Col. John Stapp proved it's not how much deceleration you encounter, but how long it lasts. A few seconds at 12g might be bad, but a lot better than sustained 4g.
not sure how, if I try the same thing my parachute rips off, I have to arm them much higher up so they open early and slow me down before opening fully.
Thank you for the video. I was one of those who asked what a ballistic re-entry meant. This video really helps me - I still don't fully understand what is happening but now you have shown me in an animation what happens I can replay it in my mind until I understand what is happening. Based on what you have shown it sounds like one of the main factors is the altitude, since the re-entry vehicle is moving at a high speed in a still relatively high density atmosphere the deceleration(acceleration really) is higher than if it was re-entering the atmosphere from 'space' where it can decelerate at a slower rate due to the atmosphere being less dense.
sort of got it. What ballistic re-entry means is that the capsule is not doing any maneuvering to try and control it's decent, instead it "flies as it flies", it is un-controlled (which sounds scary hence why they say ballistic trajectory or ballistic decent), doesn't matter what altitude it is descending from. What Scott is showing us is WHY you would want a capsule to normally control it's decent (because it can reduce g-loading), he is also showing what can happen if the capsule tries to control it's decent improperly (the super fast and steep entry that resulted in really high g-loading). He then showed us how a ballistic sub-orbital reentry could be harder on the crew than a nominal re-entry from orbit (this is due to the altitude, as you said, even though returning from orbit means you start off going faster).
This was a very well explained video. I enjoyed being led through with examples and numbers and side-by-sides. Obviously lots of planning went into it.
When I studied space dynamics as an undergraduate that was one of the concepts that I really found surprising. That you could fly the space capsule into atmosphere.
I believe the details on how soyuz capsule controls roll-pitch-yaw during re-entry (shifted CoM) may confuse those who are unaware of the difference between controlled and ballistic trajectories - the main idea of the vid is right on point: at that alt you do not need to control capsule - so after abort sequence they let it fly as it flies - and call that ballistic trajectory (which actually means 'let it fly as it flies')
It kinda makes sense. I imagine the astronauts when thinking about performing the ballistic reentry "Huh... we just had an abort due to a booster failiure... let's just keep this thing doing what it has to do, better if we don't try space cowboy with it".
@@ewthmatth you do not... Once it sits in air flow stream its shape does it. There is no control. Again, at higher altitude you can control it, at altitude/speed they've aborted there is no such possibility. It's not a choice its posr-factum name for 'letting it fly as it flies'.
Hi Scott, Another great presentation as always. Back on April 19, 2008, So-yeon Yi, Peggy Whitson and Yuri Malenchenko, aboard Soyuz TMA-11, are said to have suffered through up to 10 G’s during a ballistic re-entry. Whitson said "I saw 8.2 G's on the meter and it was pretty, pretty dramatic," Also the ballistic re-entry caused them to land about 260 miles short of the targeted landing site. Regards, Tom Charlton
Can't get enough! I love these videos explaining the launch failure. It is not a good thing this happened, but the silver lining is the education of how things work on such a failure. And, of course, the education part of, "Space is NOT a nice place, and getting out there is REALLY freakin' HARD!"
I always put a service module(the one with the door) under the command module with science stuff and extra rcs fuel then the heat shield and I offset the center of mass with how I arrange everything, and I also use 2 small side parachute offset to the side so In case I have a heavy load, like full science equipment and extra rcs, the Impact will be on a corner and allow the craft to roll out extra speed. I have been using this design for as long as I remember the service module being in the game and it never failed me, even reentering from a free return from minmus with steep entry
İ just completet my first mun mission and then i was going back to kerbin but during the reentry i realised i forgot the parachutes on the lander! But my professional piloting skils and the landing asist engines on the lander saved 2 kerbals in that day. ( sory for my bad english im Martian )
I did something similar thought about leaving them in orbit and sending up a rescue mission but noticed I had a stage with a 1/3 tank of propellant and a thrust greater than 1 to 1 so I decided to come in with the stage still attached and try to land with it.
Will you do a video on the differences between ablative materials for reentry as opposed to ceramic thermal tiles and how each one is best suited for what kind of vehicle is used to reenter the atmosphere? That would be interesting, at least in my opinion lol. Bill & Bob Kerman both want to see it as well...so thats always nice. 😁
Great stuff! Not sure if anyone here watches the Mind & Machine channel but they had Naveen Jain on today. He discussed his plans for the moon, and mentioned his company became the first private one to get fully licenced to land a space craft on the moon. Pretty cool stuff.
I'm continually amazed at the speed in which you crank out new content...the amount of detail...and your breath of knowledge on the subject matter. Makes me wonder if I could sufficiently explain the use of a toilet paper roll to the sophisticated audience you have developed and their expectations of your content. You have set the bar high. Well done.
Just a brief historical point, the single-skip reentry profile WAS (partially) used once, by Apollo 11, due to a storm front moving in on the original recovery zone. The spacecraft did not fully skip out, but it did get a little extra range during the "up-control" period.
Correct me if I'm wrong but my understanding was that Apollo's use of a lifting reentry upon return from the Moon was required in order to be survivable; a ballistic reentry at translunar velocity would either destroy the heat shield and/or kill the crew by excessive Gs. For a LEO mission, ballistic reentry was a fallback option, say, from a Skylab mission.
Hi Scott, have you thought about doing a higher maths video for the older kerbonauts among us? Being able to relate calculus, differential equations, and linear algebra to KSP would inspire a lot of kids to pay attention in maths!
I'd love to see a video explaining the bizarre aerodynamics of the reverse shuttlecock shape. I saw another video of someone shooting this shape out of a gun and it was in fact stable. But it seems counter intuitive somehow and I'd love to see an explanation for why it is. In the video of the guy shooting this shape he was also surprised and tried shooting the shape out in the more intuitive pointy end first. That turned out to be unstable and it tumbled. Fascinating but I don't understand why it works as it does.
Center of gravity, it's the same reason that when you throw a dart backwards it turns around in flight and sticks in the dartboard as if you threw it normally. And with bullets it's because the center of gravity is more towards the rear of the bullet that rifles have rifling, by spinning the bullet it stabilizes and doesn't tumble end over end from trying to turn itself around in flight due to the CG being towards the rear. The longer a bullet is compared to it's width the faster it must be spun to stabilize it, the first rifled guns were firing balls, they have rifling that only makes one twist in around 30 inches or so because the projectile is as wide as it is long so it only takes a small amount of spin to stabilize it, modern rifles that shoot bullets that are much longer then they are wide have a much faster twist in the rifling, usually around one twist in 12 inches. Nowadays barrel makers are making barrels with much faster twists for long range shooters, heavier bullets are best for distance shooting, making a heavier bullet to fire out of the same gun means you have to make it longer to add weight since you can't make it wider, years ago before these faster twist barrels were being made long distance shooters wouldn't even bother checking their grouping at 100 yards when testing different loads because the bullets weren't stabilized yet at that short of a distance and they would "key hole" through a paper target nailed to plywood because they would up-end and pass sideways through the target after the nose of the bullet hits the target because of the wobble they still had from not being fully stabilized yet, back then most distance shooters wouldn't even bother testing unless they had access to a shooting range of at least 300 yards. Years ago a ballistician that designed heavy artillery guns theorized that when the projectiles came out of one of those big guns they wobbled at the beginning of their 10 mile journey, everyone else in the business dismissed his theory until the 1920's and the advent of high speed film that could be slowed, turns out he was right.
I guess that explains why you can hear Alan Shepard's voice shaking during re-entry - the Mercury sub-orbital descent was apparently a rougher ballistic-style ride.
4:58 As I recall, the main reason why Apollo flew an aerodynamic re-entry (with an offset centre of mass) was it gave them a wider range of incoming angles, and hence a wider safety margin. Otherwise the tolerance on the re-entry angle would have been very tight, and the risk of missing it (with consequent loss of the astronauts) too high.
I emulated this in the past by positioning about .5t of mass off-center from the capsule, but this cfg trick is an even better option. BTW, I HIGHLY recommend the Command Module episode of the "Moon Machines" documentary series for even more detail about how the CM navigated to its target landing zone while flying through the atmosphere.
*shrug* I mean the stock game is set up the way it is to make things easy for people who don't understand these things to get their feet wet. This kind of extra realism is the realm of mods in my opinion. As long as they keep their game mod-friendly and easy to mod, and I can create my super-realistic space program sim, then I am happy
Scott - When you talk about g-forces are you including roll as well as decel? Can you tell me what a typical roll rate might be and what limits shouldn't be exceeded to keep the crew from being incapacitated? Love your videos!!!
Even more horrifying than a suborbital descent would be falling off a space elevator from a few 1000km up. From such an altitude the horizontal velocity would still be negligible but gravity is still nearly 1gee and there is plenty of time to accelerate, the elevator capsule would hit the atmosphere going at like 4000m/s, as it descends to about 50km the air gets thick enough to cause substantial drag and over the course of about 5s it comes to a screeching halt, exposing passengers to a max of about 60gees. If you fell of a space elevator from high up you stay in orbit or graze the atmosphere, if you fall off from under a few hundred km you can land on parachutes. From intermediate altitudes, you become jam regardless of the ability of how tough the capsule is.
Scott, speaking of controlled semi-ballistic reentry, and CoM offsets, could you speak about the little weights added on the sides of some Mars rover heatshileds ? They were dropped just before opening the supersonic chute if I remember correctly =)
I accidentally have an offset CoM on some escape pods for an LKO rescue station. Actually worked out pretty good for steering since, just like the real thing, there's only enough power for rolling. Not so good for the deorbiting burn though.
Scott, Speaking of ways to get back down... This might be before your time but you might be interested in the "Rotary Rocket" company. Their plan was to cross a helicopter with a rocket thus fusing the two most dangerous flying machines into a single awe inspiring death trap. Re-entry was to use the helicopter blades to slow re-entry, much like a badminton birdie, following by "controlled" flight. I would LOVE to see an KSP version of the original Roton rocket. Especially the spinning annular aerospike engine. It put the combustion chambers at the end of a set of spokes then spun the hell out of the engine so as to use centrifugal effects instead of a turbopump to provide fuel pressure . More info: en.wikipedia.org/wiki/Rotary_Rocket
Yep I covered this a while back in my series 'Real World Kerbal Space Program' ua-cam.com/video/S9LNAGq1TCM/v-deo.html And then I tried to replicate the landing mechanic in KSP ua-cam.com/video/2f7mvtS7NOM/v-deo.html
So basically what I got was this. The vessel has the same amount of drag and the same densities of atmosphere no matter if it's from orbit or a abort type scenario, but before the orbit reentry has a higher speed it takes longer to slow and thus you see less g forces applied?
Mr. Manley: I am a big fan. Please keep going with your excellent work! May I please make a suggestion? This Ballistic Reentry vs Aerodynamic Reentry vid may have benefited with a quick graph/math? For those who do not want to see the Cartesian graph/calculus, nothing lost. For me, I would learn more about the application of the math to the relevant "rocket science". P.S. I studied some physics as an undergrad.
Looks like it wouldn't take much to skip off into the void of deep space. The big question would be, "Does the craft gain or lose momentum when it does bounce off into space".
You should simulate Starliner re-entering after a completely failed orbital insertion. Would be interesting to see what sort of G loading would occur if Atlas V was all the propulsion they received
Anyone else trying to tell if Bill and Bob look more worried during the faster descent? Serious question: what is the difference in heating of the ship between the different descents ?
Hey Scott, great video. I'm a mechanical engineering student and very interested in spacecraft and was wondering if you could recommend any professional books about spacecraft design/ construction/ systems ? Thanks a lot.
Been playing recently with reentry gliders to do tourist quests, using lift to slow my decent as the crew cabins are unwieldy for reentries that are capsule-like until I get the 2.5 parts.
Very interesting video. Thank you. Please post (or commenters supply) information on how the Apollo CM attitude was controlled during the re-entry atmospheric descent phase. This is the first time I ever heard of it and am most interested-I always thought that the point/timing/attitude of the retro burn at given orbital height was the last time a “control input” could be made and after that, you were just along for the ride. Looking forward to any inputs, Thanks In Advance.
not only does the Gs after the abort get higher than normal entry, but the abort itself has a MUCH higher G force acting on it, as the crew module needs to separate from the bomb underneath as quick as it can. I think some things are like 10 Gs from the abort, on top of the Gs from the booster(s).
Scott, I think Apollo 8 did use that re-entry profile or one similar to it. Just finished up the book "Apollo 8: The Thrilling Story of the First Mission to the Moon" by Jeffrey Kluger and it was discussed there!
Well explained as always. Enjoy when you use KSP to demonstrate real world physics and recreate actual events. Would be interested in seeing a video ( assuming you haven't already done one and I missed it) about the danger of skipping off the Atmos like they talk about in Apollo 13. Was playing KSP yesterday and for the first time I think my Velocity was to high during reentry (3400 m/s) or my AoA was to low during renty and I initially rapidly lost altitude and speed but then before I could shed enough speed to bring Pe all the way down to the ground I started to rise again. Lucky in KSP it just put me round Kerbin again for another go at reentry at a slower Velocity but I know in real life there was a danger if you did not hit the "corridor" of skipping off the atmos and into deep space (not into orbit around the Earth) or burning up if you came in to fast and steep. Would love to see a video on that and maybe a demonstration in KSP. Appreciate yea Scott and love the channel. Be Well.
I don't think skipping off the atmosphere has any danger in terms of flying off in to deep space due to the amount of velocity you need to do that. The danger lies in that their next orbit would be completely uncontrolled without any thrusters, so no fine tuning of their next landing approach or landing position. Because they had no control, their next re-entry might be too steep or too shallow again causing them to burn up or skip off again. Taking this is to account, the amount of time spent in space was longer than they had accounted for, with supplies running low, the astronauts wouldn't survive.
There is absolutely no danger of skipping off the atmosphere and going into deep space, it would be like saying that if a ball fell from a table it might rebound and hit the ceiling. What is dangerous tho is that it makes planning your landing zone quite difficult and you might end up landing on a unwelcoming surface
Upon further research this does seem correct. found a good article on it buy ESA if anyone might be interested. They even example a quote from the movie Apollo 13 and point out that it is flawed in it logic “Listen, listen, listen! They gave us too much Delta V, had us burn too long. At this rate, we’re gonna skip right off of the atmosphere, and we’re never gonna get back!”- Jack Swigert (Character) Apollo 13, the movie. Here is a quote from said article that corroborates what happened to me in KSP. Another example of KSP imitating real life. "If the entry angle is much too shallow, the spacecraft will not ‘bounce off the atmosphere like a flat stone skipping off the water surface of a pond’. A spacecraft generates little or no lift, and the outer reaches of the atmosphere are very tenuous. What will happen is that the spacecraft does enter the atmosphere at orbital velocity, but because it does not enter the denser atmosphere layers, it will not undergo much braking. It will therefore not lose enough of its velocity, and then it will simply continue on its orbit. As this orbit is slightly elliptical, the spacecraft will start gaining altitude again, go out into space and then re-enter the atmosphere after an hour (or more), as its trajectory again leads down - but then it will be at a completely different location than planned and its second entry will certainly no longer be within the ‘corridor’!" - blogs.esa.int/rocketscience/2015/02/05/the-facts-on-reentry-accurate-navigation-is-everything/
Watching Apollo 13 and other movies and even docs about the Apollo program they always seem to make it seem like if they were to miss the corridor that they would burn up or be lost in space forever. I guess that is why I was lead to believe that was the case and I didnt do my own homework. It does make sense though that unless somehow they entered too shallow and came out the other side at a speed greater than the escape Velocity of Earth that they would just continue to orbit and eventually reenter the atmosphere again but in an unpredictable way.
In Apollo 13, they needed to hit the atmosphere and land first try because otherwise the air in the capsule would of killed them before a second pass around Earth could be completed. I believe it is high CO2, not low oxygen which was what caused the air to turn bad
Nice, nice channel. Every time is very interesting theme of the video. Questions I ask myself. Nothing like this in my native language, and in English, too, have not seen anything.
Got a question. Does the atmosphere move with our surface or is it an independent movement? Like if this one spot on earth has a storm and that storm doesn’t move, would the rotation of the earth affect the storm at all?
When it comes to large storm systems such as hurricanes/typhoons the Earths spin is responsible for their general direction of travel. ( Or more so where they can't travel ) So yes the rotation plays a significant factor into weather systems. The atmosphere as a whole moves with the Earth. But within that whole you have sub-systems that behave in according to thermodynamics.
Scott, I don't know if you have done one already but what would happen to an Apollo capsule travelling at 25,000 mph if it had a shallow entry and skipped off the atmosphere. We are always told that was it but I presume a number of oval orbits, skimming the atmosphere. Can you show what would actually happen. Cheers.
I've gotten into trouble in the early game in KSP with ballistic re-entries - not getting enough horizontal velocity to allow sufficient time and angle to decelerate in the atmosphere. Jeb has suffered more than one fiery crash from that.
Hi Scott! This video reminded me of an early set of scenes in First Man. What was depicted was Neil Armstrong "skipping" or "bouncing" the X-15 so it ended up going, unpowered, to higher altitude. The film definitely cast the managers of the program as considering it to be a goof on Armstrong's part. I know the film plays very fast and loose with history, but this is an incident I wondered about. May, possibly, be worth coverage in one of your videos, especially with the film having made the topic current. Thanks!
I remember wondering how, with a shallow aerobrake, a capsule could skip back out into space. Could you run this, Scott, from LEO and jump back into a suborbit?
So, in a ballistic reentry profile, it would be impossible to skip off of the atmosphere, right? All that would/could happen is that you dont slow down fast enough before you leave the atmosphere again?
Well they designed it to look like a tear drop because water always turns into a tear drop because of the aerodynamic forces push it that way. So if u design a tear drop looking space craft of course your going to get a perfect aero dynamic plane
No, that's a myth. A small raindrop will be roughly spherical. A large one will get flattened at the bottom due to air resistance. If it gets too big it fragments into smaller (near-spherical) raindrops. [ pmm.nasa.gov/education/articles/shape-of-a-raindrop ]
You use a falling space pod in kerbal space program but I use a supersonic plane catching device to catch falling space pods no need for long wait of falling
Hey Scott, how about an "Armageddon challange" in KSP? Try to land a Space Shuttle type Orbiter on an Asteroid, which is on collision course with Kerbin, and redirect it around Kerbin.
So technically it's always aerodynamic, but the name changes to "ballistic" when you don't use the aerodynamic effects to control the descent trajectory?
Well looking at the accelerometer, it seems that the astronauts were not killed by re entry but by the parachute opening
Col. John Stapp proved it's not how much deceleration you encounter, but how long it lasts. A few seconds at 12g might be bad, but a lot better than sustained 4g.
so long as it doesn't snap your neck. hitting concrete after falling off a ladder will give you a few milliseconds of 50g.
0.0000001 seconds of 200gs is probably worse than an hour of 4 gs
Squad is refusing to implement RealChute for years, it's so annoying.
Pluto :
nope, it is not. 200g for 0.0000001 is 2*10^-12m so it is not possible to notice
You've played KSP for 91 days and 5 hours
I have some one on my friends list with around 24k+ hours on gmod. That is almost 3 years or 1095 days
Phone he could of had it open for most of the time he wasn't playing ... which iiiss kinda cheating about the time
@@Tagson He owns a server, and his GF also playes on the same account and they take turns moderating.
@@Tagson anyways, you could say the same for scott, as he idles out all of the space traveling.
The real question is: could we use Kerbal Space Program to solve concrete problems in AI?
1:11 - Also, real spacecraft usually don't wait _quite_ that long to deploy their parachutes.
Sean McDonough you can adjust to however you want mid flight in game
Apparently Apollo 11 did use the reentry skip manoeuvre to avoid a thunderstorm.
i could be wrong but i believe Apollo 8 did as well.
Ballistic Reentry: It's falling with style.
And of course when he opened the parachutes it maxed out at 12 Gs
yeah KSPs parachute simulation leaves much to be desired.... that's why RealChute is great!
not sure how, if I try the same thing my parachute rips off, I have to arm them much higher up so they open early and slow me down before opening fully.
you're not using any mods?
its been a while, so I went and tried it, and it didnt rip off, but it smashed me right into the ground for waiting that long. no mods. vanilla only.
Momentary Gs can go to 14 before death.
Although I do really enjoy the science videos, a KSP video is welcome surprise too
it's a KSP video explaining the science of a rocket failure thing. best of both worlds, no?
regardless of the fact that KSP is mostly unexplained rocket failures ;)
forgetting the fact that this channel was mostly forged around ksp
This one isn't exactly as much rocket science as flight science.
A surprise, to be sure, but a welcome one.
Thank you for the video.
I was one of those who asked what a ballistic re-entry meant.
This video really helps me - I still don't fully understand what is happening but now you have shown me in an animation what happens I can replay it in my mind until I understand what is happening.
Based on what you have shown it sounds like one of the main factors is the altitude, since the re-entry vehicle is moving at a high speed in a still relatively high density atmosphere the deceleration(acceleration really) is higher than if it was re-entering the atmosphere from 'space' where it can decelerate at a slower rate due to the atmosphere being less dense.
sort of got it. What ballistic re-entry means is that the capsule is not doing any maneuvering to try and control it's decent, instead it "flies as it flies", it is un-controlled (which sounds scary hence why they say ballistic trajectory or ballistic decent), doesn't matter what altitude it is descending from.
What Scott is showing us is WHY you would want a capsule to normally control it's decent (because it can reduce g-loading), he is also showing what can happen if the capsule tries to control it's decent improperly (the super fast and steep entry that resulted in really high g-loading). He then showed us how a ballistic sub-orbital reentry could be harder on the crew than a nominal re-entry from orbit (this is due to the altitude, as you said, even though returning from orbit means you start off going faster).
This was a very well explained video. I enjoyed being led through with examples and numbers and side-by-sides. Obviously lots of planning went into it.
Likewise. I had no idea about the deliberate centre of gravity offset to generate uplift. Kewl!
wow how long has it been since he's used the ukulele intro? I feel like it's been forever since I've seen it.
September 24
@@DanSlotea holy shit really?? Well I missed it lmao
He uses the ukulele intro for his KSP videos, and the other one for his real science ones
When I studied space dynamics as an undergraduate that was one of the concepts that I really found surprising. That you could fly the space capsule into atmosphere.
I believe the details on how soyuz capsule controls roll-pitch-yaw during re-entry (shifted CoM) may confuse those who are unaware of the difference between controlled and ballistic trajectories - the main idea of the vid is right on point: at that alt you do not need to control capsule - so after abort sequence they let it fly as it flies - and call that ballistic trajectory (which actually means 'let it fly as it flies')
It kinda makes sense. I imagine the astronauts when thinking about performing the ballistic reentry "Huh... we just had an abort due to a booster failiure... let's just keep this thing doing what it has to do, better if we don't try space cowboy with it".
"you do not need to control capsule" Well you have to spin it. Not sure if you missed that or if you're trying to simplify.
@@ewthmatth you do not... Once it sits in air flow stream its shape does it. There is no control. Again, at higher altitude you can control it, at altitude/speed they've aborted there is no such possibility. It's not a choice its posr-factum name for 'letting it fly as it flies'.
I'd love to see a video discussing Max Q and how to deal with! Keep up the good work Scott!
Your ability to explain this stuff in understandable ways is commendable. Keep up the awesome work!
Brilliant. Seriously. Never seen this explained so thoroughly and at a level I could grasp.
Hi Scott,
Another great presentation as always.
Back on April 19, 2008, So-yeon Yi, Peggy Whitson and Yuri Malenchenko, aboard Soyuz TMA-11, are said to have suffered through up to 10 G’s during a ballistic re-entry. Whitson said "I saw 8.2 G's on the meter and it was pretty, pretty dramatic," Also the ballistic re-entry caused them to land about 260 miles short of the targeted landing site.
Regards,
Tom Charlton
They came from orbit. MS-10 was a launch abort
Want to decrease drag, increase lift? I have this new aerodynamic engineer's trick called a change of reference axes!
I'm at a loss, how is an ax going to help?
Explain please.
@@lordgarion514 axe makes you smell better
@@confuded I think they mean that if a craft is super draggy you can just consider it "lift," just in the backwards direction.
I think they mean that if a craft is super draggy you can just consider it "lift," just in the backwards direction.
Thanks for the demonstration. I wasn’t clear on the difference so this really helps. Cheers.
Can't get enough! I love these videos explaining the launch failure. It is not a good thing this happened, but the silver lining is the education of how things work on such a failure. And, of course, the education part of, "Space is NOT a nice place, and getting out there is REALLY freakin' HARD!"
I always put a service module(the one with the door) under the command module with science stuff and extra rcs fuel then the heat shield and I offset the center of mass with how I arrange everything, and I also use 2 small side parachute offset to the side so In case I have a heavy load, like full science equipment and extra rcs, the Impact will be on a corner and allow the craft to roll out extra speed. I have been using this design for as long as I remember the service module being in the game and it never failed me, even reentering from a free return from minmus with steep entry
İ just completet my first mun mission and then i was going back to kerbin but during the reentry i realised i forgot the parachutes on the lander! But my professional piloting skils and the landing asist engines on the lander saved 2 kerbals in that day. ( sory for my bad english im Martian )
NEXT: DUNA lander without parachutes :)
I could understand this. After all, you guys don't use parachutes on Mars.
I did something similar thought about leaving them in orbit and sending up a rescue mission but noticed I had a stage with a 1/3 tank of propellant and a thrust greater than 1 to 1 so I decided to come in with the stage still attached and try to land with it.
I cannot seem to effectively control rockets via keyboard so all of my reentry is done with a launch vehicle that took off from a runway.
Forgetting parachutes, we’ve all been there my young grasshopper
I already knew the difference but it's wonderful to see you explaining it so clearly, it makes other people know it very well and that's really great.
holy shit Scott actually maneuvered the damn thing toward the runway
Will you do a video on the differences between ablative materials for reentry as opposed to ceramic thermal tiles and how each one is best suited for what kind of vehicle is used to reenter the atmosphere? That would be interesting, at least in my opinion lol. Bill & Bob Kerman both want to see it as well...so thats always nice. 😁
It would be.... now I need to do research.
so this is where the heat shields video was born
I'm not a big fan of KSP videos, but you somehow managed to keep my attention till the end of video :) Good job!
Just when I'm about to go to sleep. Thanks scott
Great stuff!
Not sure if anyone here watches the Mind & Machine channel but they had Naveen Jain on today. He discussed his plans for the moon, and mentioned his company became the first private one to get fully licenced to land a space craft on the moon. Pretty cool stuff.
Fantastic explanation. Using ksp to show what's going on was super helpful.
I'm continually amazed at the speed in which you crank out new content...the amount of detail...and your breath of knowledge on the subject matter. Makes me wonder if I could sufficiently explain the use of a toilet paper roll to the sophisticated audience you have developed and their expectations of your content. You have set the bar high. Well done.
6:10 that flip from nose-first to tail-first has got to be brutal on the crew.
What a fountain of knowledge you are Scotty
Just a brief historical point, the single-skip reentry profile WAS (partially) used once, by Apollo 11, due to a storm front moving in on the original recovery zone. The spacecraft did not fully skip out, but it did get a little extra range during the "up-control" period.
Great explanation, I thought in The Right Stuff the overdid the reentry of the suborbital flights but now it makes sense.
Correct me if I'm wrong but my understanding was that Apollo's use of a lifting reentry upon return from the Moon was required in order to be survivable; a ballistic reentry at translunar velocity would either destroy the heat shield and/or kill the crew by excessive Gs. For a LEO mission, ballistic reentry was a fallback option, say, from a Skylab mission.
Hey Scott! I think you’d love this game called Space Simulator. It does simulate aerodynamic reentries and I think you’d like it.
I already played it on NASA’s twitch stream. Its’s not as good as simple rockets.
Oops. Nice video though, you did a great job explaining it :)
Hi Scott, have you thought about doing a higher maths video for the older kerbonauts among us? Being able to relate calculus, differential equations, and linear algebra to KSP would inspire a lot of kids to pay attention in maths!
I'd love to see a video explaining the bizarre aerodynamics of the reverse shuttlecock shape. I saw another video of someone shooting this shape out of a gun and it was in fact stable. But it seems counter intuitive somehow and I'd love to see an explanation for why it is. In the video of the guy shooting this shape he was also surprised and tried shooting the shape out in the more intuitive pointy end first. That turned out to be unstable and it tumbled. Fascinating but I don't understand why it works as it does.
Center of gravity, it's the same reason that when you throw a dart backwards it turns around in flight and sticks in the dartboard as if you threw it normally.
And with bullets it's because the center of gravity is more towards the rear of the bullet that rifles have rifling, by spinning the bullet it stabilizes and doesn't tumble end over end from trying to turn itself around in flight due to the CG being towards the rear.
The longer a bullet is compared to it's width the faster it must be spun to stabilize it, the first rifled guns were firing balls, they have rifling that only makes one twist in around 30 inches or so because the projectile is as wide as it is long so it only takes a small amount of spin to stabilize it, modern rifles that shoot bullets that are much longer then they are wide have a much faster twist in the rifling, usually around one twist in 12 inches.
Nowadays barrel makers are making barrels with much faster twists for long range shooters, heavier bullets are best for distance shooting, making a heavier bullet to fire out of the same gun means you have to make it longer to add weight since you can't make it wider, years ago before these faster twist barrels were being made long distance shooters wouldn't even bother checking their grouping at 100 yards when testing different loads because the bullets weren't stabilized yet at that short of a distance and they would "key hole" through a paper target nailed to plywood because they would up-end and pass sideways through the target after the nose of the bullet hits the target because of the wobble they still had from not being fully stabilized yet, back then most distance shooters wouldn't even bother testing unless they had access to a shooting range of at least 300 yards.
Years ago a ballistician that designed heavy artillery guns theorized that when the projectiles came out of one of those big guns they wobbled at the beginning of their 10 mile journey, everyone else in the business dismissed his theory until the 1920's and the advent of high speed film that could be slowed, turns out he was right.
5:16 - OK. "There's a computer failure."
I guess that explains why you can hear Alan Shepard's voice shaking during re-entry - the Mercury sub-orbital descent was apparently a rougher ballistic-style ride.
I just clicked the like button and it changed from 3K to 3.1K
:O
do it on my channel :D
Mr.Nuclear BG this is a combination of cringe and sad
4:58 As I recall, the main reason why Apollo flew an aerodynamic re-entry (with an offset centre of mass) was it gave them a wider range of incoming angles, and hence a wider safety margin. Otherwise the tolerance on the re-entry angle would have been very tight, and the risk of missing it (with consequent loss of the astronauts) too high.
I believe what doesn't kill you, simply makes your re-entry ballistic.
I emulated this in the past by positioning about .5t of mass off-center from the capsule, but this cfg trick is an even better option.
BTW, I HIGHLY recommend the Command Module episode of the "Moon Machines" documentary series for even more detail about how the CM navigated to its target landing zone while flying through the atmosphere.
Flat bottomed capsules make the rocket world go round.
Your ability to align real nerdery to KSP is astounding.
Brilliant! Love to see same with Mercury Capsule management..rotation alone with center of gravity was controll of shallow or skip.
4G's is not bad. Normal rollercoasters today usually have 4 to 4,5 G for several seconds.
Loved the crew cams!
The devs should add this as a function in the stock game
*shrug* I mean the stock game is set up the way it is to make things easy for people who don't understand these things to get their feet wet. This kind of extra realism is the realm of mods in my opinion. As long as they keep their game mod-friendly and easy to mod, and I can create my super-realistic space program sim, then I am happy
Scott - When you talk about g-forces are you including roll as well as decel? Can you tell me what a typical roll rate might be and what limits shouldn't be exceeded to keep the crew from being incapacitated? Love your videos!!!
The roll rate wouldn't be enough to matter compared to the deceleration forces.
I've always wanted Squad to add in modules with offset CoM, but I've never thought to just do it myself. Thanks for the video!
Even more horrifying than a suborbital descent would be falling off a space elevator from a few 1000km up. From such an altitude the horizontal velocity would still be negligible but gravity is still nearly 1gee and there is plenty of time to accelerate, the elevator capsule would hit the atmosphere going at like 4000m/s, as it descends to about 50km the air gets thick enough to cause substantial drag and over the course of about 5s it comes to a screeching halt, exposing passengers to a max of about 60gees.
If you fell of a space elevator from high up you stay in orbit or graze the atmosphere, if you fall off from under a few hundred km you can land on parachutes. From intermediate altitudes, you become jam regardless of the ability of how tough the capsule is.
Another gem of wisdom passed on - thanks.
Have you discussed lofted trajectories and why they are not desirable for manned flights???
I would really prefer if there is a way out there to completely slow down the re-entry!!!
Well put. That certainly clarifies things.
Scott, speaking of controlled semi-ballistic reentry, and CoM offsets, could you speak about the little weights added on the sides of some Mars rover heatshileds ? They were dropped just before opening the supersonic chute if I remember correctly =)
I accidentally have an offset CoM on some escape pods for an LKO rescue station. Actually worked out pretty good for steering since, just like the real thing, there's only enough power for rolling. Not so good for the deorbiting burn though.
Scott,
Speaking of ways to get back down... This might be before your time but you might be interested in the "Rotary Rocket" company.
Their plan was to cross a helicopter with a rocket thus fusing the two most dangerous flying machines into a single awe inspiring death trap. Re-entry was to use the helicopter blades to slow re-entry, much like a badminton birdie, following by "controlled" flight.
I would LOVE to see an KSP version of the original Roton rocket. Especially the spinning annular aerospike engine. It put the combustion chambers at the end of a set of spokes then spun the hell out of the engine so as to use centrifugal effects instead of a turbopump to provide fuel pressure . More info:
en.wikipedia.org/wiki/Rotary_Rocket
Yep I covered this a while back in my series 'Real World Kerbal Space Program'
ua-cam.com/video/S9LNAGq1TCM/v-deo.html
And then I tried to replicate the landing mechanic in KSP
ua-cam.com/video/2f7mvtS7NOM/v-deo.html
So basically what I got was this. The vessel has the same amount of drag and the same densities of atmosphere no matter if it's from orbit or a abort type scenario, but before the orbit reentry has a higher speed it takes longer to slow and thus you see less g forces applied?
Well ok this video was freakin AWESOME!
nice to see another KSP video again
Mr. Manley: I am a big fan. Please keep going with your excellent work! May I please make a suggestion? This Ballistic Reentry vs Aerodynamic Reentry vid may have benefited with a quick graph/math? For those who do not want to see the Cartesian graph/calculus, nothing lost. For me, I would learn more about the application of the math to the relevant "rocket science". P.S. I studied some physics as an undergrad.
Finally, the return of the blue intro to mark KSP videos!
Looks like it wouldn't take much to skip off into the void of deep space. The big question would be, "Does the craft gain or lose momentum when it does bounce off into space".
I think you nailed it. Nice video.
Great topics as always Scott!
This makes a lot of sense! Great video!
You should simulate Starliner re-entering after a completely failed orbital insertion. Would be interesting to see what sort of G loading would occur if Atlas V was all the propulsion they received
Thanks for this demonstration. Very cool. :)
Anyone else trying to tell if Bill and Bob look more worried during the faster descent? Serious question: what is the difference in heating of the ship between the different descents ?
Hey Scott, great video.
I'm a mechanical engineering student and very interested in spacecraft and was wondering if you could recommend any professional books about spacecraft design/ construction/ systems ? Thanks a lot.
@john smith I second that, but it has a narrow subject-liquid propellants.
Been playing recently with reentry gliders to do tourist quests, using lift to slow my decent as the crew cabins are unwieldy for reentries that are capsule-like until I get the 2.5 parts.
I'm sorry to be that guy, but it's "descent".
Very interesting video. Thank you. Please post (or commenters supply) information on how the Apollo CM attitude was controlled during the re-entry atmospheric descent phase. This is the first time I ever heard of it and am most interested-I always thought that the point/timing/attitude of the retro burn at given orbital height was the last time a “control input” could be made and after that, you were just along for the ride. Looking forward to any inputs, Thanks In Advance.
1 year late but there's a good video by AIRBOYD called Apollo - Atmospheric Entry Phase. Shots from the video appear several times in this one.
Wow! Great video Scott! Well done. How many G's did the Soyuz experience in the abort re-entry?
not only does the Gs after the abort get higher than normal entry, but the abort itself has a MUCH higher G force acting on it, as the crew module needs to separate from the bomb underneath as quick as it can. I think some things are like 10 Gs from the abort, on top of the Gs from the booster(s).
I will have to start using this knowledge to land on the VAB more often...
Flat bottom? I thought it was a fraction of a sphere...
Correct me.
And tell me the proper word
Flat-ish
I hate the flat earthers
meniscus-ish
You are correct. It wasn't completely flat, it was curved.
Hemisphere?
Wow thanks a lot.
I thought i got the point when i first heard about these two terms but you just prooved me wrong.
Thanks for that
Scott, I think Apollo 8 did use that re-entry profile or one similar to it. Just finished up the book "Apollo 8: The Thrilling Story of the First Mission to the Moon" by Jeffrey Kluger and it was discussed there!
Well explained as always. Enjoy when you use KSP to demonstrate real world physics and recreate actual events. Would be interested in seeing a video ( assuming you haven't already done one and I missed it) about the danger of skipping off the Atmos like they talk about in Apollo 13. Was playing KSP yesterday and for the first time I think my Velocity was to high during reentry (3400 m/s) or my AoA was to low during renty and I initially rapidly lost altitude and speed but then before I could shed enough speed to bring Pe all the way down to the ground I started to rise again. Lucky in KSP it just put me round Kerbin again for another go at reentry at a slower Velocity but I know in real life there was a danger if you did not hit the "corridor" of skipping off the atmos and into deep space (not into orbit around the Earth) or burning up if you came in to fast and steep. Would love to see a video on that and maybe a demonstration in KSP. Appreciate yea Scott and love the channel. Be Well.
I don't think skipping off the atmosphere has any danger in terms of flying off in to deep space due to the amount of velocity you need to do that. The danger lies in that their next orbit would be completely uncontrolled without any thrusters, so no fine tuning of their next landing approach or landing position. Because they had no control, their next re-entry might be too steep or too shallow again causing them to burn up or skip off again. Taking this is to account, the amount of time spent in space was longer than they had accounted for, with supplies running low, the astronauts wouldn't survive.
There is absolutely no danger of skipping off the atmosphere and going into deep space, it would be like saying that if a ball fell from a table it might rebound and hit the ceiling. What is dangerous tho is that it makes planning your landing zone quite difficult and you might end up landing on a unwelcoming surface
Upon further research this does seem correct. found a good article on it buy ESA if anyone might be interested. They even example a quote from the movie Apollo 13 and point out that it is flawed in it logic “Listen, listen, listen! They gave us too much Delta V, had us burn too long. At this rate, we’re gonna skip right off of the atmosphere, and we’re never gonna get back!”- Jack Swigert (Character) Apollo 13, the movie. Here is a quote from said article that corroborates what happened to me in KSP. Another example of KSP imitating real life. "If the entry angle is much too shallow, the spacecraft will not ‘bounce off the atmosphere like a flat stone skipping off the water surface of a pond’. A spacecraft generates little or no lift, and the outer reaches of the atmosphere are very tenuous. What will happen is that the spacecraft does enter the atmosphere at orbital velocity, but because it does not enter the denser atmosphere layers, it will not undergo much braking. It will therefore not lose enough of its velocity, and then it will simply continue on its orbit. As this orbit is slightly elliptical, the spacecraft will start gaining altitude again, go out into space and then re-enter the atmosphere after an hour (or more), as its trajectory again leads down - but then it will be at a completely different location than planned and its second entry will certainly no longer be within the ‘corridor’!" - blogs.esa.int/rocketscience/2015/02/05/the-facts-on-reentry-accurate-navigation-is-everything/
Watching Apollo 13 and other movies and even docs about the Apollo program they always seem to make it seem like if they were to miss the corridor that they would burn up or be lost in space forever. I guess that is why I was lead to believe that was the case and I didnt do my own homework. It does make sense though that unless somehow they entered too shallow and came out the other side at a speed greater than the escape Velocity of Earth that they would just continue to orbit and eventually reenter the atmosphere again but in an unpredictable way.
In Apollo 13, they needed to hit the atmosphere and land first try because otherwise the air in the capsule would of killed them before a second pass around Earth could be completed. I believe it is high CO2, not low oxygen which was what caused the air to turn bad
Informative explanation. Thanks Scott!
Nice, nice channel. Every time is very interesting theme of the video. Questions I ask myself. Nothing like this in my native language, and in English, too, have not seen anything.
Scotte, ee’m oonly seeing this nooow, end mæn, eet’s a kiiler! Thanks!
A "computer game" that can be used for a factual demonstration!
I'm to old for ..gaming.. but this is incredible.
It's a simulator.
No one can be too old for gaming!
Got a question. Does the atmosphere move with our surface or is it an independent movement? Like if this one spot on earth has a storm and that storm doesn’t move, would the rotation of the earth affect the storm at all?
When it comes to large storm systems such as hurricanes/typhoons the Earths spin is responsible for their general direction of travel. ( Or more so where they can't travel ) So yes the rotation plays a significant factor into weather systems. The atmosphere as a whole moves with the Earth. But within that whole you have sub-systems that behave in according to thermodynamics.
Scott, I don't know if you have done one already but what would happen to an Apollo capsule travelling at 25,000 mph if it had a shallow entry and skipped off the atmosphere. We are always told that was it but I presume a number of oval orbits, skimming the atmosphere.
Can you show what would actually happen. Cheers.
I guess it come down to how long the consumables would last.
Should've shown the aerodynamic overlay during those re-entrys
I've gotten into trouble in the early game in KSP with ballistic re-entries - not getting enough horizontal velocity to allow sufficient time and angle to decelerate in the atmosphere. Jeb has suffered more than one fiery crash from that.
Hi Scott!
This video reminded me of an early set of scenes in First Man.
What was depicted was Neil Armstrong "skipping" or "bouncing" the X-15 so it ended up going, unpowered, to higher altitude.
The film definitely cast the managers of the program as considering it to be a goof on Armstrong's part.
I know the film plays very fast and loose with history, but this is an incident I wondered about.
May, possibly, be worth coverage in one of your videos, especially with the film having made the topic current.
Thanks!
I was going to make video on this.
Excellent!
So what is the difference between entry and re-entry Is it just as hot Going to space as it is coming back
I remember wondering how, with a shallow aerobrake, a capsule could skip back out into space. Could you run this, Scott, from LEO and jump back into a suborbit?
So, in a ballistic reentry profile, it would be impossible to skip off of the atmosphere, right? All that would/could happen is that you dont slow down fast enough before you leave the atmosphere again?
I have used that one on rare occasions, mainly if the speed would put too much reentry heat to the craft.
Why was Artemis re-entry path nearly 90 degrees to equator?( South to north)
Yes, this seemed unusual to me as well, anybody help?
Well they designed it to look like a tear drop because water always turns into a tear drop because of the aerodynamic forces push it that way. So if u design a tear drop looking space craft of course your going to get a perfect aero dynamic plane
No, that's a myth. A small raindrop will be roughly spherical. A large one will get flattened at the bottom due to air resistance. If it gets too big it fragments into smaller (near-spherical) raindrops. [ pmm.nasa.gov/education/articles/shape-of-a-raindrop ]
You use a falling space pod in kerbal space program but I use a supersonic plane catching device to catch falling space pods no need for long wait of falling
Hey Scott, how about an "Armageddon challange" in KSP? Try to land a Space Shuttle type Orbiter on an Asteroid, which is on collision course with Kerbin, and redirect it around Kerbin.
So technically it's always aerodynamic, but the name changes to "ballistic" when you don't use the aerodynamic effects to control the descent trajectory?
It has to do with the G's. Ballistic reentries don't angle the craft to generate lift and lower the G load on the passengers.
@@Kumquat_Lord I think the g force is a byproduct of the different re-entry methods not the definition.
Where's Jeb?