In fact, it is my understanding that they provide roll, pitch and yaw. I assume that it’s a combination of lift and drag effects across all four fins. If you look at the early test of the fins, they work as wings at low speeds, allowing precise control.
Here’s the Wikipedia article on grid fins.
Thanks.
Looking at them you’d not think they have such a great effect. I’ve been watching these videos wondering how something with lots of holes can affect flight. How big do you think they are, its a little hard to gauge scale sometimes with this section.
You are 100% correct I was being lazy. Thanks for the elaboration!
By the way, I’ve been meaning to tag you…there’s a current discussion on /r/spacex about using the MHD shielding for aerobraking that you linked recently. Some people have done some math to make the argument that it could allow heavier payloads while still having the ability to land. It’s really interesting! I haven’t checked the math but it appears there could be a useful case for it.
A quick examination of a photograph suggests that they’re about 1.0 x 1.2 meters on the production rockets.
The NASA paper talks about aerobraking, aerocapture and landing, but the Mars landers all just dove right into the atmosphere while still at interplanetary velocity. I find it strange that, if there is value in braking before landing, the Mars lander teams wouldn’t embrace that technique. I wonder if the actual landing phase is so energetic that the systems might as well be beefy enough to deal with the interplanetary velocity, simplifying the overall process.
After all, let’s say that an interplantary probe returns to Earth. Its interplanetary velocity can be shed and the probe will be in a nice orbit around the Earth, but you’re still left with a LEO reentry, just like any other spacecraft that uses ablative systems. That’s better than trying to deal with ablating the heat of the interplanetary velocity, but I wonder if ablative systems aren’t ultimately capable of dealing with it - as the Stardust capsule did (which reentered at 12.4 km/s, 70% faster than the Shuttle).
The grid fins on stage 1 are ~6 feet or ~1.4 meters long. They’re deceptively large.
I’m not entirely sure where your confusion lies. It may have been with my explanation though. The thread is discussing the benifets the techinique could have for stage1(and possibly stage2) reuse, due to requiring less fuel for braking which leads to more fuel to impart energy to the payload.
There isn’t much difference whether this is being done on Earth or on Mars unless I am misunderstanding your point.
SpaceX uses a proprietary PICA-X derived ablative ceramic material that is supposed to be reusable and enter at speeds from lunar or martian return trajectories. The mag-shielding tech could either improve the the lifetime of a particular shield or allow faster reentries.
If you’re talking about hypersonic retropropulsion it has never been done before until the last year or two since SpaceX began testing their reentries. It’s one of the reasons NASA is so interested in it because it’s the only way to land heavier payloads on Mars due to an upperlimit of mass that a parachute can slow down.
This is really cool so I’ll link this as it applies to hypersonic retropropulsion. It also helps you visualize the wavefront encountered when reentering the atmosphere.
Edit: To clarify, I’m unsure of the size of the gridfins on @JB47394’s video, but on the actual F9 first stage they are 6 feet long. His numbers are probably correct for F9R dev.
6 feet, yeah that is bigger than I first thought. This thing really is huge. And having those legs come out as it lands, it really a big step into space Sci-Fi, like we were promised when we were young… Well when I was young anyway. I think the next ten years are going to be very interesting for all these new projects.
What I like that Elon Musk has basically done is really drive in clearly that space exploration can be cut in cost, and that the single most important point to advancing space travel is reducing cost.
There’s a difference between something being known or easily understood and being strongly reinforced. I think that SpaceX has really strongly reinforced the idea that cost is the real factor to consider.
In terms of being an emerging technology/systems nut in terms of thinking about how technologies will affect one another, I really like the idea that computation is going to increase economic productivity through computation, reducing the cost per person to actually use a rocket.
Automation will also decrease the cost of space travel further. It will make mining/forging of materials used in spaceflight cheaper. It will allow for more automation in spaceflight. It will allow for self-driving vehicles to actually transport the materials. It will allow computers to actually order and manage materials with more limited human intervention. Improvements to battery energy density and renewable energy (mainly solar) will interact with one another.
So, there’s more than just reusable rocketry happening. There is a lot of stuff that will just drive costs down across the board anyways that is in development now.
A well produced show that I listen to often. Discussing the returned stages thus far.
Hutch! You’ve been mia I was worried you snuck on to the last crs launch!
Maybe you did since it just came back last week…
I’m on to you…
inb4 we end up getting a captain america to complete the musk goal of becoming ironman.
I can’t wait for the MCT architecture unveil, F9 relaunch attempt and F Heavy launch debut.
Three more huge things to look forward to this year.
Thanks for pinging me to the thread, you’ve just reminded me!
Hey everyone there’s a launch this Wednesday! At approximately 10:32 EST or 7:32 PST falcon 9 will be launching eutal Sat and Asia Sat(I think, writing this off memory as I’m in the movie theatres right now).
Not sure of the UTC time but I’ll see y’all there on the forums and on discord!
This one is now just a “pray it doesn’t die” scenario. Lol.
With just over 12 hours to launch, here are links to the full webcast and techinical casts:
Full: https://www.youtube.com/watch?v=gLNmtUEvI5A
Technical: https://www.youtube.com/watch?v=ckjP8stlzxI
They also have a countdown to launch(The streams go live about 20 minutes before launch) to get your local countdown time.
Hasta mañana!
Hey guys, we have the first video and some information of what happened with the landing. According to Elon, the 1 engine firing during landing( after 1 -> 3 -> 1 alternation to quickly slow down to minimize losses) ran out of Liquid Oxygen to burn and abrubtly stop firing before touchdown.
The speculation is that the black smoke is caused by the RP-1 still burning as was seen as a larger fire than normal from the barge cam during the original stream.
Edit: I was paraphrasing from what I’ve read and linked the video tweet and it turns out that’s exactly what Elon said so now I’m just repeating myself…I’m trying to figure out a way to get it to play here on the forums currently.
Best I can get is that direct link, oh well, check it out it’s pretty rad!
There is a stabilized video in that tweets comments where you can see the landing better:
I think the rocket came in inaccurate from the “falling down and steering only with grid fins phase”
or they tried a different landing profile this time.
It looks like the landing burn had to kill a lot of horizontal speed first.
After that the rocket had killed also a lot of its vertical speed but was still a bit to high which looks in the video like it was hoovering a bit above the droneship - and ran out of fuel doing so…
About the black smoke. I read somewhere that this time the tipping rocket didn’t explode.
That’s why it looks different 
That video is great. You can see it starting to topple over right at the end there.
The way it slowed itself almost to a hover seemed odd at the time. I’m assuming it took too long to correct itself thus losing too much fuel.
We should also have a Blue Origin thread.
Jeff Bezos’ Blue Origin Will Webcast Rocket Launch Live On Sunday
I’m sure we will see another very slick HD video.
Maybe OP can just rename this thread. These launches aren’t frequent enough to warrant a separate thread.
Blue Origin has sturdy looking rocket.
This was from 02 April.
Only vertical up and down though, not as advanced as Space-X’s flight path.