SpaceX vs. Space Shuttle: NASA's Falcon 9 Astronauts Compare the Differences (spaceflightnow.com) 61
NASA astronauts Doug Hurley and Bob Behnken flew to the International Space Station on SpaceX's Crew Dragon. But they're also uniquely qualified to describe what it felt like, since both had also flown twice on NASA's Space Shuttle. So how did its solid-fueled booster rockets during the first stage of lift-off compare to SpaceX's liquid-fueled booster rockets? A Slashdot reader shares their answer, in an article from Spaceflight Now:
The Crew Dragon astronauts said the ride on the Falcon 9 rocket was smoother than the space shuttle for the first couple of minutes... "[O]ur expectation was, as we continued with the flight into second stage, that things would basically get a lot smoother than the space shuttle did. But Dragon was huffing and puffing all the way into orbit..." Behnken said. "A little bit less Gs, but a little bit more alive is probably the best way I would describe it." Hurley said, "it was very similar to what you saw in the Apollo 13 movie, where they staged from first to second stage... "That was the highlight of the ascent for me," Hurley said.
"So totally different than shuttle," Hurley said. "It was smooth. It got a little rougher."
The Dragon's automatic docking with the space station felt more gentle than expected, Hurley said. "The thing that really stood out to both us — and we mentioned it was soon as we docked — is we didn't feel the docking," he said. "It was just so smooth, and then we were docked. In shuttle, you felt a little bit of a jolt, nothing real heavy, but you felt it."
Hurley and Behnken also had positive reviews for their SpaceX-made pressure suits. The astronauts wore them during launch and docking, and will put them on again for their return to Earth — expected in late July or August. "They're custom designed and custom fitted, so they're very comfortable," Hurley said. The astronauts said taking off the suits and putting them on in space, without the effect of gravity, was much easier than on Earth. "We'd have to give the suits a five star rating," Behnken said....
"For us — as the test pilots, so to speak — we're there to evaluate how it does the mission, and so far it's done just absolutely spectacularly," Hurley said.
"So totally different than shuttle," Hurley said. "It was smooth. It got a little rougher."
The Dragon's automatic docking with the space station felt more gentle than expected, Hurley said. "The thing that really stood out to both us — and we mentioned it was soon as we docked — is we didn't feel the docking," he said. "It was just so smooth, and then we were docked. In shuttle, you felt a little bit of a jolt, nothing real heavy, but you felt it."
Hurley and Behnken also had positive reviews for their SpaceX-made pressure suits. The astronauts wore them during launch and docking, and will put them on again for their return to Earth — expected in late July or August. "They're custom designed and custom fitted, so they're very comfortable," Hurley said. The astronauts said taking off the suits and putting them on in space, without the effect of gravity, was much easier than on Earth. "We'd have to give the suits a five star rating," Behnken said....
"For us — as the test pilots, so to speak — we're there to evaluate how it does the mission, and so far it's done just absolutely spectacularly," Hurley said.
It's a little heavier (Score:1)
The Shuttle orbiter was ~8.5 the dry mass of the Crew Dragon capsule. So yeah, I'd expect you'd get a little more of a jolt trying to dock something almost a magnitude heavier, I don't know why an astronaut who flew both would find the docking differences "surprising".
Re:It's a little heavier (Score:5, Funny)
Yeah, those guys are definitely ignorant on this topic. Thank you for setting them straight.
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I don't know why an astronaut who flew both would find the docking differences "surprising".
After roughly a decade passing since they did it last there could have been some faded memory. Also, think of the mass difference of the Dragon to the ISS compared to the mass difference of the Space Shuttle to the ISS. If there was a big jolt in docking something as heavy as a Space Shuttle then slamming something as light as the Dragon could be thought to be far more jarring.
Bad car analogy time...
If I have a trailer that I've been pulling around with my big old heavy truck and I had the experience of i
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The actual correct answer is near the bottom of the thread. Different docking hardware.
https://science.slashdot.org/c... [slashdot.org]
It would be the other way around. (Score:5, Insightful)
If you are in a large thing docking, the large mass of the item would damp the impact. You'd feel it less in the heavy shuttle.
With the light Dragon, any impact would be directly felt. So the way the rocket docked without a noticeable impact is noteworthy.
It''s a bit like what you'd feel if you were in a bus that collided with a bicycle, compared to what you'd feel on a bicycle that collides with a bus.
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Maybe this is naive but I thought the objective of any docking maneuver is to make contact at the smallest possible delta. The relative mass of the spacecraft to the station doesn't mean anything if you achieve that. The smaller delta at contact the less "jolt".
I suspect the difference has more to do with the superior maneuvering capability of the more modern spacecraft than anything to do with mass.
And this is more than just for comfort of the passengers. Any force imparted by the docking ship at c
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Also, extra momentum in docking can result in stresses in places that really shouldn't have any, leading to all sorts of gremlin-like malfunctions and possibly leaks with enough repetition.
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Wow. You do realize that weight has absolutely nothing to do with the "jolt" felt by the astronauts right? The "jolt" is deceleration and sound produced by the impact. Nothing to do with weight, everything to do with speed at contact.
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Yes, the jolt is caused by sudden deceleration. Are you really claiming deceleration has nothing to do with mass?
It's not just speed at contact, it's total kinetic energy (eg, momentum) at contact. Which is mass times velocity.
If you're in a heavier vehicle, you will decelerate more slowly, which will feel "less jolty". To illustrate, if a bicycle is in a head-on collision with a truck, which person feels more of a jolt? The relative velocity of the impact is the same, the only difference is the mass.
Mass doesn't matter at all here (Score:1)
Are you really claiming deceleration has nothing to do with mass?
In space the amount of deceleration is entirely dependent on what the thrusters are doing when.
Mass only factors in in determining how fast you can alter direction and speed, but at docking speeds we are talking about counter-acceleration way below what the thrusters are rated for.
That's why they felt nothing, because the thrusters were able to deliver a perfect counter to motion at the time of docking so that no deceleration was felt (or very
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Yes of course it comes down to the thrusters.
But the point is simply that *all things being equal*, a lighter vehicle would feel more of a jolt.
Like, they felt a jolt with the space shuttle. A lighter vehicle would've felt MORE of a jolt in that same situation, not less (which is what slyborg was claiming).
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The shuttle likely couldn't fire its thrusters hard enough to slow its relative velocity enough without damaging ISS.
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Oh, never mind. The correct answer is near the bottom of the thread.
https://science.slashdot.org/c... [slashdot.org]
Re: It's a little heavier (Score:2)
So yeah, I'd expect you'd get a little more of a jolt trying to dock something almost a magnitude heavier,
That's because you never thought* about - much less even studied - physics.
*Clearly you thought** that you thought about it.
**You only thought those were thoughts - the 'thinking impaired' always do.
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Where does it say they were surprised by it?
The two aren't mutually exclusive anyway: you can simultaneously understand the physics of it all and still be impressed that the docking was so smooth.
did they actually fly it at all? (Score:3)
Did the astronauts actually do any of the controlling of the capsule or was it all basically push button automatics doing the work?
It sounds like it the latter.
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well, they're like passengers with an incredibly long to-do list. sure, they're not steering the ship or pushing any buttons to fire the engines, but there's 650 steps they have to do in order to get the mission done.
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Re:did they actually fly it at all? (Score:5, Interesting)
Did the astronauts actually do any of the controlling of the capsule or was it all basically push button automatics doing the work?
It sounds like it the latter.
I watched the whole launch and docking live. It took a while to dock. During the docking, while they were maneuvering ways, the astronauts did some free flying as part of the Dragon testing.
They then went back to the flight computers for docking.
It took about 2-3 hours realtime for them to go the last few thousand meters, I was wondering how long it would take if there was some kind of emergency.
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It took about 2-3 hours realtime for them to go the last few thousand meters, I was wondering how long it would take if there was some kind of emergency.
You mean how they could shorten the docking if there was an emergency on the Dragon? If there was an emergency then they'd likely abort the docking and come back to Earth. I doubt the ISS is equipped to handle any emergency on the Dragon. If there was a leak of the air on board then docking with the ISS could just bring that leak to the station. If there was some kind of medical emergency then there is one man down on the crew and docking with an untested automated docking system, this makes docking ris
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It took about 2-3 hours realtime for them to go the last few thousand meters, I was wondering how long it would take if there was some kind of emergency.
You mean how they could shorten the docking if there was an emergency on the Dragon? If there was an emergency then they'd likely abort the docking and come back to Earth. I doubt the ISS is equipped to handle any emergency on the Dragon. If there was a leak of the air on board then docking with the ISS could just bring that leak to the station. If there was some kind of medical emergency then there is one man down on the crew and docking with an untested automated docking system, this makes docking risky. Other mechanical problems could also mean a loss of the ability to dock safely.
It sounds like future missions like this will have crews of three or four, perhaps as high as six or seven. This adds redundancy on the crew so one injured or sick member of the crew is less of an issue, there will still be two people to take the controls. Mechanical problems with this many people changes the math, there's more lives at risk and so there could be more urgency to dock vs. abort to Earth. And, again, more crew to manage the problem so someone can look at a leak (or whatever) while another checks life support (or whatever) and there's still two people to pilot the ship.
Most of all, as I understand it, in the future there would be a tested automatic docking system so, perhaps, even if everyone on board was unable to function for some reason they could just let the computer dock and then the ISS crew can help clean up and check on what went wrong. This is possible, but I believe unlikely, this could bring to the ISS something that they could not handle when an abort to Earth means being greeted by trained fire and rescue as well as a breathable atmosphere.
I recall that NASA demanded the ability to abort to Earth at every phase of the mission. Perhaps with a ship that would berth (as opposed to dock) with the ISS, where the ISS reaches out and grabs the ship, there might be an option to abort to the ISS is case of some failure.
Good question, and I'm only thinking of the options as I understand them.
We're cool. I was wondering about an emergency on the ISS.
I think there is still a Soyuz docked somewhere and there are 6 or so people on the ISS at the moment.
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Other than some testing of the manual controls before docking it sounds like it was all on autopilot.
They had to know how to dock manually in case of some computer screw up so they had to test the controls and be trained how to dock before NASA would allow them to dock. At least that's what I recall. I probably saw this on the Everyday Astronaut YouTube channel somewhere.
https://www.youtube.com/channe... [youtube.com]
Re: did they actually fly it at all? (Score:2)
While there are still manual docking controls in case of serious issues, it was done by flight computers.
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Not Surprising (Score:2)
It shouldn't be that surprising. The Falcon 9 and Space Shuttle were two very different beasts and have different flight patterns. The Space Shuttle had additional thrust during the first part with the two solid-fuel boosters vs the Falcon 9 with no boosters, just 9 engines. Also the Dragon had some dampening between it and the Falcon while the Shuttle had no dampening, it's three engines effectively was the first and second stage rockets.
As for the second stage, the Falcon second stage has one of the same
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Would the difference in perception of the thrust characteristics - i.e. the "feel" - between shuttle and Falcon be largely the ability to finely control the liquid-fuel rockets, as opposed to the all-or-nothing of the solid-fuel design?
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Would the difference in perception of the thrust characteristics - i.e. the "feel" - between shuttle and Falcon be largely the ability to finely control the liquid-fuel rockets, as opposed to the all-or-nothing of the solid-fuel design?
I would think that any autopilot would take into consideration the type of fuel, thrust, etc. I'd be willing to bet that one of the big differences would be the amount of measurements and calculations that modern computers can handle. In other words, a faster computer can take more input from the sensors allowing for much more accurate positional data.
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Another old paper from 1967 https://www.jhuapl.edu/Content... [jhuapl.edu] particularly Figure 3.
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Just FYI, the summary does not say anyone was surprised. But thanks for your explanation anyway.
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Bonk? (Score:1)
Having your heads smack on the control panels doesn't seem like a good plan. There should've been mountable buffer pillows.
Slashdot Commentators Smarter than Astronauts! (Score:5, Funny)
I'm really quite amazed by how many of you obviously know a great deal more about all of this than the astronauts with 35 years experience and the NASA engineers who designed all this. /s
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I'm surprised at all the posters who are surprised.
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I'm really quite amazed by how many of you obviously know a great deal more about all of this than the astronauts with 35 years experience and the NASA engineers who designed all this. /s
It's like when my 13 year-old niece insisted that she knows how her cell phone, wifi and the Internet work better than I do -- someone with 30+ years as a software developer, system and network administrator on everything from PCs to a Cray-2. Grrrr ....
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In fairness to your niece the average adult that she encounters probably knows little more, and probably a lot less, than she does about those things. Does she know you have 30 years experience with technology and that not all adults should get lumped into the Boomer bucket?
I get what you're saying, but she's not tech oriented and I know she doesn't understand this stuff and, yes, she knows that I'm an IT professional (as is her father and her aunt). In the case I'm referring to, she wanted to do something on her phone that she wasn't allowed to do and was trying to argue that I (and her parents) were wrong and she was right. She just wanted to be right so she could do what she wanted. In the end, she got her phone taken away for a week.
I had a similar argument way back wh
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I bet she knows the UI's better than you because she's used them a lot more. That's a diff issue than how chips work.
Not really a surprise (Score:3, Informative)
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The original space shuttle was a dangerous Rube Goldberg contraption whose primary characteristic was its adverse impact on tapayers' wallets.
It's main contribution to aerospace has been as a hard lesson on how *not* to design launch vehicle.
Re:Not really a surprise (Score:5, Interesting)
The original space shuttle was a dangerous Rube Goldberg contraption
People loooove ragging on the shuttle.
It killed more people than any other launch vehicle. It also put far more people into orbit than any other launch vehicle. The only other remotely comparable thing was Soyuz, and if you look at the ratio of people killed vs attempts at putting people in orbit and back again, the shuttle was a bit worse, but not actually that much. I crunched the numbers once, it was something like 30%.
If Space-X isn't much, much safer, it would be a travesty. This is not an indictment of the shuttle: they've have 40 year of advancement in engineering, safety, rocketry and spaceflight to take advantage of. It *ought* to be much much better.
Re: Not really a surprise (Score:2)
When I did the math st shuttle retirement the shuttle had a 1.8% death rate. For 14 deaths it launched ,700+ people into orbit.
Soyz a to the same time launched 200 odd people and killed 3-4 for a rate of 1.6
Now the soyz numbers have changed. But no where near the shuttles amount.
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But no where near the shuttles amount.
You said the shuttle was 1.8% and Soyuz was 1.6%. I'd call that "pretty close" not "nowhere near". Or did you mean the total numbers launched? If so, yeah, 200 is indeed nowhere near 700, but it's the closest to the shuttle by a long way.
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The Shuttle's barely acceptable "safety" came at the cost of almost completely rebuilding the vehicle after every mission. This was not the design goal, and they should have abandoned the project as a complete failure after the first few launches when they realized that it had utterly failed in its objective of re-usability.
There were opportunity costs involved: Launching each person on the shuttle costs many scores of $millions more than using a couple of expendable human launch rockets plus an expendable
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but because they went back to proven 1960s-era features such as a launch abort system and a small simple heat shield.
I wonder if SpaceX engineers also have advantage of being younger and not carrying baggage of Apollo and Shuttle. Orion design was chosen as "simple safe soon" but this Apollo-on-steroids is years behind schedule and prohibitively expensive.
Also during Shuttle development in 1970s, NASA was undergoing austerity. Though hiring began to go up in later 70s but there was still an ongoing reduction of infrastructure and accelerated in 1990s. i.e. always been an ongoing push to close a NASA Center or two. There
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There were opportunity costs involved: Launching each person on the shuttle costs many scores of $millions more than using a couple of expendable human launch rockets plus an expendable heavy lift rocket for the cargo.
You don't know that to be true. Look at the SLS, it's designed just how you describe - expendable rocket carrying a traditional capsule and it's going to cost $1 billion per mission. Since they are using the old Shuttle engines as well as the booster technology it should have been cheap to develop and it's still more expensive than any launch vehicle out there. Just think of how much it would cost if they had to build it from scratch. If NASA had developed a capsule rather than a shuttle in the 70's it
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NASA didn't have to develop anything new. There were many existing expendable rockets they could buy off the shelf, and they already had a couple of viable capsule designs. They should have just done incremental improvements over the years similar to the Soviet space program.
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You didn't actually address any of my points. You talk about "proven 1960s era features", like that actually exists. The only thing that remotely fits that description is Soyuz and that doesn't have a much better death rate than the shuttle.
It's debatable whether they should have cancelled the shuttle or doubled down. These days space X has found that reusable rockets are cheaper than not, so that's not a terrible idea.
It's also a kind of absurd claim that engineering hasn't improved in 60 years and there a
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I told you exactly which 1960s features. Let me repeat: A launch abort system, and a reasonable heat shield (as opposed to 30,000 fragile handmade tiles that had to be individually tweaked each launch).
These both have certainly been proven in flight in the real world. You're just choosing to not comprehend what I said.
Unlike the space shuttle, SpaceX has apparently succeeded in reducing costs using reusability. Good for them: Their project is working and they don't need to cancel it and go back to expendabl
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Unlike the space shuttle, SpaceX has apparently succeeded in reducing costs using reusability. Good for them: Their project is working and they don't need to cancel it and go back to expendable launches.
So far - it's not done yet, until it can return people back to Earth. The probability of fail of that is very low, but until it's completed a round trip of putting people on to the space station AND bringing them back - it's not done the same functionality.
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Unmanned Dragon capsules have safely returned to Earth over a dozen times, a number of them with refurbished capsules. So while you're right that it hasn't been proven with human passengers, a manned return flight is more or less tying it up with a bow.
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These both have certainly been proven in flight in the real world.
Proven in that they yielded a slightly lower death rate than the Shuttle but not drastically so.
So proven.
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The Soyuz incidents were due to a tangled parachute and a jammed air valve, both of which happened on early versions during the corner-cutting era of the space race (the same kind of corner cutting that led to the Apollo fire). Both problems were fixed many decades ago.
Neither incident had anything to do with the features I was discussing.
The problems with the Space Shuttle could not be fixed. They were baked into the design. The only way to try to address the problems was to do even more rebuilding and ins
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People loooove ragging on the shuttle.
I'm one of those people. Safety statistics aside, the launch abort options were inadequate. Particularly before the Challenger Disaster. It's uncertain if many of them would actually work, particularly RTLS.
"RTLS requires continuous miracles interspersed with acts of God to be successful"
-STS-1 commander John Young
Shuttles used an older, simpler, docking system (Score:5, Informative)
It's not really surprising that the astronauts felt the docking was smoother because the NASA Docking System that they were docking to was actually on the International Docking Adapter (IDA) ring that was fitted to the original Russian-based APAS system used for the space shuttles. The APAS docking system depended on ramming force to mechanically connect. The new NASA Docking System on the outside of the IDA was based on an earlier design called the international Low Impact Docking System (iLIDS) whose soft capture ring integrates a load sensing ring which senses loads and, using a complex control algorithm, dampens oscillations and maintains horizontal alignment between the mated vehicles.
https://en.wikipedia.org/wiki/... [wikipedia.org]
https://ntrs.nasa.gov/archive/... [nasa.gov]
Useful analogy (Score:2)
It's like the difference between commuting to work in a Prius and driving a bro-truck back and forth for no good reason.