More on Grasshopper’s “Johnny Cash hover slam” test

Saturday afternoon Elon Musk was the subject a keynote interview at the South by Southwest (SXSW) conference in Austin, Texas. It was at the conference that he showed the first video of Thursday’s test flight of SpaceX’s Grasshopper vehicle. How new was this video? “You’re the first people to see that video,” he told an audience that filled the main ballroom and an overflow room at the conference, as well as those watching online. “Even including SpaceX, apart from the video editor who just sent it to me half an hour before this.”

Musk called this test the “Johnny Cash hover slam” test, and the video itself featured Cash’s iconic “Ring of Fire” song as its soundtrack. Grasshopper flew to an altitude of 80.1 meters, according to a statement released by SpaceX while Musk was speaking, and was airborne for 34 seconds. By comparison, on its previous flight, in mid-December, Grasshopper flew to 40 meters and was aloft for 29 seconds. The landing was “its most accurate precision thus far on the centermost part of the launch pad,” according to the SpaceX statement. And, alluding to the “hover slam” aspect of the test, “at touchdown, the thrust to weight ratio of the vehicle was greater than one, proving a key landing algorithm for Falcon 9.”

“What you saw there was essentially testing the terminal guidance and landing capability of the rocket,” Musk said at SXSW. “With each successive test, we want to go higher and further and improve the technology to the point where we’re doing transitions all the way through hypersonic and back, hopefully later this year.”

Grasshopper is a technology development vehicle that is part of SpaceX’s efforts to create a reusable version of its Falcon 9 rocket. Musk emphasized the importance of reusability to lowering launch costs in his SXSW presentation. “That’s been the goal since the beginning of the company,” he said. “I think we’ve kind of got a handle on it. We’ve got a design that, in the simulations… it closes. If we can build that thing, it should work.”

18 comments to More on Grasshopper’s “Johnny Cash hover slam” test

  • sandogtom

    Most of us watched it happen live though.

  • This looks pretty good to me, steady progress, a good and stable hover, an accurate and controlled landing. Nice work SpaceX!

    Congratulations to Elon and all the engineers and others whose hard work and vision made this possible.

    Here’s a bit more background and the state of play just six months earlier. Amazingly good progress!

    • Kirk D

      Yes, Chris, that is a real good summary of what is happening there: good steady progress. Nice work, indeed.

      I enjoyed your post from six months ago. They are making quite good progress, and they began the flight test program exactly when they said they would…so good planning too.

  • Kirk D

    Which “most of us” are you referring to?

    I’ve been wondering about the value of placing a web cam on a building or tower on an adjacent landowner’s property, able to catch “live” tests on the SpaceX MacGregor test site. Seems like a good Kickstarter project to get the funds to buy the camera, internet feed, domain name, etc. plus sign a webcam lease agreement with a nearby rancher.

  • Aresia

    Once again Space X show how to do it! I wonder – is this technology really about saving money on launches or is it about landing on Mars? Maybe both. :)

  • Coastal Ron

    Each of these Grasshopper flights have used a Merlin 1D engine, since the 1C is not throttleable. Based on it’s performance so far, I’d say the launch debut of the Merlin 1D on the Falcon 9 v1.1 should also enjoy good success.

    Overall, for a company SpaceX is doing some pretty good R&D – as good or better than most countries in the field of rocketry (including NASA right now).

  • An excellent test. The obvious result a rocket stage being able to hover and land safely.

    The less obvious result proving the new Merlin 1D engine and the software and sensor suite to control it. I appreciate the opportunity to see the continuing development of this project.

    I imagine a system with retractable landing legs, I must admit the current landing rig looks pretty heavy. Did anyone notice it appearing to be smoking a bit? Was the stetson wearing manekin there for scale or to find out if it ignited?

    The results are very useful whatever comes of this test cycle.If only to sell them to Blue Origin (joke!).

    Aresia I believe that you are quite right with your rather insightful comment the results can easily be used as a foundation for the “big prize” Mars.

  • (Corrected version)

    An excellent test. The obvious result a rocket stage being able to hover and land safely.

    The less obvious result proving the new Merlin 1D engine and the software and sensor suite to control it. I appreciate the opportunity to see the continuing development of this project.
    I imagine a system with retractable landing legs is next, I must admit the current landing rig looks pretty heavy. Did anyone notice it appearing to be smoking a bit? Was the stetson wearing manekin there for scale or to find out if it ignited?
    The results are very useful whatever comes of this test cycle.If only to sell them to Blue Origin (joke!).
    Aresia I believe that you are quite right with your rather insightful comment the results can easily be used as a foundation for the “big prize” Mars.

  • I have to ask, has anybody contravened their confidentiality employment agreement?

  • Stuart

    A fascinating insider discussion, 2013 is really looking exciting.

  • Kevin

    Wow! That was awesome! Thanks so much for posting DocM.
    I have a question regarding the SpaceX reusability design that I haven’t seen addressed anywhere and I’m wondering whether any of you folk might have some ideas. I would love to hear an explanation of how the extra mass needed for reusability (fuel, legs etc) affects the payload and economics of mass delivery to orbit. From a strictly amateur basis it seems to me that the fuel mass needed to decelerate from near orbit should be the same mass needed to accelerate to that same velocity. How can this work?

    • Aresia

      NOt an expert either but I think the point here is that Musk is looking for cost efficiency, not flight efficiency. You have a rocket that can be reused several times, and there are huge savings as a result.

      But I also suspect he intends to fly one to Mars and use that as an Earth return vehicle.

    • John

      The fuel mass needed to decelerate from Mach 6 or Mach 10 is not the same as the fuel mass to get to those speeds. The rocket weighs 18,000 kg empty and carries 372,000 kg of fuel – about 20kg fuel for every kg of rocket. Going up the rocket equation works against you, you need to use fuel to lift fuel. Coming down you just need to reduce horizontal delta v, of a much lighter rocket, say carrying a fuel load approximately equal to the rocket empty weight. Slow down and your now even lighter rocket falls back to earth. Fire the engines again close to the ground and you can touch down.

  • Michael Spacex

    After seperation of the second stage and entire payload plus using up ~80-90% of its own fuel up til stage seperation, the then you have no need to decelerat anything but an almost empty stage and by the last 1000 feet you basically are lifting an empty tank and it’s engines/landing gear which requires low throttle and I believe one engine at that point which only needs a thrust to mass ratio of just >1.

  • [...] joked that this flight was the “Johnny Cash hover slam,” according to an account from NewSpace Journal. Johnny Cash’s song about a “burning ring of fire” was playing in the background [...]

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