The article reports that the first stage achieved a near zero velocity landing. Another critical marker that was achieved, which is closely related, is that the first stage's flight dynamics (i.e., pitch, roll and yaw) were correct. Previously, the first stage was destroyed because the flight dynamics were incorrect. Also, the first stage continued to report telemetry for 8 seconds after the water landing.
Does anyone know if the first stage's landing legs were successfully deployed before the water landing? These are the 4 carbon fiber and aluminum legs (each 25ft / 7.6m long) that would be used to land the stage. I know that Falcon 9 launched with them, but I don't know if they were deployed. My suspicion is that they would have attempted to deploy them as well, for verification and validation purposes.
SpaceX hasn't confirmed it, however I would assume that that would be the case. Elon has stated in the past that the legs would provide pitch stability which was missing in the last attempt to relight the first stage. Without it the first stage likely would tumble and a relight would be impossible due to the propellant being centrifuged.
If it were me I'd probably try and get an old oil rig that's headed for the scrap yard and put a large, uniform platform on it and try and land on that. If something goes terribly wrong it will happen 20 miles from anything. The majority of rigs don't bob, they either sit on the ocean floor or they're tethered down so the up and down motion that would happen when they're free is actually translated into more or less tension in the anchor cables.
I was thinking "barge" at first but if the seas were rough it'd get tossed about and make landing a disaster.
EDIT: It would probably cost millions for all the steel even at salvage value, but that's probably a lot cheaper than the insurance (if you can even buy it) for having a reusable rocket come back over land and attempt a landing, however remote the location.
I love this idea. One challenge I can imagine is that it'll be more expensive to ship the stage back to land by barge for refuelling / refurbish and relaunch. Given that land is still pretty cheap in the USA, it's probably the case that it'll be overall less expensive to just buy up whatever they need for a "Cape Canaveral 2."
I would buy it for a couple of tests and once the systems have been proven to work go ahead and scrap the rig. The idea here is that initially there are many things that could go wrong and you want to make it safe for those things to go wrong, even very badly.
Once the bugs have been worked out (if there are any) then you start bringing it back over land.
The tricky part isn't going from 2m/s down to fully stopped and stationary on a launch pad, although I'm sure that's not easy. It's making sure you're completely in control through a whole bunch of maneuvers to transition from heading up very fast to heading back down at a moderate pace to a slowly descending hover. During some of those parts of flight you'll be moving very quickly to where a small sensor lag or instability could make differences measured in miles rather than inches. By putting the whole thing out to sea you eliminate huge swathes of risk be it human life, financial, PR, whatever.
Even if you only did one rig landing and it worked you would gain huge confidence in the systems and you could potentially refuel it on the rig to some amount and fly it back to "base"
The launch trajectories they follow when launching from Cape Canaveral don't allow them to buy land for the First Stage further down from the launch site. Many launches occur at Cape Canaveral because they allow for a safe trajectory over open water, where people are less likely to be hurt in case of unexpected performance.
We still have the primary problem: If it hits a town (due to any error, such as an unforeseen destruction of a component) the human casualty would be a disaster. It's not even just the $$.
A barge would not work because it is mobile as well.
That's why they have range safety. http://en.m.wikipedia.org/wiki/Range_safety.
Basically a remote self-destruct trigger with multiple redundant data channels and possibly a self destruct on communication loss.
You will get some debris but the damage is lot more predictable than a full stage coming down.
Isn't the issue that 'range safety' isn't really a landing feature? Look at the shuttle strewn out over texas. Range safety is fine for launch (when you have control over initial trajectory and location); or for a test-flight that is retsricted to and actual missle range (or other restricted airspace).
The Shuttle had to reenter over populated areas (and didn't hit anyone, anyways). The SpaceX first stages will be returning from over water, and targeting a beachfront pad, so if it's coming towards land too fast for comfort you can just drop the debris into the water.
The way Columbia disintegrated somewhat imitates what range safety would do anyway. The whole idea is to blow the thing into little pieces which are collectively relatively harmless. You'll note that nobody on the ground was hurt by Columbia's debris.
Beyond that, the idea with range safety is to blow it up before it gets to a populated area. Not only to you break the rocket into little pieces, but you do it so that they fall down into the ocean, or on empty ground. Columbia's landing profile didn't allow this (even if it had range safety, which it didn't) but F9-R's certainly ought to, since it's returning over the same empty ocean that it launched over.
The space shuttle has range safety, but only during launch. The shuttle launches over the ocean, which allows for 'range safety' to be implemented, on the SRBs and EFT.
Since the shuttle's re-entry flightpath is not constrained to restricted airspace, destroying the shuttle orbiter deliberately would only be "range safety" in the loosest sense.
Empirical data seem to suggest Columbia began to self-destruct over the CA/AZ border before landing in a debris field scattered over (populated) west Texas. As seen from an actual destructive episode, the debris path/cone was extensive, and unlikely to be constrained to air-space designated for such purposes.
The issues about how to mitigate this problem comes down to some of the things noted in at least one other comment here--basically SpaceX would limit the re-entry flight-path to open-ocean during approach.
Even then, the question is about ballistic "backstop"/shadow of its landing site ("the beach").
These are pretty basic questions about the size and nature of the landing facility and the ballistic match of un-guided (and potentially un-aerodynamic) debris based upon whatever the realistic assumptions of velocity/altitude and response time of the system are.
The SRBs and external fuel tanks had range safety, but as I said, the Shuttle Orbiter did not. Any "self-destructing" that Columbia did was due to extreme forces induced by the atmosphere.
The willingness to fly a manned reentering Shuttle Orbiter over populated land without range safety should not be misconstrued as the willingness to drop an unmanned first stage down with engine power without range safety.
They use range safety for launches at those same locations with planned flight paths over the same ocean. I see little reason for them to not use range safety for landings.
The orbiter (re-entry vehicle) is well know to lack range safety, unlike the full space shuttle (launch system). That is clear from my earlier comments. That is not a point on which anyone is dis-agreeing.
With that out of the way, lets look at the issue at hand.
Two issues comprise range-safety and both are at play: (1) is the egineering; and (2) is the flight paths. Proper range safety requires both (1) and (2) combined. The orbiter-as-re-entry vehicle lacked both (1) and (2). Whist the shuttle launch system had them both.
Certainly space X could engineer (1) and (2) using similar techniques at launch with no issue.
The open question is simply providing for range safety for the re-entry/recovery portion of the flight. The shuttle providese little to no road-map in that regards.
Just the opposite: it illustrates some of the difficulties.[0]
Assuming an engineered solution is present (ie, pt1 above) what would the limitations on the flight-patch (ie, pt 2 above) need to be in order that the comination (1,2) together would qualify as "range safety" in the legitimate sense.[1]
The ~rough~ answer seems to be (2') needs to be kept over water/open ocean.
So, my question is more about ballistics math: what is the envelope of precision needed to keep something either (a) in the ocean; and/or (b) out of harms way if the event is triggered closer to land.
The answer to that is something the engineers at SpaceX have surely considered.
I don't know what those calculations show; it (surely) can be safely done up to some threshold.
The question then simply is "what is the threshold"?
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[0] The scale of the debris cone from a columbia's ("natually occurring") event @ 100,000+ ft is illustrative of a couple things. None of: China Lake, White Sands, and Barry Goldwater etc alone could ~readily contain such an event. We know this because all were proximate to the debbris path (ie, western CA, Southern AZ, South/Central NM).
Some outside observers' current best guess about mitigating this danger is to have the returning boost stage initially aim for water just off-shore, which leaves time to destroy it in the air if it winds up off-course. If things look good, they can then use the landing burn to divert from just off-shore to just on-shore.
FWIW, they haven't announced anything specific about range safety management, but the "Grasshopper" landing test rig was seen rehearsing such a horizontal diversion on one of its last flights.
(As to the barge, its being mobile is a feature, not a bug: they could tow it to whatever spot at sea needs the least fuel to get to after stage separation. The problems are that the barge itself may not stay level during landing, and that the rocket exhaust from even a single throttled-down engine is still likely to burn a hole in a barge.)
The empty weight of a Falcon 9 first stage is somewhere in the neighborhood of 14 tons. It would be vaguely comparable to a DC-9 crash with little fuel left in the tanks. Not quite as bad, as it's lighter (DC-9 is about 22 tons empty) and considerably less dense. So it would be a "take out a couple of houses" event if it hit the wrong spot, I think, but nothing much worse than that.
The idea is that the booster will land at its launch site and I think that they would prefer any potential aborts to be over the water.
An empty booster may have a good enough drag/lift ratio and altitude to get much of the way back by doing a slight turn and 'gliding' with a little help from the engines.
I have not heard about a west coast launch pad, but I was wondering how they planned to actually accomplish the landing. We (almost) always launch west-to-east, to take advantage of the roughly 400m/s you gain from the Earth's rotation. It wouldn't make sense to launch from the east coast and then have the boost fly back to get to land.
Vandenberg Air Force Base, in California. The first Falcon 9 v1.1 launch, for CASSIOPE, was from Vandenberg.
Here is a sign that SpaceX has at Vandenberg, implying that they intend to both launch from and land at Vandenberg: http://i.imgur.com/YW4tmkR.jpg
Vandenberg is really only useful for polar orbits, and perhaps retrograde orbits, due to it's high inclination and it's geographical relationship to the ocean.
Huh, somehow I always though the first stage would orbit the earth once and then land. I never considered that it doesn't have enought speed or fuel to do so even if forced.
If the 1st stage could make orbit, it would constitute an SSTO craft. You have to have higher ISP than kerosene and higher fuel mass fraction than aluminum can provide to do that.
Not strictly true. The Saturn V first stage could have been used as an SSTO, and it used kerosene and aluminum. The payload would be extremely small, though, so it's not worth it.
Are you familiar with Apollo 13's pogo oscillation? Money quote:
"The engine shutdown was determined to be caused by severe pogo oscillations measured at a strength of 68 g and a frequency of 16 hertz, flexing the thrust frame by 3 inches (76 mm)."
It was this close to ripping the whole rocket apart, but it managed to withstand some incredible shaking until the engine shut down.
Are you familiar with Apollo 13's pogo oscillation?
One of my friends in Houston was dealing with pogo in rockets specifically. So yes, I am familiar with pogo in general, and I had heard of it during the Apollo program.
Neat. Apollo 13's is one of my favorite little-known facts, so I thought I would mention it. They came so close to being famous for a completely different (and equally, perhaps more, catastrophic) reason.
There are many launches from Vandenberg AFB, but most of these launches will travel south over the Pacific. It is generally used for placing payloads in Polar orbits. They never launch over land for fear or casualties if something goes wrong.
> They never launch over land for fear or casualties if something goes wrong.
Yes, that's true now, but at the height of the Shuttle program, Vandenberg AFB had begun to build, and planned to use, a Shuttle launch facility. So that's a policy change, because there was a time when they were more than willing to launch something very heavy over land to their east.
That's all Vandenberg is ever used for aside from missile tests which go west[1], and there would be no reason to use it for launches to the east when you can accomplish those just as easily from Florida without the safety concerns.
[1] http://www.spacearchive.info/vafbview.htm "With the exception of the Pegasus XL, all Vandenberg AFB launches take place from the base. Minuteman III missiles climb rather steeply and head due west. Delta, Taurus, and other satellite launch vehicles fly towards the south and climb more slowly."
It would absolutely make sense to launch from the east coast and have the booster fly back to land. You still gain all the benefit of the extra speed from the Earth's rotation to help you get to orbit. The fact that you fly the first stage back home doesn't affect that at all.
Where did you get this information? As far as I can tell, the next launch is is for Orbcomm and should be to LEO.
The last two GTO launches did not have reusability test burns because SpaceX was contractually obliged to use all of their delta-v getting the satellites into a highly elliptical orbit (which would allow the satellites to use less of their fuel for the inclination change, thus extending their lifespan). As far as I know, SpaceX only agreed to these sort of terms for those two GTO launches and future GTO launches will still include reusability burn tests.
The fact that SpaceX has come so far in such a short time is amazing. I am quite confident that they will overcome any technical challenges RE: re-usable first stages
Quick correction to the article: Gwynne Shotwell is not the President & CEO, she is the President & COO. It's very well known that Elon Musk is the CEO.
If you're confident enough that you can safely bring the rocket back over land to a target location like a lake, you might as well land it on the ground. The reason these stages land in the ocean is because it's a big safe place to drop a piece of metal you don't have control of.
Does anyone know if the first stage's landing legs were successfully deployed before the water landing? These are the 4 carbon fiber and aluminum legs (each 25ft / 7.6m long) that would be used to land the stage. I know that Falcon 9 launched with them, but I don't know if they were deployed. My suspicion is that they would have attempted to deploy them as well, for verification and validation purposes.