spacecraft into orbit, to fly to ISS, and still has the fuel capacity left to at least land on an ASDS barge in the ocean (The CRS resupply missions to ISS are about the same thing, minus the man-rating and assorted special equipment). I do not recall if it can land back near the launch site when flying a Dragon. I mean, imagine if, from the Apollo days, the Saturn-IB first stage could have had its thrust improved and tanks stretched 10% or so to allow it to land safely for re-use after sending a manned Apollo spacecraft on its way to orbit?

One other way to consider it is that the original Falcon-9 was shorter. Then they stretched the fuel tanks to give it more capacity. Well, when they stretched it, they were also building-in the extra fuel capacity to do landings with, at least as compared with the original payload masses the short Falcon was able to launch (and also making other mods such as attachment points for legs and throttling). With the stretched version, they not only had the potential to launch much heavier payloads, but also to re-use the booster by flying payloads not quite as heavy as the maximum to allow for the fuel (and extra mass of things like landing legs), to land it safely.

- George Gassaway

That's my question too. It seems like there would be a lot of extra fuel to kill all the velocity it's accrued. Even if they can save the booster, that seems like a LOT of fuel, weight and money.

Nate

Edit: Thanks George!

BTW - There is a VERY long thread with info about the reusable Falcon-9 here:

www.rocketryforum.com/showthread.php?120975

So, you can find a lot of info there, as well as the previous landing attempts.

I need to update it again soon to cover this Orbcomm mission. I was going to update it once the likely launch date settled out a bit more. I'd do so now, since NET of Dec 15th is less than 2 weeks. But now I'll wait a day or two more to see how this possible RTLS landing news ends up.

I'm still not 100% convinced SpaceX is suddenly pushing to land at the Cape in 2 weeks. And that if they are, that any "leaks" to the media to try to pressure the Air Force and FAA to quickly grant permission to land may backfire.

- George Gassaway

Interesting, Thanks George.

I'd always been under the impression that the majority of the mass of the rockets was consumed by the fuel needed to lift the payload to orbit. Thus, if you have to include additional fuel for larger deltaV, you also have to include fuel to accelerate that fuel to the point that you're ready to use it. 62% max load for a return sounds like a reasonable value.

It's interesting to consider that at some point during the flight, the rocket stage will be hovering/achieve V=~0 way above the ocean. Who ever heard of making a U-turn in space? It just seems to go against everything I've been taught about efficiency, conserving your momentum and fuel use.

Very cool though.

Also consider that while the first stage is BIG and the second stage is small..... the second stage does more of the work to get into orbit than the first stage does.

A quick look for velocities came up with some numbers like Mach 6 to Mach 10 at staging (Orbit is roughly Mach 25, or about 17,500 mph). And both may be correct. Mach 10 may be the velocity for expendable flights that do not try to land the first stage, while Mach 6 may be the velocity for the landing attempts. Also, the flight path may be altered for a "lofted" course, meaning it does not curve off as horizontally as an expendable flight, trading a higher climb for some horizontal velocity.

Anyway, that means that on the flights that do try to land, they are not traveling quite so fast downrange as most would think. About 25% or so of orbital velocity.

It's interesting to consider that at some point during the flight, the rocket stage will be hovering/achieve V=~0 way above the ocean. Who ever heard of making a U-turn in space? It just seems to go against everything I've been taught about efficiency, conserving your momentum and fuel use.

Click to expand...

Well, the Space Shuttle had an abort option called Return To Launch Site, or RTLS. If an orbiter main engine shut down very early, leaving too little thrust to fly across the Atlantic to land at a contingency site, then after SRB sep the orbiter and ET would do a 180 degree turn-around, stop the horizontal velocity and fly BACK to KSC. See info from the link and drawing at the bottom.

https://en.wikipedia.org/wiki/Space_Shuttle_abort_modes#Return_To_Launch_Site_.28RTLS.29

Before the first shuttle launch, STS-1, John Young was asked why NASA was not going to do a test flight to try out RTLS. His answer was fantastic:

You don't need to practice bleeding

Click to expand...

- George Gassaway