52

Commercial Crew awarded two providers for dissimilar redundancy. This is exactly why NASA decided to select two partners in the commercial crew effort. Having dissimilar redundancy is key in NASA’s approach to maintaining a crew and cargo aboard the space station and to keeping our commitments to international partners. It also allows our private industry ...


44

It seems like you are considering design for re-use as a flaw. The Super Draco engines are kept since they can be reused. They need them for abort, so unless they ditch them, they cost payload mass to support them. The CST-100 needs a new service module for each flight with new engines and whatnot, versus the much simpler/cheaper trunk the Dragon needs. ...


42

Scott Manley of the YouTube has a great video that addresses the extra level of the tower, located at the seven minute mark of a recent posting. Verbatim transcript from the video: So pad 39A is where they launched from. An historic pad... saw the launches of Apollo, Space Shuttle, but SpaceX took control of it in 2014 and they began modifying it for ...


37

The Merlin-1D engines are now tuned to use the super cooled fuel and oxidizer. Thus you would be running the engines in an out of normal state, if not using it the same as all other launches with warmer propellant. It would imply different software to handle the different performance levels. Last thing you want to do is run things differently, if you can ...


34

1.) Chairs needed to be custom molded / adjusted for the astronauts. There's stories of people sitting down in bathtubs of foam to create the perfect shape. That is an extra comfort of the Soyuz spacecraft. In NASA spacecraft, the seats were "one size fits all." One of the reasons is that the 'failsafe' modes of Soyuz - launchpad abort, ballistic reentry - ...


33

After the initial launch into orbit, the crew will be weightless, which will make things a little more comfortable. The Crew Dragon isn't as cramped as you might think; it has room for 4 crew members in the NASA configuration, so the crew will be able to move around a bit during the flight. Crew Dragon also has a toilet, according to this article (which also ...


30

It's an aerodynamics problem. SpaceX has designed both of their Dragon capsules to be inherently stable for reentry; should the capsule not be able to orient itself actively due to a Draco engine failure - it will passively orient itself during reentry with the blunt heatshield pointing forward, into the velocity vector. This minimizes risk and ensures the ...


30

As I understand the livestream, the most important thing was pressure equalisation and subsequent leak checking. I guess this could be done faster, but it's just not worth taking any risks on it. Imagine there's some problem with the docking securing. As long as there's no pressure between the hatches, this wouldn't be seen (no mechanical load). Now as you ...


29

The pressures of both the Dragon spacecraft and the ISS match the atmospheric sea level pressure of Earth, about 1 bar. But there are small inevitable tolerances of about some millibar or less. So there is a non zero pressure difference between the spacecraft and the spacestation. When air temperature in the closed spacecraft changes by only 0.3 K, the ...


25

It would be possible to design a check valve chain of high reliability of closing, but it would restrict flow and start to increase the risk of one valve sticking shut. You would probably also need pressure sensors between the valves to determine system state, so you end up with a large number of pipe to fitting joints that are potential leaks and a bunch of ...


25

It was a real failure (albeit triggered externally rather than accidentally), just not the only failure that can happen. and it is the worst case of a series of the most likely failure scenarios: multiple engine failure. If you want to test every conceivable way a rocket can fail, you're looking at thousands if not hundreds of thousands of possible failure ...


22

If you're just looking at it as a mass trade, then yes, you will definitely get a mass savings by replacing a portion of your propellant with a bag full of nylon. Depending on your speed, the nylon can have a much higher "Isp" than the rockets. However at the system level, there are other things to consider besides mass. First, parachutes are not "hyper-...


22

Two things. Human-rating a rocket is a long, expensive process See this questions for more informations What exactly does it mean to human-rate a rocket? As opposed to the escape system? Every single design aspect and component of your rocket will be studied and need to be approved for human launches. The rocket must also pass more stringent requirements ...


21

NASA has only contracted for flights with 4 astronauts, since the complement of the station is a maximum of 7 in the long term. The limit of 7 has many reasons, but some are for sleeping accommodations and life support systems capacity. Soyuz can carry 3. Thus the current complement of ISS is limited to 6 (two Soyuz craft) at the moment. Bringing 7 to ...


21

In addition to not wanting to change anything for crewed launches (as geoffc mentioned), adding crew to a fueled vehicle is a seriously dangerous move. If you look at the AMOS-6 failure you'll see that the launch abort system probably would have saved any crew that was already on board. However, if the crew was actively being loaded, we would have lost not ...


19

You seem to think they were testing in ideal conditions. That's as far from truth as you can get. The abort happened at the moment in flight with worst aerodynamical conditions (called maxQ), when booster flies still low enough in atmosphere for significant drag to be present, yet fast enough already. If Dragon can escape at this moment, it can escape at any ...


18

They didn't blow it up. They simply knew it would break up. A rocket is a very frail thing. It can only maintain it's structural integrity in forces it was designed to handle. When the Dragon left, the Falcon no longer had an aerodynamic nose cone. So supersonic wind forces pitched it sideways and the body of the rocket could not stand that force from that ...


16

Note that this answer refers to the final flight version of the Dragon V2. The first powered landings will be using parachutes before the system is validated for powered-only landing (see this article, thanks to Mark Adler for pointing this out). Parachutes are passive devices that slow the vehicle but do not steer it (some parachutes can steer a bit, ...


16

Ironically, the Soyuz vehicle has been taking a 'faster' approach to the ISS of late. Used to be a 1-2 day mission, and the new faster approach (tested on Progress vehicles first) is only about 4 hours. However, the 4 hour is less comfortable since they stay in the seats and suits the whole time, since there is not really enough time to get out, and get ...


15

When the space shuttle was in operation, it could carry as many as seven extra people, bringing the total population of the ISS up to ten. Three crew members is the standard permanent capacity of the space station, but the ISS can actually hold more. Ten is the working limit. In practice, the maximum number of people the shuttle carried was eight, and that ...


15

Musk indicated that Dragon 2 could be reused "with minimal rework and fueling" about 10 times between overhauls. This is the target number but these are early days. The previous ablative shield was dumped in favor of a more advanced design. The goal then, for heat shield, engines and other major components would be at Least 10 flights, in theory. Regards ...


15

E. Musk has answered this multiple times in interviews. This comes down to the economics of it. They are putting this entire system together to haul cargo, and the reusable portion is there to increase profits. They are putting in place a reusable restartable engine in order to have the maximum duplication of function for the components onboard. Previously ...


15

Now we've had the Crew Dragon In Flight Abort test, this can be answered more definitively. I've not found a stream where it's absolutely crystal clear, but in the NASASpaceFlight coverage, you can hear the countdown net in the background - sometimes being spoken over by Chris G. A timeline of critical events: ~T-45 minutes, the Crew Access Arm is ...


13

That is an anechoic chamber. An anechoic chamber ("an-echoic" meaning non-reflective, non-echoing or echo-free) is a room designed to completely absorb reflections of either sound or electromagnetic waves. They are also insulated from exterior sources of noise. The combination of both aspects means they simulate a quiet open-space of infinite ...


13

According to Aviation Week, it's 4 Merlin 1D engines per week. The same article says they're planning 12 Falcon 9 launches in 2014. In October 2014, SpaceX announced they'd completed the 100th Merlin 1D. According to that article, build tempo was 4 engines per week at that point, and 80 Merlin 1Ds had flown by then. This engine was slated to be flown on a ...


13

It's got to be hugely expensive to transport and erect a Falcon even if you don't intend to launch it. The potential for damaging part of the rocket in the test makes it even less attractive. Why use a real rocket if a truss suffices? After Apollo's first abort test from a low platform in the desert, they also did several in-flight abort tests by ...


13

What is the primary reason for SpaceX motion to have astronauts board Dragon before fueling up the rocket? From what I understand though, it shouldn't be necessary - Falcon 9 and Dragon 2 have enough payload capacity and delta-V to reach ISS with nominal payload, on non-supercooled oxygen. For better performance they are switching to supercooled fuel. To ...


12

Dragon V2 (Crew Dragon) uses 8 SuperDraco engines with maximum of 73,000 N thrust each. So, in theory, it could produce enough thrust to lift about 50,000 kg off the pad at thrust-to-weight ratio (T/W) of ~ 1.19. You need T/W larger than 1 to lift off the ground, and some more. T/W of ~ 1.2 is low for a launch vehicle and is usually closer to ~ 1.5, but let'...


12

First of all, Crew Dragon can actually be reused. NASA has agreed to permit reuse of both rockets and the capsule after the second longer-term mission. Of some note, the capsule was always designed to land with parachutes, they were only going to be a backup system. As it stands now, the propulsion is the backup system and the parachutes are the main system....


12

The orbital mechanics of satellites are independent from the mass of the satellite. As long as the sats mass is tiny compared to the mass of Earth. The total mass of the ISS is much larger than the mass of the dragon capsule itself, the same is true for the volume and surface of both. So the atmospheric drag of both changes only very little after docking.


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