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I don't agree the problems are comparable at all. The original Merlin engines were modern iterations of proven technology and vertical landing rockets were alr

I don't agree the problems are comparable at all. The original Merlin engines were modern iterations of proven technology and vertical landing rockets were already proven technology dating back many decades to the DC-X [1] and Apollo lunar lander. What SpaceX did was cut all the bullshit out of the space launch industry that had grown incredibly lazy due to lack of competitors and revolving doors with the government, and then modernize everything with iterative development. In comparison, commercially viable fusion has never been shown to work in the real world at all. The Raptor engine, however, really is a massive achievement and is somewhat comparable to developing fusion power. But if SpaceX had started with it, they probably would have failed due to how much time, money, and expertise it took to get working. [1] https://en.wikipedia.org/wiki/McDonnell_Douglas_DC-X https://en.wikipedia.org/wiki/McDonnell_Douglas_DC-X

vladTheInhaler 6y ago
I don't think that landing on the moon with lunar gravity and no atmosphere is at all comparable to surviving hypersonic reentry speeds and landing on such a tiny target. And reading the Wikipedia article, it doesn't sound like the DC-X ever demonstrated a landing from orbit, which is most of the challenge.
- everyone 6y ago
  Space X have never landed any rockets from orbit. Only their 1st stage has landed, which mainly goes up, its nowhere near orbital velocity.
  - vladTheInhaler 6y ago
    That's fair. Perhaps I should have said "from a trajectory that could plausibly lead it to orbit."
fastball 6y ago
Ok, so then someone should start a company that iterates on fission (proven tech like Merlin) and gets the cost of that way down and safety way up, then uses that momentum to work on fusion, which (like the Raptor engine) is a whole 'nother ball game, but you can still use some of the expertise from fission for fusion. The analogy holds!
- ubercore 6y ago
  I think fission to fusion is more like steam engine to jet engine. Fission can happen by _accident_ if you have the right materials at energy levels of just dropping something on something else [0]. Starting fusion isn't easy, but as I understand it, that's not even the hard part. Containment is the big deal, because of the energy needed. [0] https://en.wikipedia.org/wiki/Demon_core https://en.wikipedia.org/wiki/Demon_core
  - fastball 6y ago
    Isn't the Sun fusion happening by accident?
    - JoshuaDavid 6y ago
      Sure, and solar power is cheap fusion energy. Getting fusion energy without gravitational confinement is the tricky bit.
    - semi-extrinsic 6y ago
      Yeah, but the Sun only works because of its unfathomably massive size, compared to anything we can do on Earth. If you take 800 cubic meters of plasma from the core of the Sun, about the same volume as ITER, it only produces 216 kW - comparable to the engine in your car. And in that volume, you will have an average rate of 1500 hydrogen fusion reactions per second. Compared to ITER, this is something like twelve orders of magnitude slower. That is why ITER needs to go to much higher temperatures than the sun.
      - pfdietz 6y ago
        You have made an error somewhere. 1500 fusion reactions per second is maybe 10^10 eV per second, which would be around a nanowatt.
        semi-extrinsic 6y ago
        Yeah, you are right there is a mistake. I made a typo in Avogadro's number. Sorry about that! The power density is correct, but the number of reactions is too low by a factor of 10^10...
avmich 6y ago
> The Raptor engine, however, really is a massive achievement and is somewhat comparable to developing fusion power. Disagree, the theory of full-flow gas generators, and test bench results, were known for many years. At the same time with fusion we only have experience with uncontrolled one (bombs), or theory of how stars operate (and we can't reproduce that mechanism, not enough gravity). There is a lot more science to discover in fusion than in Raptors.
marvin 6y ago
Go back five years, to December 2015, and you’d find most people on Hacker News deride SpaceX’s landing attemps as impossible at worst or economically infeasible at best, three weeks before they first succeeded. Hopefully you (like me) were one of the ones cheering them on, but achievements that seem obvious in reterospect usually have had notoriously shaky statements about how obvious they were. Obviously the proponents are vindicated today, but it becomes a dodgy game of definitions when talking about how everyone who really had any insight knew that it was inevitable.
- ClumsyPilot 6y ago
  Well the opinions on Hackernews are only a little better than those on DailyMail when it comes to sibjects outside IT industry.
- pfdietz 6y ago
  Here's an interesting news story about Airbus Defense and Space (formerly Astrium)'s reaction to SpaceX, in January 2014: https://spacenews.com/38891a-hat-tip-to-spacex-as-rebranded-airbus-defence-and-space-takes-flight/#:~:text=A%20Hat%20Tip%20to%20SpaceX%20as%20Rebranded%20Airbus,an%20Airbus%20official%20said.%20%22What%20did%20SpaceX%20do%3F https://spacenews.com/38891a-hat-tip-to-spacex-as-rebranded-... What's fascinating about this is how NO ONE was talking about them getting the first stage to be reusable. Musk's plan looks like it exploited this blind spot. Reusing the first stage was so obviously impossible that even with the evidence of nine first stage engines staring them in the face, they thought this was just to minimize development cost. It was only when the legs went on that the penny dropped. And now, no one else will be able to repeat the free R&D flights that SpaceX got by trying to recover first stages off expendable launches sold at expendable launcher prices.
  - marvin 6y ago
    Thanks for digging up the concrete data backing up my claim. I was certain that I correctly remembered every observer that counted being blindsided by SpaceX’s success, in spite of their announcing their progress and stating their intentions time and time again. One really has to be meticulous to stay honest when looking at things in reterospect. And, by extension, when looking at lofty-sounding predictions about the future.

vladTheInhaler 6y ago

I don't think that landing on the moon with lunar gravity and no atmosphere is at all comparable to surviving hypersonic reentry speeds and landing on such a tiny target. And reading the Wikipedia article, it doesn't sound like the DC-X ever demonstrated a landing from orbit, which is most of the challenge.

everyone 6y ago
Space X have never landed any rockets from orbit. Only their 1st stage has landed, which mainly goes up, its nowhere near orbital velocity.
- vladTheInhaler 6y ago
  That's fair. Perhaps I should have said "from a trajectory that could plausibly lead it to orbit."

fastball 6y ago

Ok, so then someone should start a company that iterates on fission (proven tech like Merlin) and gets the cost of that way down and safety way up, then uses that momentum to work on fusion, which (like the Raptor engine) is a whole 'nother ball game, but you can still use some of the expertise from fission for fusion. The analogy holds!

ubercore 6y ago
I think fission to fusion is more like steam engine to jet engine. Fission can happen by _accident_ if you have the right materials at energy levels of just dropping something on something else [0]. Starting fusion isn't easy, but as I understand it, that's not even the hard part. Containment is the big deal, because of the energy needed. [0] https://en.wikipedia.org/wiki/Demon_core https://en.wikipedia.org/wiki/Demon_core
- fastball 6y ago
  Isn't the Sun fusion happening by accident?
  - JoshuaDavid 6y ago
    Sure, and solar power is cheap fusion energy. Getting fusion energy without gravitational confinement is the tricky bit.
  - semi-extrinsic 6y ago
    Yeah, but the Sun only works because of its unfathomably massive size, compared to anything we can do on Earth. If you take 800 cubic meters of plasma from the core of the Sun, about the same volume as ITER, it only produces 216 kW - comparable to the engine in your car. And in that volume, you will have an average rate of 1500 hydrogen fusion reactions per second. Compared to ITER, this is something like twelve orders of magnitude slower. That is why ITER needs to go to much higher temperatures than the sun.
    - pfdietz 6y ago
      You have made an error somewhere. 1500 fusion reactions per second is maybe 10^10 eV per second, which would be around a nanowatt.
      - semi-extrinsic 6y ago
        Yeah, you are right there is a mistake. I made a typo in Avogadro's number. Sorry about that! The power density is correct, but the number of reactions is too low by a factor of 10^10...

avmich 6y ago

> The Raptor engine, however, really is a massive achievement and is somewhat comparable to developing fusion power. Disagree, the theory of full-flow gas generators, and test bench results, were known for many years. At the same time with fusion we only have experience with uncontrolled one (bombs), or theory of how stars operate (and we can't reproduce that mechanism, not enough gravity). There is a lot more science to discover in fusion than in Raptors.

marvin 6y ago

Go back five years, to December 2015, and you’d find most people on Hacker News deride SpaceX’s landing attemps as impossible at worst or economically infeasible at best, three weeks before they first succeeded. Hopefully you (like me) were one of the ones cheering them on, but achievements that seem obvious in reterospect usually have had notoriously shaky statements about how obvious they were. Obviously the proponents are vindicated today, but it becomes a dodgy game of definitions when talking about how everyone who really had any insight knew that it was inevitable.

ClumsyPilot 6y ago
Well the opinions on Hackernews are only a little better than those on DailyMail when it comes to sibjects outside IT industry.
pfdietz 6y ago
Here's an interesting news story about Airbus Defense and Space (formerly Astrium)'s reaction to SpaceX, in January 2014: https://spacenews.com/38891a-hat-tip-to-spacex-as-rebranded-airbus-defence-and-space-takes-flight/#:~:text=A%20Hat%20Tip%20to%20SpaceX%20as%20Rebranded%20Airbus,an%20Airbus%20official%20said.%20%22What%20did%20SpaceX%20do%3F https://spacenews.com/38891a-hat-tip-to-spacex-as-rebranded-... What's fascinating about this is how NO ONE was talking about them getting the first stage to be reusable. Musk's plan looks like it exploited this blind spot. Reusing the first stage was so obviously impossible that even with the evidence of nine first stage engines staring them in the face, they thought this was just to minimize development cost. It was only when the legs went on that the penny dropped. And now, no one else will be able to repeat the free R&D flights that SpaceX got by trying to recover first stages off expendable launches sold at expendable launcher prices.
- marvin 6y ago
  Thanks for digging up the concrete data backing up my claim. I was certain that I correctly remembered every observer that counted being blindsided by SpaceX’s success, in spite of their announcing their progress and stating their intentions time and time again. One really has to be meticulous to stay honest when looking at things in reterospect. And, by extension, when looking at lofty-sounding predictions about the future.