This is great stuff! .I'm also not sure how the drop tests are going to use all of 300 gallons of fuel but the hop tests will only need 400 gallons, ISTM like that ascent burn should consume a lot of fuel, even if the descent burn doesn't need as much.Anyway, it's great to finally see some details about this program.
Reread it, it states UP TO before listing Height, fuel quantity, etc...
How could they have a controlled pinpoint landing back at the pad if they are using parachutes and if there is any sort of wind? I would think that this poses significant drift potential from 10,000 ft. They could drift quite a distance off of center. Once the Dracos fire, I think the potential for needing way more than 5 seconds is significant.
I'm intrigued with this integrated trunk as well. Theoretically they could have designed a new trunk that would accommodate legs and enough fuel to do a Moon or Mars decent / ascent. (ladder included)
Quote from: rcoppola on 05/21/2014 06:15 pmI'm intrigued with this integrated trunk as well. Theoretically they could have designed a new trunk that would accommodate legs and enough fuel to do a Moon or Mars decent / ascent. (ladder included)I would be careful to interpret too much into it, but it does sound interesting, indeed. Maybe the new Dragon will not lose the trunk anymore?Hmmm.Either way, I cant wait to see test hops of this! This must be really cool to watch!
Quote from: RocketGoBoom on 05/21/2014 06:02 pmHow could they have a controlled pinpoint landing back at the pad if they are using parachutes and if there is any sort of wind? I would think that this poses significant drift potential from 10,000 ft. They could drift quite a distance off of center. Once the Dracos fire, I think the potential for needing way more than 5 seconds is significant.I see propulsive assist landing to be similar to Soyuz. Land landing with parachutes, with engines smoothing the touchdown (but with the landing survivable even if they do not fire).Beats fishing out the crews and cargo from the ocean, even if you need a fairly large open area to aim for. Could totally see this happening in future orbital flights as an intermediate step towards propulsive-only landing.
Quote from: sublimemarsupial on 05/21/2014 05:01 pmQuote from: Lars_J on 05/21/2014 04:49 pmQuote from: JBF on 05/21/2014 04:42 pmQuote from: Jarnis on 05/21/2014 04:33 pmFreefall, 5 sec burn at the last moment, soft touchdown.Whoever will ultimately ride aboard that kind of flight profile (obviously not during these tests) is a brave man Can anyone model the G-Force curve on that? It sounds like a rough ride.If anyone can guess the terminal velocity of the capsule, it should be easy to calculate. If the G-load is evenly spread over 5 seconds, it might not be too bad.For a very first order estimate I get a terminal velocity of ~150 m/s given a total mass of 17,000 lbs (dry mass plus 3000 lbs of fuel) and a drag coefficient of 0.8.A 5 second burn to brake from 150 m/s would result in an average of ~3Gs of deceleration.
Quote from: Lars_J on 05/21/2014 04:49 pmQuote from: JBF on 05/21/2014 04:42 pmQuote from: Jarnis on 05/21/2014 04:33 pmFreefall, 5 sec burn at the last moment, soft touchdown.Whoever will ultimately ride aboard that kind of flight profile (obviously not during these tests) is a brave man Can anyone model the G-Force curve on that? It sounds like a rough ride.If anyone can guess the terminal velocity of the capsule, it should be easy to calculate. If the G-load is evenly spread over 5 seconds, it might not be too bad.For a very first order estimate I get a terminal velocity of ~150 m/s given a total mass of 17,000 lbs (dry mass plus 3000 lbs of fuel) and a drag coefficient of 0.8.
Quote from: JBF on 05/21/2014 04:42 pmQuote from: Jarnis on 05/21/2014 04:33 pmFreefall, 5 sec burn at the last moment, soft touchdown.Whoever will ultimately ride aboard that kind of flight profile (obviously not during these tests) is a brave man Can anyone model the G-Force curve on that? It sounds like a rough ride.If anyone can guess the terminal velocity of the capsule, it should be easy to calculate. If the G-load is evenly spread over 5 seconds, it might not be too bad.
Quote from: Jarnis on 05/21/2014 04:33 pmFreefall, 5 sec burn at the last moment, soft touchdown.Whoever will ultimately ride aboard that kind of flight profile (obviously not during these tests) is a brave man Can anyone model the G-Force curve on that? It sounds like a rough ride.
Freefall, 5 sec burn at the last moment, soft touchdown.Whoever will ultimately ride aboard that kind of flight profile (obviously not during these tests) is a brave man
Any concerns about the capsule being tilted ~30 degrees from vertical due to the parachute attach point being on the side? See picture(s) captured from the Drop test video. Firing off the Draco Engines on landing may expect a horizontal component to the resulting motion.
Quote from: CraigLieb on 05/21/2014 06:47 pmAny concerns about the capsule being tilted ~30 degrees from vertical due to the parachute attach point being on the side? See picture(s) captured from the Drop test video. Firing off the Draco Engines on landing may expect a horizontal component to the resulting motion. Surely a team that sends a ten story single engine rocket sliding 100m off to the side and back while ascending and descending, nulling velocity and rates at touchdown, can work out how to null rates and attitudes on a four engine-pair vehicle. Is there any doubt?
Surely a team that sends a ten story single engine rocket sliding 100m off to the side and back while ascending and descending, nulling velocity and rates at touchdown, can work out how to null rates and attitudes on a four engine-pair vehicle. Is there any doubt?
And Grasshopper and F9R don't throttle their engines?
And Grasshopper and F9R don't throttle their engines?This isn't a purely experimental vehicle like Grasshopper, but a prototype like F9R-Dev1. It is a systems test to make sure everything works together in a relevant environment. In NASA-speak, it is getting from TRL 5 to TRL 6.
"Propulsive Assist HoppingApproximately 400 gallons of propellant would be loaded into the DragonFly RLV for this test. During a propulsive assisted hop test, the DragonFly RLV would launch from a launch pad and ascend to approximately 7,000 ft AGL (firing engines for 12.5 seconds). Two parachutes would be deployed for the descent, the engines would fire for 12.5 seconds, and the RLV would make a powered landing on the launch pad. This operation would last approximately 60 seconds."
Quote from: simonbp on 05/21/2014 07:20 pmAnd Grasshopper and F9R don't throttle their engines?My point was balancing and attitude control of a differentially throttled multi engine vs a single engine gimbaled vehicle is marginally harder - because of control bandwidth. Not impossible and obviously achiveable. Thats all.