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52

Let's say you start rolling down from the top of a half-pipe skateboard ramp, and you plan to get back to your starting point. If you stop in the middle of the pipe, it is much harder to climb back up to your starting point then if you ride up the other side of the ramp and let gravity accelerate you back. Similarly, even if you planned to get into an orbit ...


50

All the other answers are great, but I think one explanation is still missing: how an interplanetary orbital transfer actually works in practice. The thing is, space is rather big, and things keep moving. At the same time, you're being tugged on constantly by all the other bodies in a planetary system (we can ignore other stars for interplanetary transfers)....


35

Well, I can refer you to the Range Safety Wikipedia entry: Two switches were used, ARM and DESTRUCT. The ARM switch shut down propulsion for liquid propelled vehicles, and the DESTRUCT ignited the primacord surrounding the fuel tanks. In the case of manned flight, the vehicle would be allowed to fly to apogee before the DESTRUCT was transmitted. This would ...


29

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 ...


29

Yes. There is a lot of good information in this presentation from the June 1966 Apollo Lunar Landing Mission Symposium relative to landing flight design including abort planning. The crucial figure is this one: which shows the capability of the ascent engine to abort all the way down to landing. It assumes a 4 second delay to separate the landing stage. ...


29

The shuttle stack broke up at ~73 seconds after launch of STS-51L. The Solid Rocket Boosters separated from the other elements and continued flying in a more or less stable manner (surprisingly). Air Force range safety personnel detonated the boosters at ~110 seconds after launch using the self-destruct system built into the boosters. (timeline reference) ...


28

14G sounds like a lot. To put it in context: the acceleration you can endure depends on the force vector. The position in which we can withstand G-forces best is forward (using the directions from the XKCD diagram), so spacecraft seats are placed to take advantage of this. When the rocket sits on the pad, the astronauts lie on their back. fighter pilots ...


26

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 ...


25

I assume that "halfway there" refers to being halfway along the transfer orbit from Earth to Mars, and that by "turn around" you mean reverse direction immediately. There is no reason a spacecraft "cannot" do this, but the reason it is entirely impractical is because of the propellant required to change the spacecraft trajectory. Aborting an Earth-to-Mars ...


24

The test they were doing didn’t require parachutes. Data-taking ended right after the capsule separated from the tower. Since the capsule’s behavior after that was not part of the test, it could be an inert item. To extend the test through parachute deployment, the capsule would have to be much more complex with the parachutes, deployment system, and a ...


22

Imagine a colonoscopy for a rocket engine. You go in with a flexible light pipe that has a camera on the end. (Engine is nicely sedated, usually). It looks around, cuts out any polyps it sees, oh I mean obstructions. So if a valve failed to open/close, they can see that without taking it all apart.


22

Thrust termination is the goal of Range Safety in the event of an errant rocket. Rendering the boosters inert is considered secondary, when possible. The Range Safety Officers don't rely on the current positions of the vehicle to decide to terminate, but instead are looking at the IIP (Integrated Impact Point) on a map. The IIP is the point where the ...


20

After a nominal landing the crew is waiting for a go from the ground to stay on the Moon. This was called the "Stay/No Stay for T1" and meant that there were no imminent issues requiring an immediate launch. So it was a commitment to stay for at least a few more minutes, until Mission Control could do a more detailed evaluation of the Lunar Module systems. ...


20

Some work on refueling capability for the SCA was done: Studies were conducted to equip the SCA with aerial refueling equipment, a modification already made to the U.S. Air Force E-4 (modified 747-200s) and 747 tanker transports for the IIAF. However, during formation flying with a tanker aircraft to test refueling approaches, minor cracks were spotted on ...


19

It was impossible to restart the engines in flight. If for no other reason, the pressure/temperature conditions for the "start box"1 were not met in flight. Also, Post Shutdown to Engine Ready was not a legal transition in the controller flight software. There were also considerations of engine drying (removal of residual water after shutdown), prelaunch ...


19

Lower orbits are faster, higher is slower, so by adjusting orbit altitude you can get an orbit that gains or lags until you are in position do execute a Hohmann transfer. The orbit period is around two hours and the velocities involved around a mile a second so 1000 miles does not have to take that long to close up. Especially if you get both craft change ...


19

No. I think this is actually the May 23, 1965 A-003 test, described in my answer to the question, Could a spacecraft spin so fast that it spontaneously deconstructs? Notice that the rocket and Apollo CM are spinning. That isn't supposed to happen. In A-003, improperly installed gyros caused the vanes on the fins to deflect fully in one direction, imparting ...


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

There is a detailed list here of everything that needed to be done for a scrubbed Saturn V launch, which gives an idea of the scale of the problem. Lots and lots of individual tasks to ensure the booster is still safe and stable. Get the crew out and safe everything Drain the propellants from the booster (they usually can't be left fuelled for a prolonged ...


17

For the shuttle, technically the deorbit burn could be aborted, but the window to do so was extremely limited. Once the deorbit burn was started, one of the key parameters monitored by the crew was the current height of perigee "HP" displayed on the maneuver display. This was a number in nautical miles and would have started out roughly equivalent to the ...


16

Soyuz 10 used the launch escape tower from the pad.


16

According to a Wikipedia article Apollo missions had multiple abort modes: Pad abort - If an emergency occurred during the last few minutes before launch, the launch escape system could pull the command module away from the rocket stack. Mode I - Would have been used during Stage I burn and would have used the lauch escape system to pull the command module ...


16

There were specific procedures for an abort at any time during the powered descent and after landing. The abort case at the planned time of landing (about 12 minutes after PDI) is covered in this chart: It is from the LM Rendezvous Procedures - G Mission PDF page 78. It's a bit crowded, but it shows the relative profile between CSM and LM, centered on the ...


15

It seems the most likely reason is that at T-10 seconds, anything that is a serious enough issue to abort should be caught by the computer, and aborting mid-stream could cause larger issues. Take a look at this video of the last 10 seconds. Here's what I can see happen: T-6 Water comes out for sound suppression on surface T-3 Engine ignites The last ...


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 ...


15

There are no published/proposed abort modes for ascent. We can speculate that some incidents can be survived by letting Starship tumble free and light it's own engines to burn to a low orbit or land depending on altitude and velocity, but that capability has not been proposed by SpaceX. Landing redundancy is provided by carrying 7 deep throttling, sea level ...


15

From the article: Tuesday’s launch was more focused on testing the launch abort system itself. The parachutes on Orion have been tested 47 times.


14

Dry mass of the first stage from SpaceFlight101 suggests 25,600 kilos. Dry mass of the second stage is 3,900 kilos, and 92,670 kilos fueled. Ignoring payload, that is one heck of a top heavy vehicle, an empty first stage, and a fully fueled second stage, almost 4 times the mass in the second stage. The current control facilities (Cold gas thrusters, Grid ...


14

My reading of the function of the SRB manual separation control is that it would not actually trigger a separation while the boosters were firing (bold mine): SRB separation is normally performed automatically by the onboard GPCs; however, the flight crew can command separation through use of the SRB separation switches on panel C3. The SRB separation auto/...


13

The report via Tweet from Elon Musk initially is that a slower than usual ramp up of thrust caused the flight computers to abort. Elon Musk via Twitter: Launch aborted by autosequence due to slower than expected thrust ramp. Seems ok on closer inspection. Cycling countdown. There is reported leeway in relaxing some of the sensitivity on this issue ...


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