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.
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.
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
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!
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-rocke...
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.
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!
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)
Edit: Here, they start at well over 10,000mph heat shield drops that to ~1000mph, parashoot drops that to ~200mph. http://i.i.cbsi.com/cnwk.1d/i/tim//2010/08/12/2012MSLSkyCran...
PS: As to just burning fuel getting literally tons of wasted rocket fuel on mars is really really expensive.
PPS: At 0.6% ATM storms are only a viability problem. Only a tiny amount of ultra fine dust can get suspended.
> Parachute can bleed off 80+% of that speed for little additional weight unlike wings which would need to survive supersonic retry heating making parachutes a no brainier.
Sure, Parachutes make a lot of sense for a one way trip.
But Parachutes are a consumable, one which would be really hard to manufacture on Mars (compared to rocket fuel, which just requires water, carbon dioxide and electricity). Also the size of the parachute gets ridiculously large for larger spacecraft.
If you are planning to make a rocket which shuttles people or cargo (or fuel) between Mars' surface and low Mars orbit, then it makes a whole lot more sense to just manufacture the extra fuel on Mars rather than trying to manufacture parachutes on Mars or shipping extra parachutes to Mars.
As for wings, you don't really want to use them for the subsonic phase. I'm not really sure how viable the idea is, but you want to use them to prolong your trip through the upper atmosphere, where the atmosphere is thinner. This allows you to stretch out all that supersonic atmospheric heating over a much longer time period, at a much slower rate than what your heat shield can dissipate.
Retractable or reconfigurable wings might be needed so you can maximize lift in the upper atmosphere then minimise drag through the supersonic to subsonic transition.
I notice that Spacex have designed their ablative heat shield to which can withstand hundreds of reentries to Earth without any replacement or refurbishment. Still technically a consumable, but I really doubt anyone is happy with re-packing and re-using the same reentry parachutes hundreds of times.
And that's reentries to Earth, where the entry velocity is 17,000mph and the atmosphere is 100 times thicker. Such a heatsheild can probably withstand thousands of Mars reentries at just 7000mph before replacement.
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.h...
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.
So as long as you can work out how to control it reliably, vertical landing is a lot more efficient than horizontal landing.