Talk for Story "SpaceX launches world’s most powerful rocket, Tesla overshoots orbit"

Talk about this Story

  1. “MSNBC tweeted footage of the landing.”

    So what? This sentence doesn’t seem to add anything to the story.

  2. Great summary. One suggestion: “Overshoot” implies a mistake to me. I suggest replacing this term with a neutral or positive term, such as “exceeds target orbit”.

    It is my understanding that SpaceX always intended to “burn until empty” on the final burn toward Mars. As a test mission, they wanted to see how far they could get, with Mars orbit as a goal. I interpret the fact that they exceeded their goal as a positive (demonstration that they had slightly more than enough fuel to their target). This is the way real mission to Mars would be designed, except that they would have stopped the burn once they reached the velocity necessary to reach their goal.

    I don’t have any quotes from SpaceX that fully support my above interpretation, but the two quotes below seem more consistent with a positive interpretation:

    The wording from Elon Musk’s tweet is neutral-to-positive (“successful”, and “exceed”). Ars Technica, which extensively covers SpaceX, also interpreted Musk’s tweet as a positive outcome, saying: “According to Musk, the third burn went better than anticipated. ”

    1. Nathan: We’ve decided to leave “overshoot” as is. It does suggest a mistake, but not an egregious one, which seems to be the case here. It’s natural for SpaceX/Musk to attach positive language to any outcome concerning their project. But the scientific community does seem to overwhelmingly view the “overshoot” as a mistake or, at best, a miscalculation. By no means the only source to say so, this Popular Science story—with the headline “SpaceX’s Falcon Heavy launch was (mostly) a success” and a line about the Tesla orbit as “ever-so-slightly off”—offers a fair summation of what seems to be the prevailing reaction:

      1. I certainly agree that independent experts are a better source for neutral interpretation of these events than SpaceX or Musk. If you have links to expert opinions readily available, I would love to see them. Perhaps they should even be linked in the article! Traceability of claims is at the core of WikiTribune reporting, after all, although I understand that this particular claim is probably not high priority.

        Unfortunately, the popular science article you linked to does not quote any experts on this matter and is in fact incorrect about the intended destination of the car. It states that the Tesla roadster was “meant to enter orbit around Mars”. If this were true, then it would follow that SpaceX did indeed make a mistake. However, the intent all along was clearly to orbit around the sun, not Mars. SpaceX explain in their webcast prior to launch that the roadster is intended for a “heliocentric orbit”, whose outermost distance “will intersect the path that Mars takes”. Here is a link to that segment

        This leaves me personally still uncertain whether this overshoot was really a negative outcome (e.g. miscalculation or failure of second stage to throttle down) or positive outcome (test exceeded design specifications). But if you are confident in your interpretation, based on expert opinions (hopefully not just quotes from other journalists), then I don’t see any reason to push further. And I want to re-emphasize that I found your article to be good and informative overall. I certainly don’t have hard evidence to support a positive interpretation – just less confidence than you seem to have about the negative interpretation on this one (minor) point.

        1. This was never a real mission to Mars.

          They were only ever putting a dummy payload in to orbit around the Sun.

          Had it been a proper spacecraft then surely it would have had some propulsion system so that its orbit could be corrected to some extent.

          It’s also possible that they chose not to reprogram things relating to the car’s trajectory, after delaying the launch time.

          1. Good point. Precise orbit injection is not the job of the second stage. And the Roadster’s propulsion system is not very effective in space 😉

            So have we reached a consensus on this “talk” page that neutral language is more appropriate when discussing the fact that the payload will exceed Mars orbit at its farthest distance?

            I have certainly not yet seen any quotes from experts stating that the final orbit represents anything other than a success.

      2. ‘Overshoot’ may not sound too bad but in a real mission it would likely be really bad, implying missing the planet entirely and a total loss of cargo and/or astronauts.

        Based on the apparent goals of the launch – a message to potential customers of “Look how far we can throw a cargo into deep space.” rather than “We can send something to Mars.” – the ‘burn to empty’ hypothesis seems much more plausible. The article below in The Verge is the most technical I’ve read and does state that potential customers would likely be pleased seeing the Tesla getting thrown even further out into the system than they’d been told to expect. That’s the incentive for Spacex to use a burn-to-empty approach.
        The Verge too use the word ‘overshot’. However, with no hard evidence either way – that it was on one hand a mistake or on the other hand ‘better than expected performance’ – it may be better to use a neutral phrase like “Tesla Roadster will go further out into the system than original estimates indicated.”

        Does the wording really matter? Probably not to many. Spacex potential customers will clarify what happened and the general public won’t read much into it. But it would stop me (and a couple of others) sighing gently.

        Keep up the good work. Liked the article. None of the sensationalist or baseless or plain wrong journalism so prevalent elsewhere! We so need an honest and informed alternative to mainstream media.

      3. Just for full transparency, I found a link to where I got the idea that SpaceX planned to “burn until empty”:

        This again is not conclusive. It is a YouTube video by an enthusiast with a degree in astronomy, but he does not appear to currently work in astronomy. He does not state where his information comes from, but he states that this was a “burn to depletion” (sorry that in my original post I misremembered the technical term in he used), and he explains the term. He also does not explicitly state whether this is a positive or negative result.

      4. One more update. A Popular Mechanics article confirms the “burn to depletion”, quoting text taken directly from NASA JPL’s HORIZON tool. Link to PM article:

        But there’s a new twist. This JPL tool uses the SpaceX second stage’s own telemetry data and calculates a lower maximum distance than Elon’s tweet. This updated data suggest that “Starman” will only slightly exceed Mars’ orbit, and not reach the asteroid belt. See this updated diagram:

        Apparently, though, these predictions do not quite match ground-based observations, possibly due to venting of gases after the final burn, according to astronomer Jonathan McDowell:

        So we won’t know the final orbit for a little longer.

  3. Could mention that the central booster failed to land correctly on the barge.

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