10 ms·

Falcon 9 attempts ocean platform landing

268 points by butwhy 12y ago

iandanforth 12y ago
Can anyone shed more light on how the "four hypersonic grid fins" work? Why are they grids and not very small fins?
- Alain-lf 12y ago
  They are low profile since they can be folded against the body of a missile/rocket. They also have good aerodynamic properties at hypersonic speeds. http://en.wikipedia.org/wiki/Grid_fin http://en.wikipedia.org/wiki/Grid_fin for more info
- deleted 12y ago
  [deleted]
- ChuckMcM 12y ago
  Watching their example video I'm guessing they act as steerable "fins" where the working area of the fin is spread across a number of "vanes". Not clear if there are two degrees of freedom or just one for each one. As the rocket travels through the air each one can be rotated on its axis perpendicular to the body of the rocket. If all are rotated the same way they would impart a spin, if two were rotated one way and other two rotated the opposite direction they would simply slow the rocket down. If two adjacent ones are counter rotated the provide drag on one side (imparting a pitch change). I was thoroughly impressed when I saw the video, that is a really cool technique.
  - mitchty 12y ago
    On the second video they show them gimbaling towards the rocket and down as well as rotating so I think they have at least 2 degrees of freedom to aide in control alongside the engine gimbal.
- colechristensen 12y ago
  * Grid fins work well at subsonic and high super sonic speeds (but poorly around Mach 1) lowering drag at high mach numbers. * Grid fins require less structure to support / actuate them per unit control force * Grid fins are more easily stowed (unneeded during launch, would cause significant drag forces if not stowed)
- VLM 12y ago
  An interesting mental model is a biplane (well, a grid of 20 not just 2) of really small leading edge slats. That's obviously not exactly how they work, but for seven word summary, not bad. They're originally a "Russian thing", for a decade or so it seemed like every missile they designed had grid fins. They're an example of high optimization. Around certain speeds they work REALLY well and weigh practically nothing and the control forces are very low. On the other hand they're little more than speedbrakes around other airspeeds.
- martythemaniak 12y ago
  Here's a Falcon 9R flight using the grid fins: https://www.youtube.com/watch?v=DgLBIdVg3EM https://www.youtube.com/watch?v=DgLBIdVg3EM
  - josefresco 12y ago
    On a completely unrelated side note; the cattle grazing (or running?) in the foreground was quite a contrast to the modern, huge rocket landing itself in the background.
annapurna 12y ago
"During previous attempts, we could only expect a landing accuracy of within 10km. For this attempt, we’re targeting a landing accuracy of within 10 meters." I thought previous landing accuracy was more than 10km. Regardless, it's highly impressive that they are working to improve the accuracy by 1000x. I'm curious if this accuracy improvement is a combination of the grid fins and the autonomous spaceport drone ship (with the ship constantly communicating with the Falcon to be an "easier" target).
- smackfu 12y ago
  It could also be a matter of "expected" vs "actual."
FD3SA 12y ago
The SpaceX launch manifest states that their next mission is Dec. 16, and hasn't been updated to reflect their schedule change to Dec. 19th: http://spacexstats.com/mission.php?launch=19 http://spacexstats.com/mission.php?launch=19 I know I'll be glued to the livecast for this one. If this works, it'll be the greatest (early) Christmas present of all time.
marak830 12y ago
Wow. I really hop they nail this landing (if not this timw then next time). A very interesting read, ill have to make a calendar entry tobkeep an eye on the news!
sparkzilla 12y ago
Stupid question probably: Why are they trying to land it on a tiny barge in the sea, instead of trying to land on land?
- AdamTReineke 12y ago
  I assume to get the accuracy down. Once they prove they can hit that target reliably, they'll be trusted to try over land (where missing can have much bigger consequences).
- Tuna-Fish 12y ago
  Because if they fail badly and the rocket slams down hard, the remaining fuel and oxidizer in the tank is going to blow up like a very respectably sized bomb. It won't quite demolish a city block, but you certainly don't want to be anywhere near it. Until they can be sure they can reliably control it during descent, they are choosing their landing sites so that even in the very worst case, it can't come down on top of someone. This pretty much means it has to come down in the Atlantic.
  - FrojoS 12y ago
    In addition to this, it will be required for the middle booster of the Falcon Heavy, which has its first flight next year and which will be too far away from land at separation for a boost back.
- softbuilder 12y ago
  I can think of several reasons, but the most significant is that the launch takes place over the ocean.
- colechristensen 12y ago
  If they don't have the precision to land on a tiny barge at sea (in calm seas), they don't have the precision to safely land anywhere reasonable. The worst case with a botched ground landing is something like dropping a blockbuster on a random, possibly populated area. The FAA won't allow them to attempt a non-sea landing until they've demonstrated several sea landings (along with much technical documentation).
curiously 12y ago
curious why don't they deploy parachutes or floatables and then slowly do a controlled descent using the rockets? I mean is this most efficient way of landing the rocket, essentially going backwards on re-entry? What if the rocket catches a gust of wind and flips on its side? Bad weather?
- thomas11 12y ago
  One reason, according to Elon Musk, is that parachutes or floatables won't work in the thin atmosphere of Mars. So if Mars is the vision, they must develop something that works there.
- danielweber 12y ago
  Parachutes are hard and have their own failure modes. IIRC even emergency parachutes have taken out some test rockets when they weren't supposed to have been deployed at all.
- simonh 12y ago
  SpaceX did try parachutes at first, but there were too many down sides. Parachutes impart heavy stresses on the rocket so aside form the weight of the 'chutes you have to strengthen the rocket, adding even more weight. They also don't allow for landings that are either precise or vertical. In theory you could use 'chutes to slow the rocket for part of the descent, but to land vertically at a precise point you'd still have to add legs and use fuel for a propulsive landing. At which point the 'chutes are adding very little value. Landing in the sea with floatables means you get a very wet rocket contaminated with saltwater and potentialy flotsam. Seawater plays havock with the hot precision metal parts of the rocket engine. Also again you have to strengthen the rocket to survive the tumble into the sea and wave action. So using parachutes adds significantly more weight without giving you what you want, and ditching into the sea also means more structural weight and mucks up your engines.
- InclinedPlane 12y ago
  For exactly the same reason that doesn't happen when landing an airplane, it's not efficient, it's complex, it's error prone. Parachutes means you have a recovery zone not a precision landing. Efficiency is all about operational efficiency, and fuel is the cheapest thing in the whole system. Burning a little fuel so that you can have a fully powered, highly controlled, high precision landing means that you are able to recover tens of millions of dollars of spacecraft reliably, and that's far more important than saving a few dollars in fuel. Precisely the same reason why airplanes do powered landings even though they have wings and it would be far, far easier for them to coast to a landing without using parachutes or whatnot. As for wind, the rocket isn't going to be launched if there's a risk of high wind gusts regardless, and most anything else the vehicle is capable of compensating for with its thrust and fins.
iamcreasy 12y ago
Anyone knows if we can see the retropropulsion form Florida coast via naked eye?
- rplnt 12y ago
  Since they haven't managed to properly film any of the ocean landings, I highly doubt it. But this time we could have good video from the platform itself.
- ceejayoz 12y ago
  Not a chance. Here's the map: https://mapsengine.google.com/map/u/0/viewer?mid=zp15b_P5ERVk.koWeOnV6-O-o https://mapsengine.google.com/map/u/0/viewer?mid=zp15b_P5ERV...
annythesillicat 12y ago
Will we see the barge landing live on webcast?
- andygates 12y ago
  r/spacex think almost certainly not - it's definitely going to be filmed and usually that footage gets released, but previous cams on the test stages didn't transmit live. The actual mission's likely to get the livestream. OTOH, it would be incredibly cool to cut to the barge and a dainty, Gernsbackian landing. So, who knows?
  - smackfu 12y ago
    This is where you can really tell that SpaceX is a private company. If something has a chance of going wrong, and they can avoid live-streaming it, they will.
techdragon 12y ago
Damn I can't wait for this. Its going to be great. Will be interesting to see how the grid fins go. I'm wondering if there could be any trouble from generating too much load from drag while they are in supersonic flow as opposed to high subsonic flow and hypersonic flow where they are known to work fine. If i were to guess, I would imagine they are going to deploy the fins after or during the 2nd burn / the retro propulsion burn, so that they can only open them after the reach their target speed. Course I'm probably wrong since I have no idea just where in the powered return flight plan they are supersonic, and they could actually be using the drag from the fins to 'slow down faster' and have engineered the fins to deal with the drag load. Which wouldn't surprise me, but will impress me if its the case.
- antubbs 12y ago
  There's been Russian military use of grid fins on supersonic rockets and missiles for many decades. It's my understanding that supersonic flow is not a problem, rather transonic (mercifully a relatively short period on either an accelerating or decelerating rocket) behavior is the problem.
anseljh 12y ago
Hilarious watching neighboring cows freak out at 2:26 and 4:23 of the grid fin test video.
- HackinOut 12y ago
  Well not your regular cows, they surely belong to a spacex farmer! :D http://www.spacex.com/careers/position/5749 http://www.spacex.com/careers/position/5749
  - riffraff 12y ago
    wait, why would they need this? Is this a joke I'm not getting?
    - prawn 12y ago
      Discussion here: https://news.ycombinator.com/item?id=8679855 https://news.ycombinator.com/item?id=8679855
      - riffraff 12y ago
        awesome, thanks.
    - jccooper 12y ago
      They lease a bunch of agricultural land, and the entity they lease the land from (city of McGregor) doesn't want to ruin the land by leaving it in the hands of a bunch of rocket scientists, so they are required to hire a farmer to manage it. http://www.star-telegram.com/news/business/article4312711.html http://www.star-telegram.com/news/business/article4312711.ht...
smegel 12y ago
Can someone explain to me the value of landing a tall, cylindrical rocket vertically like this? It just seems like such an odd thing to do.
- DuskStar 12y ago
  Rockets are extremely weak in any direction other than straight up/down. The reinforcement to allow a Falcon 9 core to even lay on its side unpressurised would probably weigh more than the entire set of recovery hardware (legs, grid fins, extra rcs fuel, etc) to land vertically.
  - marktangotango 12y ago
    Falcon 9 stages are stored on their sides unpressurized, see any of the numerous roll out videos, and factory images. There are launchers that require pressurization for handling (atlas 5?) but falcon is not one. Musk has mentioned this as a cost reduction and simplification withyou respect to encumbent providers, don't have a link unfortunately.
    - outworlder 12y ago
      Yeah. But storing and gently moving are one thing. Flying and landing horizontally would require much more structural reinforcement.
      - XorNot 12y ago
        Bingo it's all about dynamic pressure: to be reusable the hull of the rocket has to land intact and not having undergone plastic deformation of any kind, so it's as close to "factory condition" as possible.
- dshankar 12y ago
  The point is reusability. Reusable rockets will dramatically lower the cost of rocket launches. (On the other hand, if you're questioning why rockets are tall & cylindrical, it's because that's the best design for rockets: https://www.quora.com/Spacecraft/Why-are-rockets-tall-and-slender https://www.quora.com/Spacecraft/Why-are-rockets-tall-and-sl...)
RoboTeddy 12y ago
What portion of the fuel in the rocket is burned to slow down and land?
- duskwuff 12y ago
  Very little, actually. Most of the weight of the rocket is fuel; once it's hit its target altitude, it weighs practically nothing, and takes very little fuel to land.
  - motoboi 12y ago
    It weights so little that, in fact, they have to use just one engine, and throttle it down to its minimum.
- lmm 12y ago
  In all seriousness, try it in Kerbal Space Program (with one of the aerodynamic mods if you want to be more accurate); I don't have hard numbers but I'd guess something like 2-5%. Fuel needed for a particular acceleration is proportional to the mass (duh), so the amount of fuel needed for the same delta-v of an almost-empty first stage is much, much less than for one with a second stage on top.
- shasheene 12y ago
  Estimates are overall payload to orbit is reduced by around 30% with reusability. Dry land landings are more economical for SpaceX, but have further reduced payload to orbit. I understand the portion of total fuel required can be worked out from that and knowing a little about the rocket specifications.
- jccooper 12y ago
  It was said at some point to be 3%. Anywhere in 2-5% is plausible. Doesn't take much; a nearly-empty stage weighs next to nothing in comparison to a fully-loaded stack. In fact, even with only one engine at minimum throttle, the the F9R-1 stage still has a thrust significantly higher than its weight. Thus the "hover-slam" description of their landing mode: they try to slow down to just above 0 at just the right altitude. Quite a bit of precision required.
italophil 12y ago
I always wonder how much fuel this rocket needs for landing and if this reduces the maximum payload compared to the disposable Falcon 9. Find they ever release that information?
- avian 12y ago
  > In order to make the Falcon 9 reusable and return to the launch site, extra propellant and landing gear must be carried on the first stage, requiring around a 30 percent reduction of the maximum payload to orbit in comparison with the expendable Falcon 9. From https://en.wikipedia.org/wiki/SpaceX_reusable_launch_system_development_program#Economic_issues https://en.wikipedia.org/wiki/SpaceX_reusable_launch_system_...
  - madaxe_again 12y ago
    But the point is that by making the stage re-usable, you significantly cut your cost/kg, meaning that even with a decreased capacity it's more cost effective, as you could do several launches rather than just one to lift whatever. Of course, also bear in mind that this isn't technology just for the Falcon 9 - this is the test-bed. Once we have the systems in place for a reusable first stage, this can be applied to the heavy (which of course uses falcon 9's), and other future generations of craft. Until we've got SSTO spaceplanes or space elevators, this is pretty much as good as it gets.
- jccooper 12y ago
  They have said it takes about 3% of the stage's propellant load. They further say recovery systems (mostly legs and fins) and propellant reduces orbital payload by about 30%, but that their advertised capacity is already 30% under maximum performance to allow them the margin to experiment with recovery systems. The numbers are all kind of old and fuzzy, but should give you the idea. http://en.wikipedia.org/wiki/SpaceX_reusable_launch_system_development_program http://en.wikipedia.org/wiki/SpaceX_reusable_launch_system_d...
phkahler 12y ago
Its very interesting how they get to use commercial flights to do landing tests. If 50 years from now rockets are reusable and there is competition, they'll be depending on the cost saving of reuse. Any new competitor will be at a significant disadvantage. It's development that is dirt cheap by todays standards, but will be considered expensive in the future.
- taf2 12y ago
  How to do it will also be easier to learn about because it would presumably be done and published either openly or as a patent. People working in the field would know how to do it lowering the barrier to entry - hopefully making the high costs to study and research today pay dividends to the rocket industry. You are correct it would increase the cost to do similar research. Hopefully though the economy of the sector will be so much larger one off rearch focused launches can be easily done with the excess capital... At least that's my hope.
  - oroup 12y ago
    SpaceX does not file patents. [1] The assumption is that the protection offered by the patent is outweighed by the downside of giving your competitor a roadmap of how you did it. My guess is that just knowing it can be done will be a huge part of enabling someone else to develop similar technology. [1] http://www.businessinsider.com/elon-musk-patents-2012-11 http://www.businessinsider.com/elon-musk-patents-2012-11
rhia 12y ago
Why is SpaceX not using a shuttle design? From a layman's perspective, having something that basically works like an aeroplane would be much easier to get reusable, or am I missing something here?
- madaxe_again 12y ago
  Because you have to haul up a great big airframe, and you need a landing strip, and you limit your configuration. With this variety of thing you can strap multiple first-stage rockets together, blast a great big payload into space, and then the first stages return safely for rapid re-use - while your payload stays up. The space shuttle had a pretty small payload bay, and only came in the one configuration - no flexibility, like this provides. Also, with a passively slowed vessel, like a shuttle, you have a huge amount of heat to dissipate, which requires thermal tiles (yet more mass and refit each launch), whereas this slows in several burns throughout re-entry, meaning that the thermal stresses are nothing like you have on a shuttle re-entry.
- AndrewHampton 12y ago
  This is for reusing the first stage of the rocket, not the bits that actually go into space.
- antubbs 12y ago
  The shuttle's promise (inexpensive frequent launches) never materialized. Instead it was an incredibly complicated and expensive system to operate, launch, service, and recover. SpaceX's approach is to take the approach that's cost-effective and simple (but no more simple than necessary) and then to try to iteratively improve it to achieve reusable spaceflight. The "works like an airplane" thing is a great strategy if the thing can take off and get to orbit like an airplane, but to this point we (humanity) have not had the technology to produce a single-stage-to-orbit reusable spaceplane. Once we have to stage it and add boosters of various sorts, it quickly has all the same problems as a "traditional" rocket, but with all of the added complexity of a space plane. The Skylon approach purports to tackle this, but at this stage is more fiction than science (funding aside, there's a long way to go). The Energia (Russian shuttle) program originally planned to have a system like the Shuttle with even more of the rocket returnable to launch site (boosters/core stage (Energia had the "main engines" on the tank rather than the orbiter)) but also abandoned that plan (and indeed the entire program, shortly thereafter).
alexggordon 12y ago
This is an absolutely huge test. Musk's entire vision for SpaceX[0] involves cheap, reusable spaceflight, simply because there’s no other way to colonize a different planet without it. According to Musk, abandoning “disposable” rocket technology would result in a 100 fold reduction of the cost of rocket launches[1]. While it might not be that significant, I fully believe than NASA could utilize the minute budget it has much better without throwing away millions of dollars of technology every launch. Based on that, landing this rocket perfectly is the proof Musk needs to show the world he can launch that rocket again in 10 hours, essentially turning rocket launches into a daily—not monthly—occurrence. Musk’s vision aside, it would be so cool to land a fucking rocking on floating object in the middle of the ocean. It’s basically a reverse missile maneuver. They’re not ramming the object, they’re just gently touching down, but with all the more accuracy. [0] http://www.space.com/25636-spacex-reusable-rocket-test-elon-musk.html http://www.space.com/25636-spacex-reusable-rocket-test-elon-... [1] http://shitelonsays.com/transcript/npc-luncheon-with-elon-musk-2011-09-29 http://shitelonsays.com/transcript/npc-luncheon-with-elon-mu... (paragraph 13)
- smackfu 12y ago
  For efficient re-usability, you need at least three things. The first is reliable launches that don't have lots of delays. The second is reliable recovery. The third is efficient readying for another launch. That last one is trickier than people think. It was the main thing that stopped shuttles from launching faster, for instance. It took months of work to verify that all the systems were as reliable as they were before launch. It will be interesting to see how SpaceX handles that.
  - antimagic 12y ago
    The shuttle is in no way comparable with the SpaceX solution. The shuttle was notoriously slow for turn around because it was a massively complicated machine that had to be man-rated. A Falcon 9 first stage is a much simpler machine. On top of that, the shuttle had to go through re-entry, with all of the G forces, and thermal shock associated with that. The Falcon 9 first stage has neither of these problems.
kurokikaze 12y ago
When will it happen? I cannot seem to find this info in the article.
- jccooper 12y ago
  Who knows? Weather and technical issues can scrub a launch, which is why they don't say in their PR materials. But it's scheduled for Friday 19 Dec. 1:22 pm. https://www.kennedyspacecenter.com/events/2014/december/launch-falcon9-crs5.aspx https://www.kennedyspacecenter.com/events/2014/december/laun...
robertfw 12y ago
One thing I have not seen - what are the plans post-landing? Has there been any information on how they plan on securing the landed booster?
- jccooper 12y ago
  I think for previous flights they've had couple of ships outfitted for stage recovery, in case they were able to pluck them out of the ocean. Presumably one of those can go pick it up off the barge. Or maybe just tie it down and tow the barge home.

268 points by butwhy 12y ago

iandanforth 12y ago

Can anyone shed more light on how the "four hypersonic grid fins" work? Why are they grids and not very small fins?

Alain-lf 12y ago
They are low profile since they can be folded against the body of a missile/rocket. They also have good aerodynamic properties at hypersonic speeds. http://en.wikipedia.org/wiki/Grid_fin http://en.wikipedia.org/wiki/Grid_fin for more info
deleted 12y ago
[deleted]
ChuckMcM 12y ago
Watching their example video I'm guessing they act as steerable "fins" where the working area of the fin is spread across a number of "vanes". Not clear if there are two degrees of freedom or just one for each one. As the rocket travels through the air each one can be rotated on its axis perpendicular to the body of the rocket. If all are rotated the same way they would impart a spin, if two were rotated one way and other two rotated the opposite direction they would simply slow the rocket down. If two adjacent ones are counter rotated the provide drag on one side (imparting a pitch change). I was thoroughly impressed when I saw the video, that is a really cool technique.
- mitchty 12y ago
  On the second video they show them gimbaling towards the rocket and down as well as rotating so I think they have at least 2 degrees of freedom to aide in control alongside the engine gimbal.
colechristensen 12y ago
* Grid fins work well at subsonic and high super sonic speeds (but poorly around Mach 1) lowering drag at high mach numbers. * Grid fins require less structure to support / actuate them per unit control force * Grid fins are more easily stowed (unneeded during launch, would cause significant drag forces if not stowed)
VLM 12y ago
An interesting mental model is a biplane (well, a grid of 20 not just 2) of really small leading edge slats. That's obviously not exactly how they work, but for seven word summary, not bad. They're originally a "Russian thing", for a decade or so it seemed like every missile they designed had grid fins. They're an example of high optimization. Around certain speeds they work REALLY well and weigh practically nothing and the control forces are very low. On the other hand they're little more than speedbrakes around other airspeeds.
martythemaniak 12y ago
Here's a Falcon 9R flight using the grid fins: https://www.youtube.com/watch?v=DgLBIdVg3EM https://www.youtube.com/watch?v=DgLBIdVg3EM
- josefresco 12y ago
  On a completely unrelated side note; the cattle grazing (or running?) in the foreground was quite a contrast to the modern, huge rocket landing itself in the background.

annapurna 12y ago

"During previous attempts, we could only expect a landing accuracy of within 10km. For this attempt, we’re targeting a landing accuracy of within 10 meters." I thought previous landing accuracy was more than 10km. Regardless, it's highly impressive that they are working to improve the accuracy by 1000x. I'm curious if this accuracy improvement is a combination of the grid fins and the autonomous spaceport drone ship (with the ship constantly communicating with the Falcon to be an "easier" target).

smackfu 12y ago
It could also be a matter of "expected" vs "actual."

FD3SA 12y ago

The SpaceX launch manifest states that their next mission is Dec. 16, and hasn't been updated to reflect their schedule change to Dec. 19th: http://spacexstats.com/mission.php?launch=19 http://spacexstats.com/mission.php?launch=19 I know I'll be glued to the livecast for this one. If this works, it'll be the greatest (early) Christmas present of all time.

marak830 12y ago

Wow. I really hop they nail this landing (if not this timw then next time). A very interesting read, ill have to make a calendar entry tobkeep an eye on the news!

sparkzilla 12y ago

Stupid question probably: Why are they trying to land it on a tiny barge in the sea, instead of trying to land on land?

AdamTReineke 12y ago
I assume to get the accuracy down. Once they prove they can hit that target reliably, they'll be trusted to try over land (where missing can have much bigger consequences).
Tuna-Fish 12y ago
Because if they fail badly and the rocket slams down hard, the remaining fuel and oxidizer in the tank is going to blow up like a very respectably sized bomb. It won't quite demolish a city block, but you certainly don't want to be anywhere near it. Until they can be sure they can reliably control it during descent, they are choosing their landing sites so that even in the very worst case, it can't come down on top of someone. This pretty much means it has to come down in the Atlantic.
- FrojoS 12y ago
  In addition to this, it will be required for the middle booster of the Falcon Heavy, which has its first flight next year and which will be too far away from land at separation for a boost back.
softbuilder 12y ago
I can think of several reasons, but the most significant is that the launch takes place over the ocean.
colechristensen 12y ago
If they don't have the precision to land on a tiny barge at sea (in calm seas), they don't have the precision to safely land anywhere reasonable. The worst case with a botched ground landing is something like dropping a blockbuster on a random, possibly populated area. The FAA won't allow them to attempt a non-sea landing until they've demonstrated several sea landings (along with much technical documentation).

curiously 12y ago

curious why don't they deploy parachutes or floatables and then slowly do a controlled descent using the rockets? I mean is this most efficient way of landing the rocket, essentially going backwards on re-entry? What if the rocket catches a gust of wind and flips on its side? Bad weather?

thomas11 12y ago
One reason, according to Elon Musk, is that parachutes or floatables won't work in the thin atmosphere of Mars. So if Mars is the vision, they must develop something that works there.
danielweber 12y ago
Parachutes are hard and have their own failure modes. IIRC even emergency parachutes have taken out some test rockets when they weren't supposed to have been deployed at all.
simonh 12y ago
SpaceX did try parachutes at first, but there were too many down sides. Parachutes impart heavy stresses on the rocket so aside form the weight of the 'chutes you have to strengthen the rocket, adding even more weight. They also don't allow for landings that are either precise or vertical. In theory you could use 'chutes to slow the rocket for part of the descent, but to land vertically at a precise point you'd still have to add legs and use fuel for a propulsive landing. At which point the 'chutes are adding very little value. Landing in the sea with floatables means you get a very wet rocket contaminated with saltwater and potentialy flotsam. Seawater plays havock with the hot precision metal parts of the rocket engine. Also again you have to strengthen the rocket to survive the tumble into the sea and wave action. So using parachutes adds significantly more weight without giving you what you want, and ditching into the sea also means more structural weight and mucks up your engines.
InclinedPlane 12y ago
For exactly the same reason that doesn't happen when landing an airplane, it's not efficient, it's complex, it's error prone. Parachutes means you have a recovery zone not a precision landing. Efficiency is all about operational efficiency, and fuel is the cheapest thing in the whole system. Burning a little fuel so that you can have a fully powered, highly controlled, high precision landing means that you are able to recover tens of millions of dollars of spacecraft reliably, and that's far more important than saving a few dollars in fuel. Precisely the same reason why airplanes do powered landings even though they have wings and it would be far, far easier for them to coast to a landing without using parachutes or whatnot. As for wind, the rocket isn't going to be launched if there's a risk of high wind gusts regardless, and most anything else the vehicle is capable of compensating for with its thrust and fins.

iamcreasy 12y ago

Anyone knows if we can see the retropropulsion form Florida coast via naked eye?

rplnt 12y ago
Since they haven't managed to properly film any of the ocean landings, I highly doubt it. But this time we could have good video from the platform itself.
ceejayoz 12y ago
Not a chance. Here's the map: https://mapsengine.google.com/map/u/0/viewer?mid=zp15b_P5ERVk.koWeOnV6-O-o https://mapsengine.google.com/map/u/0/viewer?mid=zp15b_P5ERV...

annythesillicat 12y ago

Will we see the barge landing live on webcast?

andygates 12y ago
r/spacex think almost certainly not - it's definitely going to be filmed and usually that footage gets released, but previous cams on the test stages didn't transmit live. The actual mission's likely to get the livestream. OTOH, it would be incredibly cool to cut to the barge and a dainty, Gernsbackian landing. So, who knows?
- smackfu 12y ago
  This is where you can really tell that SpaceX is a private company. If something has a chance of going wrong, and they can avoid live-streaming it, they will.

techdragon 12y ago

Damn I can't wait for this. Its going to be great. Will be interesting to see how the grid fins go. I'm wondering if there could be any trouble from generating too much load from drag while they are in supersonic flow as opposed to high subsonic flow and hypersonic flow where they are known to work fine. If i were to guess, I would imagine they are going to deploy the fins after or during the 2nd burn / the retro propulsion burn, so that they can only open them after the reach their target speed. Course I'm probably wrong since I have no idea just where in the powered return flight plan they are supersonic, and they could actually be using the drag from the fins to 'slow down faster' and have engineered the fins to deal with the drag load. Which wouldn't surprise me, but will impress me if its the case.

antubbs 12y ago
There's been Russian military use of grid fins on supersonic rockets and missiles for many decades. It's my understanding that supersonic flow is not a problem, rather transonic (mercifully a relatively short period on either an accelerating or decelerating rocket) behavior is the problem.

anseljh 12y ago

Hilarious watching neighboring cows freak out at 2:26 and 4:23 of the grid fin test video.

HackinOut 12y ago
Well not your regular cows, they surely belong to a spacex farmer! :D http://www.spacex.com/careers/position/5749 http://www.spacex.com/careers/position/5749
- riffraff 12y ago
  wait, why would they need this? Is this a joke I'm not getting?
  - prawn 12y ago
    Discussion here: https://news.ycombinator.com/item?id=8679855 https://news.ycombinator.com/item?id=8679855
    - riffraff 12y ago
      awesome, thanks.
  - jccooper 12y ago
    They lease a bunch of agricultural land, and the entity they lease the land from (city of McGregor) doesn't want to ruin the land by leaving it in the hands of a bunch of rocket scientists, so they are required to hire a farmer to manage it. http://www.star-telegram.com/news/business/article4312711.html http://www.star-telegram.com/news/business/article4312711.ht...

smegel 12y ago

Can someone explain to me the value of landing a tall, cylindrical rocket vertically like this? It just seems like such an odd thing to do.

DuskStar 12y ago
Rockets are extremely weak in any direction other than straight up/down. The reinforcement to allow a Falcon 9 core to even lay on its side unpressurised would probably weigh more than the entire set of recovery hardware (legs, grid fins, extra rcs fuel, etc) to land vertically.
- marktangotango 12y ago
  Falcon 9 stages are stored on their sides unpressurized, see any of the numerous roll out videos, and factory images. There are launchers that require pressurization for handling (atlas 5?) but falcon is not one. Musk has mentioned this as a cost reduction and simplification withyou respect to encumbent providers, don't have a link unfortunately.
  - outworlder 12y ago
    Yeah. But storing and gently moving are one thing. Flying and landing horizontally would require much more structural reinforcement.
    - XorNot 12y ago
      Bingo it's all about dynamic pressure: to be reusable the hull of the rocket has to land intact and not having undergone plastic deformation of any kind, so it's as close to "factory condition" as possible.
dshankar 12y ago
The point is reusability. Reusable rockets will dramatically lower the cost of rocket launches. (On the other hand, if you're questioning why rockets are tall & cylindrical, it's because that's the best design for rockets: https://www.quora.com/Spacecraft/Why-are-rockets-tall-and-slender https://www.quora.com/Spacecraft/Why-are-rockets-tall-and-sl...)

RoboTeddy 12y ago

What portion of the fuel in the rocket is burned to slow down and land?

duskwuff 12y ago
Very little, actually. Most of the weight of the rocket is fuel; once it's hit its target altitude, it weighs practically nothing, and takes very little fuel to land.
- motoboi 12y ago
  It weights so little that, in fact, they have to use just one engine, and throttle it down to its minimum.
lmm 12y ago
In all seriousness, try it in Kerbal Space Program (with one of the aerodynamic mods if you want to be more accurate); I don't have hard numbers but I'd guess something like 2-5%. Fuel needed for a particular acceleration is proportional to the mass (duh), so the amount of fuel needed for the same delta-v of an almost-empty first stage is much, much less than for one with a second stage on top.
shasheene 12y ago
Estimates are overall payload to orbit is reduced by around 30% with reusability. Dry land landings are more economical for SpaceX, but have further reduced payload to orbit. I understand the portion of total fuel required can be worked out from that and knowing a little about the rocket specifications.
jccooper 12y ago
It was said at some point to be 3%. Anywhere in 2-5% is plausible. Doesn't take much; a nearly-empty stage weighs next to nothing in comparison to a fully-loaded stack. In fact, even with only one engine at minimum throttle, the the F9R-1 stage still has a thrust significantly higher than its weight. Thus the "hover-slam" description of their landing mode: they try to slow down to just above 0 at just the right altitude. Quite a bit of precision required.

italophil 12y ago

I always wonder how much fuel this rocket needs for landing and if this reduces the maximum payload compared to the disposable Falcon 9. Find they ever release that information?

avian 12y ago
> In order to make the Falcon 9 reusable and return to the launch site, extra propellant and landing gear must be carried on the first stage, requiring around a 30 percent reduction of the maximum payload to orbit in comparison with the expendable Falcon 9. From https://en.wikipedia.org/wiki/SpaceX_reusable_launch_system_development_program#Economic_issues https://en.wikipedia.org/wiki/SpaceX_reusable_launch_system_...
- madaxe_again 12y ago
  But the point is that by making the stage re-usable, you significantly cut your cost/kg, meaning that even with a decreased capacity it's more cost effective, as you could do several launches rather than just one to lift whatever. Of course, also bear in mind that this isn't technology just for the Falcon 9 - this is the test-bed. Once we have the systems in place for a reusable first stage, this can be applied to the heavy (which of course uses falcon 9's), and other future generations of craft. Until we've got SSTO spaceplanes or space elevators, this is pretty much as good as it gets.
jccooper 12y ago
They have said it takes about 3% of the stage's propellant load. They further say recovery systems (mostly legs and fins) and propellant reduces orbital payload by about 30%, but that their advertised capacity is already 30% under maximum performance to allow them the margin to experiment with recovery systems. The numbers are all kind of old and fuzzy, but should give you the idea. http://en.wikipedia.org/wiki/SpaceX_reusable_launch_system_development_program http://en.wikipedia.org/wiki/SpaceX_reusable_launch_system_d...

phkahler 12y ago

Its very interesting how they get to use commercial flights to do landing tests. If 50 years from now rockets are reusable and there is competition, they'll be depending on the cost saving of reuse. Any new competitor will be at a significant disadvantage. It's development that is dirt cheap by todays standards, but will be considered expensive in the future.

taf2 12y ago
How to do it will also be easier to learn about because it would presumably be done and published either openly or as a patent. People working in the field would know how to do it lowering the barrier to entry - hopefully making the high costs to study and research today pay dividends to the rocket industry. You are correct it would increase the cost to do similar research. Hopefully though the economy of the sector will be so much larger one off rearch focused launches can be easily done with the excess capital... At least that's my hope.
- oroup 12y ago
  SpaceX does not file patents. [1] The assumption is that the protection offered by the patent is outweighed by the downside of giving your competitor a roadmap of how you did it. My guess is that just knowing it can be done will be a huge part of enabling someone else to develop similar technology. [1] http://www.businessinsider.com/elon-musk-patents-2012-11 http://www.businessinsider.com/elon-musk-patents-2012-11

rhia 12y ago

Why is SpaceX not using a shuttle design? From a layman's perspective, having something that basically works like an aeroplane would be much easier to get reusable, or am I missing something here?

madaxe_again 12y ago
Because you have to haul up a great big airframe, and you need a landing strip, and you limit your configuration. With this variety of thing you can strap multiple first-stage rockets together, blast a great big payload into space, and then the first stages return safely for rapid re-use - while your payload stays up. The space shuttle had a pretty small payload bay, and only came in the one configuration - no flexibility, like this provides. Also, with a passively slowed vessel, like a shuttle, you have a huge amount of heat to dissipate, which requires thermal tiles (yet more mass and refit each launch), whereas this slows in several burns throughout re-entry, meaning that the thermal stresses are nothing like you have on a shuttle re-entry.
AndrewHampton 12y ago
This is for reusing the first stage of the rocket, not the bits that actually go into space.
antubbs 12y ago
The shuttle's promise (inexpensive frequent launches) never materialized. Instead it was an incredibly complicated and expensive system to operate, launch, service, and recover. SpaceX's approach is to take the approach that's cost-effective and simple (but no more simple than necessary) and then to try to iteratively improve it to achieve reusable spaceflight. The "works like an airplane" thing is a great strategy if the thing can take off and get to orbit like an airplane, but to this point we (humanity) have not had the technology to produce a single-stage-to-orbit reusable spaceplane. Once we have to stage it and add boosters of various sorts, it quickly has all the same problems as a "traditional" rocket, but with all of the added complexity of a space plane. The Skylon approach purports to tackle this, but at this stage is more fiction than science (funding aside, there's a long way to go). The Energia (Russian shuttle) program originally planned to have a system like the Shuttle with even more of the rocket returnable to launch site (boosters/core stage (Energia had the "main engines" on the tank rather than the orbiter)) but also abandoned that plan (and indeed the entire program, shortly thereafter).

alexggordon 12y ago

This is an absolutely huge test. Musk's entire vision for SpaceX[0] involves cheap, reusable spaceflight, simply because there’s no other way to colonize a different planet without it. According to Musk, abandoning “disposable” rocket technology would result in a 100 fold reduction of the cost of rocket launches[1]. While it might not be that significant, I fully believe than NASA could utilize the minute budget it has much better without throwing away millions of dollars of technology every launch. Based on that, landing this rocket perfectly is the proof Musk needs to show the world he can launch that rocket again in 10 hours, essentially turning rocket launches into a daily—not monthly—occurrence. Musk’s vision aside, it would be so cool to land a fucking rocking on floating object in the middle of the ocean. It’s basically a reverse missile maneuver. They’re not ramming the object, they’re just gently touching down, but with all the more accuracy. [0] http://www.space.com/25636-spacex-reusable-rocket-test-elon-musk.html http://www.space.com/25636-spacex-reusable-rocket-test-elon-... [1] http://shitelonsays.com/transcript/npc-luncheon-with-elon-musk-2011-09-29 http://shitelonsays.com/transcript/npc-luncheon-with-elon-mu... (paragraph 13)

smackfu 12y ago
For efficient re-usability, you need at least three things. The first is reliable launches that don't have lots of delays. The second is reliable recovery. The third is efficient readying for another launch. That last one is trickier than people think. It was the main thing that stopped shuttles from launching faster, for instance. It took months of work to verify that all the systems were as reliable as they were before launch. It will be interesting to see how SpaceX handles that.
- antimagic 12y ago
  The shuttle is in no way comparable with the SpaceX solution. The shuttle was notoriously slow for turn around because it was a massively complicated machine that had to be man-rated. A Falcon 9 first stage is a much simpler machine. On top of that, the shuttle had to go through re-entry, with all of the G forces, and thermal shock associated with that. The Falcon 9 first stage has neither of these problems.

kurokikaze 12y ago

When will it happen? I cannot seem to find this info in the article.

jccooper 12y ago
Who knows? Weather and technical issues can scrub a launch, which is why they don't say in their PR materials. But it's scheduled for Friday 19 Dec. 1:22 pm. https://www.kennedyspacecenter.com/events/2014/december/launch-falcon9-crs5.aspx https://www.kennedyspacecenter.com/events/2014/december/laun...

robertfw 12y ago

One thing I have not seen - what are the plans post-landing? Has there been any information on how they plan on securing the landed booster?

jccooper 12y ago
I think for previous flights they've had couple of ships outfitted for stage recovery, in case they were able to pluck them out of the ocean. Presumably one of those can go pick it up off the barge. Or maybe just tie it down and tow the barge home.