Hot answers tagged

51

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)....


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

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

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. ...


26

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 ...


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 ...


21

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.


19

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. ...


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 ...


17

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 ...


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

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 ...


15

Soyuz 10 used the launch escape tower from the pad.


15

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 ...


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.


13

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 ...


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 ...


13

Stargazer can definitely land with the rocket still attached. In fact Pegasus is usually loaded to Stargazer (with or without payload) at Vandenberg and then ferried to its actual launch site (CCAFS, Wallops, Kwaj, etc.) Stargazer is also able to abort a launch and return to the landing strip if there is anything wrong with the system. I believe this has ...


12

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 ...


12

From Encyclopedia Astronautica (emphasis by me): This configuration was selected only after considerable engineering angst. From the point of view of pulling the capsule away from the rocket in an emergency, positioning the capsule at the top of the spacecraft was ideal. But to use this layout with the living module concept, a hatch would have to ...


12

There were four types of intact aborts designed for Shuttle (not counting pad aborts). An intact abort is defined as one that returns the Orbiter intact to a runway. In order of least to most desirable: Return to Launch Site (RTLS) Trans-Atlantic Abort (TAL) Abort Once Around (AOA) Abort to Orbit (ATO) Only the ATO was ever performed in the Shuttle ...


12

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 ...


12

This is not a complete answer as I do not know the status of the parachute development, but here are some reasons a parachute is not needed: Ejected Data Recorders: These ~20 data recorders, literally Raspberry Pis with parachutes and waterproofing, all get the complete telemetry data from the test. This is made up of accelerometer, gyroscope, magnetometer ...


11

You'll have to define 'pad abort' as you are talking about both Apollo, Soyuz and the Space Shuttle. Apollo/Soyuz and Space Shuttle are vastly different vehicles, hence they have vastly different definitions of aborts. There were five RSLS (Redundant Set Launch Sequencer) aborts during the STS programme (on STS-41-D, STS-51, STS-51-F, STS-55 and STS-68). ...


11

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 ...


11

It will be difficult to find information about SpaceX costs, but Space Shuttle launch scrub costs have been published. NASA estimates every launch cancelled after fuel tanking has begun can cost as much as 1.2 million dollars. Endeavour endured five liftoff scrubs before successfully launching Wednesday at 6:03 p.m. (2203 GMT), though some of these ...


11

The Soyuz LES takes only the orbital module and reentry module with it, in order to maximize acceleration away from the launch vehicle. The diagram you link to in the question implicitly confirms this; the proportions of the separated section are such that the OM and RM fit neatly, and there’s no room for the SM. Per russianspaceweb: In 1965, developers ...


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