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Comment by Shivetya | Hacker News Reader

Why does Space X land on barges while blue origin land, well on land. Also does anyone have a pictures of iterations of Space X's landing methods and strut setup?

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SpaceX launches stuff into earth's orbit, and to enter orbit you must be traveling very fast horizontally -- it is not enough to merely escape the earth's atmosphere by ascending vertically. The first stage travels hundreds of miles 'downrange' of the launch site (as well as up) in order to achieve the required horizontal velocity. Most orbital launches are aimed over an ocean, so that if something goes wrong the fiery bits don't land in a populated area, hence the need for a landing barge.

If the first stage were to "fly" all the way back to land after separating from the second stage, that would require some combination of a heavier/stronger rocket to hold more fuel, and a reduced payload capacity to orbit.

Blue Origin only does short, up-and-down flights -- they are not trying to achieve orbit so there is no need for horizontal travel. They can simply shut off the rocket and fall back to the launch site.

> If the first stage were to "fly" all the way back to land after separating from the second stage

You write it as a hypothetical, but that's actually how SpaceX landed their first first booster. It was Falcon 9 Flight 20, which deployed 11 Orbcomm satellites.

Infographic of the trajectory: https://i.imgur.com/D9BdO86.png

Thanks for sharing that infographic. I was literally just wishing I had some way to visualize the trajectory when I read your comment.

Interestingly, NASA also considered that as a potential abort mode for the Shuttle ("RTLS" - return to launch site). Minus the vertical landing of course. It was the first option that would be available in the event of a failure, immediately after SRB separation. The vehicle would execute a Powered Pitch-Around maneuver and then jettison the external tank, timing things so that they would run out of fuel and the vehicle would have its proper CG for gliding.

The astronauts considered it extremely risky to say the least. NASA actually wanted to try it on STS-1 (a manned flight on a system that had never been tested before) to see if it worked. In the words of the mission commander: "Let’s not practice Russian roulette, because you may have a loaded gun there." Which carries a lot of weight from a man who was willing to risk a lunar landing.

http://www.tested.com/science/space/460233-space-shuttles-co...

https://en.wikipedia.org/wiki/Space_Shuttle_abort_modes#Retu...

Previous HN discussion: https://news.ycombinator.com/item?id=8447479

Yep - it mostly depends on the available fuel left over after the orbital insertion. Not an option on all missions.

Blue Origin does not launch into orbit. Going up is the 'easy' part. To get to orbit you have to go many thousands of miles per hour sideways. Blue Origin doesn't go sideways at all, they just go up and come back down.

SpaceX has done 'land' landings in the past as well (for lighter payloads they have enough fuel to turn around and come all the way back to land).

EDIT: Here's a quick explainer on the topic with shiny graphics: http://www.popularmechanics.com/space/rockets/a18711/blue-or...

Relevant (what-if)xkcd: https://what-if.xkcd.com/58/

In this case it would have been barely possible to do a land landing, but the margin was much larger for a barge landing (since the stage doesn't have to return all the way to the launch site, which takes quite a bit of fuel). In the end it doesn't really matter, though. The cores that land on the barge just take a few days longer to return home.

Droneship landings are particularly convenient for west coast launches, as they can unload them ~20 miles from the factory (which is where they are refurbished, for now at least).

It is pretty easy to learn the difference in this with a very basic rocket in kerbal space program. Launch up and you'll come down near where you started, in a parabola... Launch up and then go sideways to gain orbital velocity for a long time, you're in orbit.

Agree, KSP is a great way to internalize how orbital mechanics work. After playing it a little while, everything clicks and things become natural, like the sort of physics one uses playing billiards or building block towers.

Others have answered your question about landing on land. So I thought I'd just link the pictures you asked for.

The initial (publicly shown) iteration was Grasshopper, it looked like this [0].

After that there was F9R-Dev, which looked like this [1] (it's pretty much just a F9 first stage). At some point they added grid fins, which look like this on the vehicle [2] and this up close [3] (note the anti-pidgeon spikes are being added purely for display, they are not attached during flight). Other than that there haven't really been any visible iterations, the legs look like this [4] and have since the F9R-Dev.

[0] http://spacenews.com/wp-content/uploads/2014/11/Grasshopper_...

[1] http://i.imgur.com/ZTpp8pP.jpg

[2] http://www.spaceflight101.net/uploads/6/4/0/6/6406961/518499...

[3] http://spaceflightnow.com/wp-content/uploads/2016/08/SPACEX-...

[4] https://i.stack.imgur.com/YXCrb.jpg

SpaceX can and will land on land when the mission allows it. See ORBCOMM-2: https://www.youtube.com/watch?v=ANv5UfZsvZQ

Blue Origin's mission allows it because it's suborbital. That is: it doesn't actually go anywhere other than straight up. That's also why they can launch in the middle of Texas.

Because SpaceX goes to orbit and Blue Origin doesn't.

One thing others haven't mentioned is that the Falcon 9 is probably something like 10x the empty mass (or more) than the vehicle Blue Origin has demonstrated. As others have said, it's also going higher and much faster, and accomplishing the landing in addition to (and secondary to) launching a real commercial payload into orbit, which AFAIK Blue Origin has never done.

Blue Origin's accomplishments (especially their engine designs) are nothing to sneeze at, but SpaceX is currently in a completely different league. The fact that they have to land on a barge is a result of how scaled and practical their technology is; that they succeed in doing so is an unprecedented achievement in launch vehicle technology.

Two issues I remember hearing - there's a much larger launch window for landing on the ocean barge and something regarding approval/ regulations being more stringent for a land launch. Blue Origin's test flight didn't go too high so it didn't face the same issues.

I may be completely wrong here but I'm fairly certain that's what I remember reading.

Yeah you're wrong, it's to do with the speed they are travelling to get the launch trajectory, they lack the fuel required to make it back to land

It has nothing to do with the height. Both rockets go 'up' a similar amount. The difference is how far sideways Falcon 9 has to go (since it is launching a payload to orbit).

https://what-if.xkcd.com/58/

Have Blue Origin gone 'up' further than ~100km ?

They're in that ballpark. I know the capsule exceeded 100km. I don't know if the first stage technically broke that or not, but it was closer if it didn't.

I think SpaceX are in a much higher ballpark?

Not really... A few dozen km altitude difference doesn't mean a whole lot. The _much_ more significant difference is that Falcon 9 is traveling sideways at several times the speed of sound. New Shepherd is "just" going sight up and coming back down.

Just to add to the discussion - Blue Origin don't land on land yet, but when they start doing orbital launches with New Glenn, they will have to.

IIRC Blue were sitting on some "landing on a barge" patents that SpaceX successfully fought, because they were far too obvious.

SpaceX has landing pads (see LZ-1 at the Cape) on land as well, and used one for a successful landing already. For the Falcon Heavy launcher there have been plans reported for two, or maybe all three, of the stage one cores to return to the launch site and land there.

They use the barge as they are firing much harder than blue origin and don't have the fuel to make it back to land

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