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 ...


45

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. ...


43

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 ...


42

These are mirrors. Even SpaceX's slick spacesuits have limited mobility, especially when the astronauts are strapped into the seats. The mirrors allow them to see corners of the spacecraft that they can't otherwise see because the helmet is in the way, they can't turn their head, they can't leave the seat, or similar. For example, if you try to look up, ...


34

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 ...


33

The contract between SpaceX and NASA required two demo flights (and SpaceX voluntarily did the in flight abort, notice Boeing is not doing that). They did an unmanned demo flight with Dragon C201, that launched Mar 2, 2019 and docked to the PMA/IDS on the ISS. Then they did the in flight abort, Jan 19, 2020 with the C205 capsule. Then they flew the Demo-2 ...


31

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 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 ...


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 ...


17

The previous one was also crewed (two crew) but it was called "demo" for some reason - despite taking astronauts to the ISS. The "some reason" that it was called "Demo" is that it was a demonstration flight, not an operational flight. How is the recent one different? It is not a demonstration flight, it is an operational ...


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 ...


12

All of the above, probably. Here are just a few of the things that must happen before liftoff. 35 minutes before liftoff, propellant loading starts on the Falcon 9 first and second stage. At this time, the only thing that can save the astronauts is the launch escape system. Which means, the launch escape system needs to be armed before that, then it needs ...


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.


11

If I remember correctly Spacex wanted Crew Dragon to land on legs, but NASA would not approve this design, only parachute landing. This is why the Engines are built in. Maybe NASA will approve this method one day. Source (partial): https://spaceflightnow.com/2017/07/19/propulsive-landings-nixed-from-spacexs-dragon-spaceship/


11

Orion is larger, has a life support rated for a few weeks, has a service module that will allow it real control around the Moon, and is rated for a return from the Moon. The closest direct comparison is the proposed Gray Dragon mission. This would carry two astronauts around the Moon and back, with no ability to orbit when it got there. It would require the ...


9

The main concerns, in the order they occur (but in increasing order of slowness of waiting) pressurization and leak checking, then temperature differences (from gasses changing pressure as it's filled in) leading to possible additional leaks. Then one side is opened and: dangerous gases air out - in zero-g they don't mix very quickly, and tend to ...


7

It seems NASA likes having two different options for flying humans in space. That's probably why they still have flights booked from Roskosmos. Competition is good. Boeing can probably still engineer the price down.


7

You are correctly parsing the information. There are two categories of duration. Running on its own power (solar) and other supplies, it can handle a week of free flight as your source indicates. Not sure what the specific limiting factors are. Possibly the solar arrays are not large enough for a complete charge, but are enough in combination with the ...


7

There are a few necessary activities and schedule considerations that contributed to needing 18 hours between undock and entry. Sleep Loading the Crew Dragon with returning (“down-mass”) gear, readying the capsule for undocking and maneuvers, and prepping the astronauts themselves is a full day of work, even for the three U.S. astronauts that were on the ISS....


6

The next module due to be launched to the ISS is Nauka. This is actually the backup FGB for Zarya, and is finally due to be launched this year. (We shall see, this saga has been going on for more than a decade now). It will contain crew quarters for at least one more, making room for the 7th resident of the station. It will dock to the Earth facing side ...


6

Space-X has a completely radical design and testing philosophy. NASA can't ignore it, because it produces results very quickly and costs much less than the traditional model. However, NASA also cannot fully commit to an untested paradigm. More generally, it's smart to diversify your portfolio if you don't know enough to pick the winners. There's also a ...


6

According to the Wikipedia page, Dragon 2 has a (pressurized) return payload capacity of 3,000 kg. This is definitely enough to bring back a few extra adult humans (though you may have to remove other important payload that was initially meant to be returned to earth). Your question however asks whether the extra astronauts would be able to hold on for dear ...


6

To answer the first question: Crew Dragon would reenter safely. Otherwise there wouldn't be a button in the Pyros section labeled "Jettison nose cone."


6

We'll ignore the 18 hours spent in orbit between Endeavour's undocking and the actual beginning of descent; I don't know what the crew were doing during that period, but it wasn't really part of the return-to-Earth process. I'm basing this answer on the times given Demo-2 return timeline posted on the NASA ISS blog on August 2, 2020, which as of this writing ...


6

Propulsive landing was the original plan for the Dragon 2, back when the Dragon 2 was also intended to maybe be used for Moon landings (Grey Dragon) and Mars landings (Red Dragon), where there is no or not enough atmosphere for parachutes. Plus, it would help commonize (is that a word?) knowledge between Falcon 9, Starship, and Dragon. However, both of those ...


5

This answer is taken from an article in Space Daily dated 02 Jun 2020. https://www.spacedaily.com/reports/AFRL_centrifuge_part_of_NASAs_history_making_launch_999.html About 18 months ago SpaceX/NASA astronauts on the Demo 2 flight were trained in a Dragon simulated flight deck while under g-loading reproducing those which would be experienced on actual ...


5

An enthusiast analysed the telemetry shown in SpaceX launches, which appears to show a significant throttle down for the Orbcomm2 mission. The question What makes the Merlin vacuum engine so deeply throttleable? discusses the throttling capability. However the capability doesn't appear to be used in most missions (including the crew carrying demo-1)


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