Quote from: simonbp on 04/28/2011 07:58 pmOK, B$ detector going off big time on the Mars landing aspect. The only way to make that work is with a parachute to get you subsonic first, and then turn on the engines (rockets cannot fire into a supersonic flow)....That's not true at all. Rockets can, in fact, fire into a supersonic flow. For supersonic retropropulsion with just a single engine, there is a marked reduction in drag, but for canted side-mounted rocket engines like this, there wouldn't be a reduction in drag.
OK, B$ detector going off big time on the Mars landing aspect. The only way to make that work is with a parachute to get you subsonic first, and then turn on the engines (rockets cannot fire into a supersonic flow)....
If that center J-2 on Apollo 13 ripped out from its mount and torpedoed through the entire S-II stage (as some speculated could have happened had it not shut down first), I wonder if the gentle SPS acceleration would have done the trick.
Right, escape being possible doesn't mean it's guaranteed to save you in every scenario. This is true whether you have high power escape motors or not.
I'm not saying that SpaceX system couldn't be better than what Apollo had, I'm just disappointed by the needless conflation of an *escape tower* with an *escape system*. SpaceX should know better.
Looks like the vision is for Martian powered landing. What really interests me is at 1:18 you get a view of a Spacex "space barge" holding cargo and another Dragon spacecraft for accent. Are those engines underneath the Dragon for the martian accent phase?
Screencap (cropped) from the 720p HD version at 1:17, taken in fullscreen mode.
Quote from: hop on 04/28/2011 08:36 pmbecause after that escape was possible without the tower. If that center J-2 on Apollo 13 ripped out from its mount and torpedoed through the entire S-II stage (as some speculated could have happened had it not shut down first), I wonder if the gentle SPS acceleration would have done the trick.
because after that escape was possible without the tower.
Quote from: Chris Bergin on 04/28/2011 05:13 pmAttached is the SpaceX press kit.And the actual press kit... http://www.spacex.com/downloads/20110428-spacex-sts134.pdf
Attached is the SpaceX press kit.
Gentle?
Link doesn't seem to work, goes to a 404 for me. Can someone attach it here?
Quote from: Downix on 04/28/2011 09:08 pmGentle? Gentle compared to the LES acceleration. Not when used as normal main propulsion.Quote from: 2552 on 04/28/2011 09:11 pmLink doesn't seem to work, goes to a 404 for me. Can someone attach it here?Hmm. Still works for me. Have you tried copying the URL text manually into the address bar?
Here.
Maybe SpaceX took it down but it's still in your browser cache, so the link still "works" for you?
Quote from: mr. mark on 04/28/2011 05:21 pmLooks like the vision is for Martian powered landing. What really interests me is at 1:18 you get a view of a Spacex "space barge" holding cargo and another Dragon spacecraft for accent. Are those engines underneath the Dragon for the martian accent phase?Quote from: 2552 on 04/28/2011 11:31 amScreencap (cropped) from the 720p HD version at 1:17, taken in fullscreen mode.
Quote from: Robotbeat on 04/28/2011 06:14 pmAnd to be honest, I agree with the CCDev2 reviewer that using a hybrid rocket is risky for abort. Dreamchaser is cool, but is more difficult to develop.I don't see it as risky, it depends on the particulars of the hybrid system doesn't it? I made one, once, which was Hypergolic, so no concern over ignition there.*edit* Come to think of it, my particular design would not be smart for the Dream Chaser in any case, as I used a 5% formula of Chlorine TriFlouride as the oxidizer. That stuff is dangerous in the highest degree, so falls under the "Don't do this at home kids" category.
And to be honest, I agree with the CCDev2 reviewer that using a hybrid rocket is risky for abort. Dreamchaser is cool, but is more difficult to develop.
Quote from: Downix on 04/28/2011 06:53 pmQuote from: Robotbeat on 04/28/2011 06:14 pmAnd to be honest, I agree with the CCDev2 reviewer that using a hybrid rocket is risky for abort. Dreamchaser is cool, but is more difficult to develop.I don't see it as risky, it depends on the particulars of the hybrid system doesn't it? I made one, once, which was Hypergolic, so no concern over ignition there.*edit* Come to think of it, my particular design would not be smart for the Dream Chaser in any case, as I used a 5% formula of Chlorine TriFlouride as the oxidizer. That stuff is dangerous in the highest degree, so falls under the "Don't do this at home kids" category.In my view, the problem with a hybrid for abort is start up time. You really want something that can deliver 100 ms or less to full thrust, and all hybrids I've seen are more like 1500 ms.
Quote from: HMXHMX on 04/28/2011 09:42 pmQuote from: Downix on 04/28/2011 06:53 pmQuote from: Robotbeat on 04/28/2011 06:14 pmAnd to be honest, I agree with the CCDev2 reviewer that using a hybrid rocket is risky for abort. Dreamchaser is cool, but is more difficult to develop.I don't see it as risky, it depends on the particulars of the hybrid system doesn't it? I made one, once, which was Hypergolic, so no concern over ignition there.*edit* Come to think of it, my particular design would not be smart for the Dream Chaser in any case, as I used a 5% formula of Chlorine TriFlouride as the oxidizer. That stuff is dangerous in the highest degree, so falls under the "Don't do this at home kids" category.In my view, the problem with a hybrid for abort is start up time. You really want something that can deliver 100 ms or less to full thrust, and all hybrids I've seen are more like 1500 ms.You've never worked with Chlorine TriFlouride then. That stuff is insta-on. (I did not have a fine enough fidelity camera when testing it, so all I can say is that it was faster than 200ms.
OK, B$ detector going off big time on the Mars landing aspect. The only way to make that work is with a parachute to get you subsonic first, and then turn on the engines (rockets cannot fire into a supersonic flow). Not impossible, but ends up with a completely redesigned vehicle. Plus (of course), you still need to get back up, which means a entirely separate vehicle. And there's no way you're landing on the Moon with it without a crasher stage to brake from LLO.
Quote from: hop on 04/28/2011 08:56 pmRight, escape being possible doesn't mean it's guaranteed to save you in every scenario. This is true whether you have high power escape motors or not.I agree and I'm not saying having a LAS would necessarily have worked in that case, either.QuoteI'm not saying that SpaceX system couldn't be better than what Apollo had, I'm just disappointed by the needless conflation of an *escape tower* with an *escape system*. SpaceX should know better.Maybe there's a fine distinction between "escape" and "abort" to be made? SPS could have aborted away from let's say a gracefully shut down stage, but it probably wouldn't have worked that well if the vehicle executed a RUD.In the end, this is all spin and I don't personally get too excited over it.
Yep, definitely looks like a separate MAV; Possibly 4 x Merlin-1 as the propulsion system. Likely the Dragons would be only descent and ascent vehicles, there would be a separate (Bigelow-designed?) orbital transfer vehicle.Talk is cheap and even CGI is cheaper than rocket engineering. However, I do suspect that this is SpaceX metaphorically throwing down the gauntlet: "If you won't, we will."
Are those engines underneath the Dragon for the martian accent phase?