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So knowing nothing about this subject, why do they pursue landing rockets, or at least landing them vertically? It seems like the hardest possible way to handle

So knowing nothing about this subject, why do they pursue landing rockets, or at least landing them vertically? It seems like the hardest possible way to handle this problem, as opposed to for example what the shuttles did. Can anyone explain the reasoning behind this?

DanielStraight 10y ago
Why land? Fuel makes up a very small percent of the launch cost of a rocket. Landing also allows a much better experience for cargo and crew return, and it makes it possible to bring equipment to other planets or moons. Why vertical? Vertical landing is much more flexible. You can land on a barge at sea. You can land on the launchpad itself. You can land on a planet or moon with no atmosphere.
- nicolapcweek94 10y ago
  > You can land on a planet or moon with no atmosphere. IE: Mars, the ultimate SpaceX goal, which has just enough atmosphere to be annoying but not nearly enough to make parachutes work, so they had to find another way to land a big enough payload to transport 100 tons of stuff there
  - andars 10y ago
    The first stage will not land on Mars.
    - nicolapcweek94 10y ago
      No it won't, but they're definitely gonna reuse the tech they're developing to land the S1 on Earth to land the MCT on Mars And to land the BFR S1 on Earth, which I'd guess would be a bit too much for parachutes even with Earth's relatively thick atmosphere, if what people have been saying on Reddit is right September 21st can't come soon enough!
    - JshWright 10y ago
      No, but the cool thing is, SpaceX is using their first stage landings to do research that will advance their goals on Mars. In order to land large payloads on Mars, SpaceX is going to have to do something that, up until recently, has never been done before. They're going to have to fire a rocket engine 'backwards' in an atmosphere (albeit a thin one) while travelling at supersonic speeds. This will be necessary in order to slow down enough to actually land (parachutes don't buy you much on Mars). This 'supersonic retropropulsion' is something that has been modeled a lot, but is really hard to actually test. You would need to get a rocket up to supersonic speeds, in the thin upper stages of Earth's atmosphere (where the conditions are close to that of Mars) and have it fire its engines backwards. As luck would have it, that's exactly what the Falcon 9 first stage does during its reentry burn. The data they are collecting now will be invaluable in designing their Mars bound spacecraft. NASA is also very interested in this data: https://www.nasa.gov/press/2014/october/new-commercial-rocket-descent-data-may-help-nasa-with-future-mars-landings/ https://www.nasa.gov/press/2014/october/new-commercial-rocke...
  - Retric 10y ago
    All methods of landing on Mars require an aeroshell and parachute sequence, but after that there are three choices https://en.m.wikipedia.org/wiki/Mars_landing https://en.m.wikipedia.org/wiki/Mars_landing The advantage to powered landings is they work well for delicate stuff like people. Or in space X's case they are landing a really light shell and have a really powerful engine already attached.
    - nicolapcweek94 10y ago
      Well, they're landing a really light shell with a really powerful engine for now, on Earth. Mars is gonna be a different story, considering the Red Dragon mission in 2018 (with already existing infrastructure, since the Red Dragon will basically be a Dragon 2 capsule and the S1 for the mission will be a Falcon Heavy) is gonna have the heaviest payload ever landed on mars with a semi-empty Dragon 2, and all the missions after that will probably try to land at least one MCT, which would be heavier of a Dragon 2 by itself, with some cargo... Luckily the MCT will have an even more powerful engine, and Mars's lighter gravity will probably help!
    - phire 10y ago
      I feel like there is a [Citation Needed] for that Wikipedia quote. All existing landers used an aeroshell and parachute sequence, but that doesn't mean it's impossible to land with just Rockets. The aeroshell/parachute method is used because it allows landers to come straight in from a Hoffman transfer orbit, bleed off all that extra speed and land with the least amount of fuel required. But it's way to risky for a manned lander, as the landing date (and location) are locked in months ahead of time with no option for an abort or delay. A manned lander is likely to aerobreak into a stabke Mars parking orbit first. Allowing the crew can check the lander, check the weather at the landing site and detach from a reusable transfer module. From low Mars orbit, they are going much slower and need to disperse much less energy. You could just throw Rockets and fuel at the problem. Or wings might be far more attractive than a parachute for slowing down in the upper atmosphere (though, any wings would have to be massive to actually glide all the way down to the lower atmosphere or land)
      - 10y ago
ragebol 10y ago
The space shuttle was not retired because it was too easy to keep them in flight/orbit. The space shuttle as a whole, with the boosters, external tank, wings, wheeled landing gear was also very complex and costly. More complex than a SpaceX Falcon 9, dare I say.
Symmetry 10y ago
All the extra weight from the Shuttle's aerodynamic surfaces would really cut into SpaceX's cargo capability too much. And remember that the part that landed was only a small fraction of whole launch system's bulk. SpaceX is hoping to eventually get a quick turnaround which means not throwing away lots of parts. And in the short term they can make incremental progress because what they're using to land isn't much more than what they needed to get to space in the first place.
timdiggerm 10y ago
The experience of the Shuttle program demonstrated that taking off like a rocket and landing like a plane has a lot of problems that make it not as great as you might think. The wings, heat shield, etc are all pretty heavy - notice that the shuttle required two whole extra rockets and a disposable fuel tank to make it to orbit - and the heat shield required for landing like a plane turned out to be a huge problem (see: The Columbia Disaster). Plus, it turns out that landing a rocket vertically is now possible. I'm not clear on if it's now possible thanks to advances in technology (particularly in automation) or if it's just that no one had tried it until now.
- aninhumer 10y ago
  Note that the Space Shuttle only needs a heat shield because it's returning from orbital velocity. The Falcon 9 first stage is suborbital.
  - timdiggerm 10y ago
    Oh yeah, that's a very good point.
  - kirrent 10y ago
    Even at the far slower speed the first stage would still be damaged from re-entry. That's why they do a re-entry burn to slow the stage down before the atmosphere gets too dense. There's apparently also some interesting physics on the engine firing dissipating the bow shock which helps keep temperatures down.
mattferderer 10y ago
I recommend checking out episode 1313 of the podcast .Net Rocks. They do an awesome job explaining this subject even if you have no background knowledge on it.
aninhumer 10y ago
Landing vertically is very similar to taking off vertically in terms of the physical requirements of the vehicle. If you want to land like a plane, you need a much more complex design, which is almost certainly worse at taking off. So as long as you can work out how to control it reliably, vertical landing is a lot more efficient than horizontal landing.
phkahler 10y ago
> So knowing nothing about this subject, why do they pursue landing rockets, or at least landing them vertically? It seems like the hardest possible way to handle this problem, as opposed to for example what the shuttles did. Can anyone explain the reasoning behind this? It's actually the least complex way to do it. You've already got the engines to slow descent and steer the vehicle. At the highest concept level, all you need is to add more fuel and have very high-performance control system for guidance. Oh, and bolt on some landing legs, and some grid fins. That's not to say it's easy, but the added hardware is way less complex than adding wings, using a runway, etc... But if you watch their landings now they make it look easy and to suggest adding a bunch of other hardware complexity to get the rocket back seems silly in hindsight. The challenge is to take someones simplistic idea "just have the rocket land itself" and look at it objectively even though nobody does it that way. My own preconceived ideas told me it would require way too much fuel to be practical. Turns out that's wrong. I also thought things would get too hot on re-entry. Turns out that's wrong too. But from a hardware complexity standpoint, it does seem kind of obvious doesn't it? I mean Bugs Bunny landed a rocket on mars right? Why NOT do it like that? http://www.cartoonsonnet.com/bugs-bunny-mad-as-a-mars-hare.html http://www.cartoonsonnet.com/bugs-bunny-mad-as-a-mars-hare.h...

DanielStraight 10y ago

Why land? Fuel makes up a very small percent of the launch cost of a rocket. Landing also allows a much better experience for cargo and crew return, and it makes it possible to bring equipment to other planets or moons. Why vertical? Vertical landing is much more flexible. You can land on a barge at sea. You can land on the launchpad itself. You can land on a planet or moon with no atmosphere.

nicolapcweek94 10y ago
> You can land on a planet or moon with no atmosphere. IE: Mars, the ultimate SpaceX goal, which has just enough atmosphere to be annoying but not nearly enough to make parachutes work, so they had to find another way to land a big enough payload to transport 100 tons of stuff there
- andars 10y ago
  The first stage will not land on Mars.
  - nicolapcweek94 10y ago
    No it won't, but they're definitely gonna reuse the tech they're developing to land the S1 on Earth to land the MCT on Mars And to land the BFR S1 on Earth, which I'd guess would be a bit too much for parachutes even with Earth's relatively thick atmosphere, if what people have been saying on Reddit is right September 21st can't come soon enough!
  - JshWright 10y ago
    No, but the cool thing is, SpaceX is using their first stage landings to do research that will advance their goals on Mars. In order to land large payloads on Mars, SpaceX is going to have to do something that, up until recently, has never been done before. They're going to have to fire a rocket engine 'backwards' in an atmosphere (albeit a thin one) while travelling at supersonic speeds. This will be necessary in order to slow down enough to actually land (parachutes don't buy you much on Mars). This 'supersonic retropropulsion' is something that has been modeled a lot, but is really hard to actually test. You would need to get a rocket up to supersonic speeds, in the thin upper stages of Earth's atmosphere (where the conditions are close to that of Mars) and have it fire its engines backwards. As luck would have it, that's exactly what the Falcon 9 first stage does during its reentry burn. The data they are collecting now will be invaluable in designing their Mars bound spacecraft. NASA is also very interested in this data: https://www.nasa.gov/press/2014/october/new-commercial-rocket-descent-data-may-help-nasa-with-future-mars-landings/ https://www.nasa.gov/press/2014/october/new-commercial-rocke...
- Retric 10y ago
  All methods of landing on Mars require an aeroshell and parachute sequence, but after that there are three choices https://en.m.wikipedia.org/wiki/Mars_landing https://en.m.wikipedia.org/wiki/Mars_landing The advantage to powered landings is they work well for delicate stuff like people. Or in space X's case they are landing a really light shell and have a really powerful engine already attached.
  - nicolapcweek94 10y ago
    Well, they're landing a really light shell with a really powerful engine for now, on Earth. Mars is gonna be a different story, considering the Red Dragon mission in 2018 (with already existing infrastructure, since the Red Dragon will basically be a Dragon 2 capsule and the S1 for the mission will be a Falcon Heavy) is gonna have the heaviest payload ever landed on mars with a semi-empty Dragon 2, and all the missions after that will probably try to land at least one MCT, which would be heavier of a Dragon 2 by itself, with some cargo... Luckily the MCT will have an even more powerful engine, and Mars's lighter gravity will probably help!
  - phire 10y ago
    I feel like there is a [Citation Needed] for that Wikipedia quote. All existing landers used an aeroshell and parachute sequence, but that doesn't mean it's impossible to land with just Rockets. The aeroshell/parachute method is used because it allows landers to come straight in from a Hoffman transfer orbit, bleed off all that extra speed and land with the least amount of fuel required. But it's way to risky for a manned lander, as the landing date (and location) are locked in months ahead of time with no option for an abort or delay. A manned lander is likely to aerobreak into a stabke Mars parking orbit first. Allowing the crew can check the lander, check the weather at the landing site and detach from a reusable transfer module. From low Mars orbit, they are going much slower and need to disperse much less energy. You could just throw Rockets and fuel at the problem. Or wings might be far more attractive than a parachute for slowing down in the upper atmosphere (though, any wings would have to be massive to actually glide all the way down to the lower atmosphere or land)
    - 10y ago

ragebol 10y ago

The space shuttle was not retired because it was too easy to keep them in flight/orbit. The space shuttle as a whole, with the boosters, external tank, wings, wheeled landing gear was also very complex and costly. More complex than a SpaceX Falcon 9, dare I say.

Symmetry 10y ago

All the extra weight from the Shuttle's aerodynamic surfaces would really cut into SpaceX's cargo capability too much. And remember that the part that landed was only a small fraction of whole launch system's bulk. SpaceX is hoping to eventually get a quick turnaround which means not throwing away lots of parts. And in the short term they can make incremental progress because what they're using to land isn't much more than what they needed to get to space in the first place.

timdiggerm 10y ago

The experience of the Shuttle program demonstrated that taking off like a rocket and landing like a plane has a lot of problems that make it not as great as you might think. The wings, heat shield, etc are all pretty heavy - notice that the shuttle required two whole extra rockets and a disposable fuel tank to make it to orbit - and the heat shield required for landing like a plane turned out to be a huge problem (see: The Columbia Disaster). Plus, it turns out that landing a rocket vertically is now possible. I'm not clear on if it's now possible thanks to advances in technology (particularly in automation) or if it's just that no one had tried it until now.

aninhumer 10y ago
Note that the Space Shuttle only needs a heat shield because it's returning from orbital velocity. The Falcon 9 first stage is suborbital.
- timdiggerm 10y ago
  Oh yeah, that's a very good point.
- kirrent 10y ago
  Even at the far slower speed the first stage would still be damaged from re-entry. That's why they do a re-entry burn to slow the stage down before the atmosphere gets too dense. There's apparently also some interesting physics on the engine firing dissipating the bow shock which helps keep temperatures down.

mattferderer 10y ago

I recommend checking out episode 1313 of the podcast .Net Rocks. They do an awesome job explaining this subject even if you have no background knowledge on it.

aninhumer 10y ago

Landing vertically is very similar to taking off vertically in terms of the physical requirements of the vehicle. If you want to land like a plane, you need a much more complex design, which is almost certainly worse at taking off. So as long as you can work out how to control it reliably, vertical landing is a lot more efficient than horizontal landing.

phkahler 10y ago

> So knowing nothing about this subject, why do they pursue landing rockets, or at least landing them vertically? It seems like the hardest possible way to handle this problem, as opposed to for example what the shuttles did. Can anyone explain the reasoning behind this? It's actually the least complex way to do it. You've already got the engines to slow descent and steer the vehicle. At the highest concept level, all you need is to add more fuel and have very high-performance control system for guidance. Oh, and bolt on some landing legs, and some grid fins. That's not to say it's easy, but the added hardware is way less complex than adding wings, using a runway, etc... But if you watch their landings now they make it look easy and to suggest adding a bunch of other hardware complexity to get the rocket back seems silly in hindsight. The challenge is to take someones simplistic idea "just have the rocket land itself" and look at it objectively even though nobody does it that way. My own preconceived ideas told me it would require way too much fuel to be practical. Turns out that's wrong. I also thought things would get too hot on re-entry. Turns out that's wrong too. But from a hardware complexity standpoint, it does seem kind of obvious doesn't it? I mean Bugs Bunny landed a rocket on mars right? Why NOT do it like that? http://www.cartoonsonnet.com/bugs-bunny-mad-as-a-mars-hare.html http://www.cartoonsonnet.com/bugs-bunny-mad-as-a-mars-hare.h...