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I think Dragon 2 is a propulsive landing all the way, with parachutes used only in case of emergency. /r/spacex would be a good place to ask this (and the moon

I think Dragon 2 is a propulsive landing all the way, with parachutes used only in case of emergency. /r/spacex would be a good place to ask this (and the moon landing question), lots of people are quite knowledgeable and like running numbers like this.

jordanthoms 11y ago
Yep, Dragon 2 is capable of propulsive landing with no parachutes on earth, although to begin with it'll use parachutes and land in the water (perhaps using the engines to soften the landing). Interestingly, Dragon 2 does have enough fuel to land on Mars, with clever aerobraking. NASA has done some feasibility studies on using a Dragon to land on Mars with a sample return vehicle inside it.
mikeash 11y ago
Dragon 2 is going to start out doing parachute landings with no propulsion at all. Once the system is sufficiently proven, they'll switch over to propulsive landings, where the parachutes are just an emergency backup in case the engines don't light or something.
- ansible 11y ago
  They also need the parachutes because if there is an emergency during launch, the thrusters will be used to separate the capsule from the launch vehicle. They demonstrated this with their pad abort test: https://www.youtube.com/watch?v=1_FXVjf46T8 https://www.youtube.com/watch?v=1_FXVjf46T8 Perhaps later this year we will also see an in-flight abort test, which will be very exciting.
- sandworm101 11y ago
  Won't happen. Nasa will never do a purely propulsive landing of such a craft. Parachutes cannot act as backup to a rocket-powered landing. Chutes need speed+altitude to deploy. If the rockets fail 25 meters above the ground, chutes won't save anything. If the craft has chutes+people on board, they will be deployed long before touchdown. Better out than in. The only fully propulsive landing option, with humans on board, would be to have a second set of engines ready to perform what in an airplane would be called a zero-zero ejection maneuver[1]. This would see the craft reverse course, ascending rapidly to a trajectory where the chutes have time/energy enough to properly deploy. It would basically be a launch escape system. To keep that, and the chutes, and the descent engines ... just use the chutes. It isn't saving much money not deploying them as they will probably require repacking for inspection either way. [1]A zero-zero ejection seat is one that can save a pilot from a craft parked on the runway, at zero-speed and zero altitude. Older seats required altitude and/or speed. But the dragon would be descending, with a negative alt/speed, so I guess this would be a sub-zero-zero ejection. A descent escape maneuver?
  - tempestn 11y ago
    You make some useful points about the challenges. However, NASA will never do a purely propulsive landing of such a craft? Is it really inconceivable that over time it could become, and be demonstrated to be, at least equally safe to using parachutes?
    - sandworm101 11y ago
      Never isn't from a policy but a physics standpoint. If the chutes are already there, then it makes sense to use them. They are lighter/cheaper than hauling a full backup rocket system. From what I've seen, it looks like SpaceX plans on using the rockets to cushion a landing already under chutes, like the russians do today. That allows for much smaller chutes and faster landing. If the rockets fail then the landing with be rough but still survivable, with the re-usability of the craft being written off. The propulsive landing of booster stages makes sense only because you already have giant engine/fuel reserves, which aren't going to orbit. And since there are no humans around you don't need any sort of abort option. Also, if you are going to have a potentially rough landing, would you rather do so sitting 6" from a box containing a parachute, or 6" from a tank of rocket fuel?
      - tempestn 11y ago
        > Also, if you are going to have a potentially rough landing, would you rather do so sitting 6" from a box containing a parachute, or 6" from a tank of rocket fuel? The former, of course. I agree that a propulsive landing wouldn't be likely any time in the near future. But if it could eventually be shown to be safe (and therefore the quote above doesn't apply), I don't necessarily agree that it would be more expensive. You wouldn't need large engines or a lot of fuel, as the capsule wouldn't be very heavy. Yes, it would definitely still be more expensive than parachutes in terms of equipment and weight. However, it would mean you could land right back at your facility, rather than splashing down in the ocean and dealing with retrieval. When we're looking into the future of reusable, commodity space travel, that would be a significant advantage.
        11y ago
dogma1138 11y ago
IIRC NASA missions (at least initially) will use parachute landing while other missions will use propulsive landing. The propulsive landing engines serve in case of mission abort so they aren't wasted in any case, but as it's looking now NASA will not be trusting them for landings.

jordanthoms 11y ago

Yep, Dragon 2 is capable of propulsive landing with no parachutes on earth, although to begin with it'll use parachutes and land in the water (perhaps using the engines to soften the landing). Interestingly, Dragon 2 does have enough fuel to land on Mars, with clever aerobraking. NASA has done some feasibility studies on using a Dragon to land on Mars with a sample return vehicle inside it.

mikeash 11y ago

Dragon 2 is going to start out doing parachute landings with no propulsion at all. Once the system is sufficiently proven, they'll switch over to propulsive landings, where the parachutes are just an emergency backup in case the engines don't light or something.

ansible 11y ago
They also need the parachutes because if there is an emergency during launch, the thrusters will be used to separate the capsule from the launch vehicle. They demonstrated this with their pad abort test: https://www.youtube.com/watch?v=1_FXVjf46T8 https://www.youtube.com/watch?v=1_FXVjf46T8 Perhaps later this year we will also see an in-flight abort test, which will be very exciting.
sandworm101 11y ago
Won't happen. Nasa will never do a purely propulsive landing of such a craft. Parachutes cannot act as backup to a rocket-powered landing. Chutes need speed+altitude to deploy. If the rockets fail 25 meters above the ground, chutes won't save anything. If the craft has chutes+people on board, they will be deployed long before touchdown. Better out than in. The only fully propulsive landing option, with humans on board, would be to have a second set of engines ready to perform what in an airplane would be called a zero-zero ejection maneuver[1]. This would see the craft reverse course, ascending rapidly to a trajectory where the chutes have time/energy enough to properly deploy. It would basically be a launch escape system. To keep that, and the chutes, and the descent engines ... just use the chutes. It isn't saving much money not deploying them as they will probably require repacking for inspection either way. [1]A zero-zero ejection seat is one that can save a pilot from a craft parked on the runway, at zero-speed and zero altitude. Older seats required altitude and/or speed. But the dragon would be descending, with a negative alt/speed, so I guess this would be a sub-zero-zero ejection. A descent escape maneuver?
- tempestn 11y ago
  You make some useful points about the challenges. However, NASA will never do a purely propulsive landing of such a craft? Is it really inconceivable that over time it could become, and be demonstrated to be, at least equally safe to using parachutes?
  - sandworm101 11y ago
    Never isn't from a policy but a physics standpoint. If the chutes are already there, then it makes sense to use them. They are lighter/cheaper than hauling a full backup rocket system. From what I've seen, it looks like SpaceX plans on using the rockets to cushion a landing already under chutes, like the russians do today. That allows for much smaller chutes and faster landing. If the rockets fail then the landing with be rough but still survivable, with the re-usability of the craft being written off. The propulsive landing of booster stages makes sense only because you already have giant engine/fuel reserves, which aren't going to orbit. And since there are no humans around you don't need any sort of abort option. Also, if you are going to have a potentially rough landing, would you rather do so sitting 6" from a box containing a parachute, or 6" from a tank of rocket fuel?
    - tempestn 11y ago
      > Also, if you are going to have a potentially rough landing, would you rather do so sitting 6" from a box containing a parachute, or 6" from a tank of rocket fuel? The former, of course. I agree that a propulsive landing wouldn't be likely any time in the near future. But if it could eventually be shown to be safe (and therefore the quote above doesn't apply), I don't necessarily agree that it would be more expensive. You wouldn't need large engines or a lot of fuel, as the capsule wouldn't be very heavy. Yes, it would definitely still be more expensive than parachutes in terms of equipment and weight. However, it would mean you could land right back at your facility, rather than splashing down in the ocean and dealing with retrieval. When we're looking into the future of reusable, commodity space travel, that would be a significant advantage.
      - 11y ago

dogma1138 11y ago

IIRC NASA missions (at least initially) will use parachute landing while other missions will use propulsive landing. The propulsive landing engines serve in case of mission abort so they aren't wasted in any case, but as it's looking now NASA will not be trusting them for landings.