SpaceX And/Or Rocketry In General

archae86
archae86
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SpaceX has posted video of a

SpaceX has posted video of a propulsive hover test of the Dragon capsule. You can choose pretty high resolution if you like. The test happened in November, 2015, but the posting of the video is quite recent.

Not much happens, but that is the point--it hovers on rocket power. Unlike the Soyuz little bang that just reduces the landing impact some, Dragon is meant to be able to do a controlled landing using rocket thrust, so needs to throttle with real precision.

These thrusters are the propulsive component of the launch escape system, so this vehicle does not use simple dumb solids for that function.

robl
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RE: SpaceX has posted video

Quote:

SpaceX has posted video of a propulsive hover test of the Dragon capsule. You can choose pretty high resolution if you like. The test happened in November, 2015, but the posting of the video is quite recent.

Not much happens, but that is the point--it hovers on rocket power. Unlike the Soyuz little bang that just reduces the landing impact some, Dragon is meant to be able to do a controlled landing using rocket thrust, so needs to throttle with real precision.

These thrusters are the propulsive component of the launch escape system, so this vehicle does not use simple dumb solids for that function.

There was a test here a few month back when they launched a Dragon on a "short" rocket. Both parts launched and the the Dragon separated and moved at a rapid rate away from the 1st stage before deploying parachutes and splashing into the ocean. I thought this was its normal mode of operation. Are you implying that parachutes will not be utilized but rather a soft landing as implied in this video using thrusters? When the Dragon becomes an escape pod you have very little choice of where you are going to go/land. Most likely feet wet.

archae86
archae86
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RE: Both parts launched and

Quote:
Both parts launched and the the Dragon separated and moved at a rapid rate away from the 1st stage before deploying parachutes and splashing into the ocean. I thought this was its normal mode of operation. Are you implying that parachutes will not be utilized but rather a soft landing as implied in this video using thrusters? When the Dragon becomes an escape pod you have very little choice of where you are going to go/land. Most likely feet wet.

In escape system use, I doubt there would be enough fuel left to use the rockets again for landing. However escape system use is not the normal operating mode.

Yes it is the plan to use true soft landing on land in crewed operation.

archae86
archae86
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As clarification, I suspect

As clarification, I suspect the plan is to use parachute supplemented by rocket, not rockets alone, as I imagine a moderate parachute can bleed off more velocity than the same weight in propellant.

On the other hand, if they want really precise landing locations, maybe they'll make the parachute smaller than would otherwise be used.

In the case of Soyuz, I think the parachute is supposed to slow it enough for a landing in which the soft landing rockets fail to be survivable. 24 feet per second would not, however be comfortable. So they fire six retrorockets at altitude less than three feet, which if all goes well reduce the final impact speed to 3.1 mph. As that is 4.5 fps, it is a drastic improvement, but those who have experienced it liken it to a car crash. The video looks more like a small last-moment explosion than a rocket burn.

This Youtube video includes two views of an actual impact (landing) with two different camera angles in quick succession starting around time 0:40.

I suspect the car crash feeling comes as much from the very abrupt retrorocket burn as it does from the true ground impact.

AgentB
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RE: I suspect the car crash

Quote:
I suspect the car crash feeling comes as much from the very abrupt retrorocket burn as it does from the true ground impact.

Unofficial footage of Soyuz landing from inside you'll notice Samantha Christofetti getting quite a whiplash effect.

archae86
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AgentB, I may be suffering

AgentB, I may be suffering from confirmation bias, but I do think in that video you can see the jolt from the retro burn followed quite quickly by the actual ground impact jolt.

AgentB
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An Astronaut concurs.. You

An Astronaut concurs.. You see the flash through the window at well. I guess it probably rolls over on its side at the end.

robl
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RE: RE: Both parts

Quote:
Quote:
Both parts launched and the the Dragon separated and moved at a rapid rate away from the 1st stage before deploying parachutes and splashing into the ocean. I thought this was its normal mode of operation. Are you implying that parachutes will not be utilized but rather a soft landing as implied in this video using thrusters? When the Dragon becomes an escape pod you have very little choice of where you are going to go/land. Most likely feet wet.

In escape system use, I doubt there would be enough fuel left to use the rockets again for landing. However escape system use is not the normal operating mode.

Yes it is the plan to use true soft landing on land in crewed operation.

I was under the impression that the onboard thrusters were for escape only and that the capsule was going to parachute to a water recovery.

[EDIT] A land based recovery would make more sense and the thrusters would allow that.

archae86
archae86
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I've not found much on

I've not found much on detailed Dragon landing mode plans in looking around today, but this animation posted by SpaceX themselves in May 2014, appears to show no use of parachutes for a nominal mode landing at all (contrary to my guess a few posts earlier).

Where this animation stands between fever dream and serious representation of then-current eventual plans I don't know.

But those of us who grew up thinking it was perfectly natural for a landing manned spacecraft to have the undivided attentions of an aircraft carrier and various support craft might contemplate the potential savings of landing on land--with no salt spray corrosion concerns as an obstacle to re-use as a bonus.

AgentB
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It seems they will start with

It seems they will start with parachute first (Aug 2014 so a bit dated) - a bit of detail here dragon-v2

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