How much speed could be shaved off of orbital velocity using the superdracos?If it was a substantial amount, wouldn't it reduce the loads on the heat shield quite a bit?
Quote from: Rondaz on 08/18/2018 06:40 amNASA, SpaceX Agree on Plans for Crew Launch Day Operations...If all goes according to plan, on launch day, the Falcon 9 composite overwrap pressure vessels, known as COPVs, will be loaded with helium and verified to be in a stable configuration prior to astronaut arrival at the launch pad....OK, if helium is loaded PRIOR to LOX, it means helium is at ambient T.
NASA, SpaceX Agree on Plans for Crew Launch Day Operations...If all goes according to plan, on launch day, the Falcon 9 composite overwrap pressure vessels, known as COPVs, will be loaded with helium and verified to be in a stable configuration prior to astronaut arrival at the launch pad....
I don't see why the helium would be at ambient. I would expect it to be supper chilled, possibly below the LOX temperature and "warm up" to the LOX temp as it is being loaded.
Quote from: smoliarm on 08/18/2018 11:51 amQuote from: Rondaz on 08/18/2018 06:40 amNASA, SpaceX Agree on Plans for Crew Launch Day Operations...If all goes according to plan, on launch day, the Falcon 9 composite overwrap pressure vessels, known as COPVs, will be loaded with helium and verified to be in a stable configuration prior to astronaut arrival at the launch pad....OK, if helium is loaded PRIOR to LOX, it means helium is at ambient T. I don't see why the helium would be at ambient. I would expect it to be supper chilled, possibly below the LOX temperature and "warm up" to the LOX temp as it is being loaded.
NASA, SpaceX Agree on Plans for Crew Launch Day OperationsQuoteNASA’s Commercial Crew Program and SpaceX are finalizing plans for launch day operations as they prepare for the company’s first flight test with astronauts on board. The teams are working toward a crew test flight to the International Space Station, known as Demo-2, with NASA astronauts Bob Behnken and Doug Hurley in April 2019. A key question the program and the company have been assessing is whether the astronauts will climb aboard the Crew Dragon spacecraft before or after SpaceX fuels the Falcon 9 rocket. NASA has made the decision to move forward with SpaceX’s plan to fuel the rocket after the astronauts are in place. While the agreement makes this plan the baseline for operations, it is contingent upon NASA’s final certification of the operation.“To make this decision, our teams conducted an extensive review of the SpaceX ground operations, launch vehicle design, escape systems and operational history,” said Kathy Lueders, manager of NASA’s Commercial Crew Program. “Safety for our personnel was the driver for this analysis, and the team’s assessment was that this plan presents the least risk.”Additional verification and demonstration activities, which include five crew loading demonstrations of the Falcon 9 Block 5, will be critical to final certification of this plan. These loading demonstrations will verify the flight crew configuration and crew loading timeline prior to Demo-2. After these conditions have been met, NASA will assess any remaining risk before determining that the system is certified to fly with crew.If all goes according to plan, on launch day, the Falcon 9 composite overwrap pressure vessels, known as COPVs, will be loaded with helium and verified to be in a stable configuration prior to astronaut arrival at the launch pad. The astronauts then will board the spacecraft about two hours before launch, when the launch system is in a quiescent state. After the ground crews depart the launch pad, the launch escape systems will be activated approximately 38 minutes before liftoff, just before fueling begins. SpaceX launch controllers then will begin loading rocket grade kerosene and densified liquid oxygen approximately 35 minutes before launch. The countdown and launch preparations can be stopped automatically up to the last moment before launch. In the unlikely event of an emergency at any point up to and after launch, the launch escape systems will allow the astronauts to evacuate safely.This timeline is consistent with the fueling procedures SpaceX uses for its commercial resupply missions and satellite launches.The crew launches of NASA’s Commercial Crew partners SpaceX and Boeing will return the nation’s ability to launch our astronauts from the United States to and from the International Space Station on American spacecraft.https://www.nasa.gov/feature/nasa-spacex-agree-on-plans-for-crew-launch-day-operations
NASA’s Commercial Crew Program and SpaceX are finalizing plans for launch day operations as they prepare for the company’s first flight test with astronauts on board. The teams are working toward a crew test flight to the International Space Station, known as Demo-2, with NASA astronauts Bob Behnken and Doug Hurley in April 2019. A key question the program and the company have been assessing is whether the astronauts will climb aboard the Crew Dragon spacecraft before or after SpaceX fuels the Falcon 9 rocket. NASA has made the decision to move forward with SpaceX’s plan to fuel the rocket after the astronauts are in place. While the agreement makes this plan the baseline for operations, it is contingent upon NASA’s final certification of the operation.“To make this decision, our teams conducted an extensive review of the SpaceX ground operations, launch vehicle design, escape systems and operational history,” said Kathy Lueders, manager of NASA’s Commercial Crew Program. “Safety for our personnel was the driver for this analysis, and the team’s assessment was that this plan presents the least risk.”Additional verification and demonstration activities, which include five crew loading demonstrations of the Falcon 9 Block 5, will be critical to final certification of this plan. These loading demonstrations will verify the flight crew configuration and crew loading timeline prior to Demo-2. After these conditions have been met, NASA will assess any remaining risk before determining that the system is certified to fly with crew.If all goes according to plan, on launch day, the Falcon 9 composite overwrap pressure vessels, known as COPVs, will be loaded with helium and verified to be in a stable configuration prior to astronaut arrival at the launch pad. The astronauts then will board the spacecraft about two hours before launch, when the launch system is in a quiescent state. After the ground crews depart the launch pad, the launch escape systems will be activated approximately 38 minutes before liftoff, just before fueling begins. SpaceX launch controllers then will begin loading rocket grade kerosene and densified liquid oxygen approximately 35 minutes before launch. The countdown and launch preparations can be stopped automatically up to the last moment before launch. In the unlikely event of an emergency at any point up to and after launch, the launch escape systems will allow the astronauts to evacuate safely.This timeline is consistent with the fueling procedures SpaceX uses for its commercial resupply missions and satellite launches.The crew launches of NASA’s Commercial Crew partners SpaceX and Boeing will return the nation’s ability to launch our astronauts from the United States to and from the International Space Station on American spacecraft.
Quote from: Roy_H on 08/18/2018 07:07 pmI don't see why the helium would be at ambient. I would expect it to be supper chilled, possibly below the LOX temperature and "warm up" to the LOX temp as it is being loaded.Do you not remember the Amos-6 F-9 exploding, destroying the pad, during a static fire? The cause is thought to be densified LOX, in the weave of the COPV, near its solidification point being frozen by colder Helium inside the COPV.Matthew
When it comes to Dragon 2 and its snazzy large-sized touchscreens -- how are these things able to stand up against the vibrations, shocks and stresses of space launch and re-entry? I'd imagine that such large thin screens (tablets?) would be particularly vulnerable to such forces.Are these primary control/viewing interfaces backed up by some kind of simpler and more rugged backup control scheme if they fail? Are these touchscreens the most modern choices available? Or could they one day give way to Augmented Reality (AR) projections on a spacesuit helmet visor?
Glass is pretty crazy-strong, and they've been using it for fighter jets that are designed to pull repeated 9G+ maneuvers for several decades now. Your cell phone, with its wafer-thin panel, isn't representative of the best the world has to offer for toughness; they're optimizing for weight and thickness.
Quote from: RotoSequence on 08/19/2018 02:36 amGlass is pretty crazy-strong, and they've been using it for fighter jets that are designed to pull repeated 9G+ maneuvers for several decades now. Your cell phone, with its wafer-thin panel, isn't representative of the best the world has to offer for toughness; they're optimizing for weight and thickness.Okay, but I'm presuming there are wafer thin tablet-style electronics behind that glass -- is that roughly accurate?Those could get rattled and disrupted during launch and lift-off. But I guess SpaceX would have tested against such conditions.Plus your touchscreens could get all smudgy during the course of a space mission - maybe some floating dirt could erroneously trigger a touch signal.I was also thinking that an AR-style mini-projection on a helmet visor might be the most compact, mass-saving and versatile solution. But I suppose there's the drawback of different personnel accidentally seeing different things when they're not all looking at a common viewscreen.
When it comes to Dragon 2 and its snazzy large-sized touchscreens -- how are these things able to stand up against the vibrations, shocks and stresses of space launch and re-entry? I'd imagine that such large thin screens (tablets?) would be particularly vulnerable to such forces.
Are these primary control/viewing interfaces backed up by some kind of simpler and more rugged backup control scheme if they fail?
Are these touchscreens the most modern choices available? Or could they one day give way to Augmented Reality (AR) projections on a spacesuit helmet visor?
When dealing with vibration, it's eliminating things that move that is important, and there is not much to move on displays.
Quote from: Coastal Ron on 08/19/2018 03:10 amWhen dealing with vibration, it's eliminating things that move that is important, and there is not much to move on displays.Okay, but a large enough screen is going to have some flexion...
...and should be affected by vibration, shouldn't it? The vibration and forces during launch and re-entry should be assumed to be extreme.
In that image with Musk I posted above, I guess it does look at least a few inches thick overall.
Projection technology allows you to achieve a large viewing surface area, without worrying about any resulting flexion or vulnerability due to size, since the viewing surface is effectively "dumb", and perhaps can even be an ad-hoc/improvised one.
The vibration and forces during launch and re-entry should be assumed to be extreme.
I assume you mean "flexing", but I'm not sure how such energy is transmitted that can cause the box the displays are in to twist and flex. If there is that much vibration I'd be more worried about the meat sacks onboard...
Liquid fueled engines don't have as much vibration as solid fuel engines, and as I pointed out the Soyuz flights are pretty smooth. Why do you think there will be a lot of vibration during normal ascents?
As to landings, I'm not sure what causes major vibration (or that it's a thing to be concerned about). Anyone want to chip in with some actual data on this?
They would have the display shock mounted in the enclosure, and the enclosure likely also allows the displays to operate in a complete vacuum.
Problem with projection displays is that what if something gets in the way of the projection, and what clean surface are they displaying the information on?
I think SpaceX thought through all of the alternatives, and what we see today is what they think was the best solution.
>Are we all worrying about something that doesn't need to be worried about?
