If Rockets Were Transparent [video]
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Left to right: Saturn V, Space Shuttle, Falcon 9 Heavy, SLS (still under construction).
2:22, you hear Neil Armstrong say "inboard cutout," that is the center engine shutting off to limit the thrust, and therefore G-forces the astronauts felt. As fuel ran out, the rocket stack would weigh less and so the rocket would push harder. By the time the main engine cutoff, the Saturn V was pulling 4 and a half Gs.
Also, just noticed the SLS keeps its launch escape tower (the big needle on the top of the rocket - see this: https://www.youtube.com/watch?v=AqeJzItldSQ) - this wouldn't happen in a real flight. The flight plan calls for ditching than when it's not longer useful - you can hear the Apollo 11 call saying, "tower jettisoned."
https://www.siriusrocketry.biz/ishop/images/EstesStandardEng...
https://farm8.staticflickr.com/7457/12472921013_aa92200267_k...
StackExchange pictures and discussion: https://space.stackexchange.com/questions/4153/could-3d-prin...
It's a silly thing little, perhaps, but it helped shape my personality.
When I got involved with high power model rocketry I'd been flying little Estes kits for years. I had rudimentary understanding of aerodynamic forces and testing for stability, and had hacked around with flight simulation code cribbed from G. Harry Stine's "Handbook of Model Rocketry". I was young and thought I "knew stuff". Somebody at a high power launch remarked offhandedly about the difference thrust profiles of an end-burner vs. a core-burner. After I digested it I began to reflect on the visceral sense of how little I really knew about rocketry, and the world in general, that I felt.
It was a seemingly simple piece of trivia about a topic that's not particularly important in my day-to-day life. It was, however, one of those deeply humbling "unknown unknown" moments. I've grown to absolutely adore the feeling of learning about new, uncharted depths in my knowledge because it means there's something new to learn about. The lesson about false confidence and humility was also a really good one. I hope it was a lesson that changed me for the better.
When I first got into model rocketry, I was inundated with technical material. NASA had a huge variety of short technical briefs on things like stability, drag coefficients, etc - I think they gave them out for free to anyone who asked - and I had a fair collection. Unfortunately the mathematics in in them was far too much for 8 year old me, and I wasn't really able to use them in earnest for anything. Rocket science - proper science - seemed unapproachably complex.
But a few years later I was given a copy of G Harry Stine's book, and it was like the doors were thrown open. Everything in it was hugely practical! And perfectly readable to 11 year old me. One great big book that said "you can totally do all this, and here's how". I credit the BASIC code in the appendices with helping get me into programming. I spent a long time painstakingly translating one of them into TI-83+ BASIC.
So the lesson that I learned was the opposite as yours - it's easier than it looks!
It sounds easy, with hindsight, to say "Of course the burn profile of the fuel grain would determine the the thrust curve". The idea of fuel grain burn profile just simply hadn't occurred to me. Sure-- I knew motors had total and specific impulse but, I grew up on Estes motors as "black boxes" and never thought about motor manufacture or that performance could be engineered. I never thought about the motor as anything more than "put an ignition source in, get energy out".
I know I've had a lot more of these moments. This was just a memory evoked by the parent post. I'm having trouble coming up with another of these "deep holes that look shallow, or don't even look like a hole at all" moments immediately to relate a second anecdote.
These shallow-looking deep holes clearly exist in large numbers. By their very nature we can't know how many there are. They're fractal, too. Inside each one are more similarly-appearing (or not appearing) holes to go down.
That idea might trouble some people, but it's very exciting to me. The only troubling bit is knowing I have a finite period explore the space of knowledge and a limited capacity to understand. That doesn't discourage me, though.
Coming from model rocketry myself, I had the same question, so I went straight to wikipedia to find out: https://en.wikipedia.org/wiki/Solid-propellant_rocket
Somehow I thought that the combustion of the propellant had to be inline with the thrust, but TIL there is a combustion chamber, and it's the ejection of the combusted gases through the nozzle causes the thrust.
I like hearing other people's experience with model rocketry. It's interesting because I experienced it more as model building (assembling and decorating) with a fun day of launching and running after them. I never got into the physics of the flights (other than lighter==higher) or even thought of investigating propellant properties--geometry and chemistry--as amateur rocketry does. I guess nobody told me "you can make your own engines if you want," but even then I'm not sure I would've pursued it.
The thinking at the time was that, without the capsule attached, the tower might not fly as planned. It could be unstable in the thin up atmosphere. It might spin. That lateral thrust, withough the mass of the capsule, might cause it to spiral, leaving it floating out in front of the accelerating rocket.
This became a factor during the (unmanned) Mercury-Restone 1 incident, where the launch tower flew off when the rocket was still on the launchpad, leaving the capsule behind on the rocket because the capsule was only designed to detach when the rocket was in freefall (it wasn't in freefall, because it was still on the launchpad.)
The acceleration of the launch abort system on its own, when it's not dragging the entire capsule with it, is double digit gees. The main rocket is not going to catch up to it and run into it.
Related-ish: https://www.discovermagazine.com/environment/in-russias-spac... (again, most rocket propellants aren't exactly great for you).
Reminds me of the book "Uncle Tungsten", which I highly recommend.
Virgin isn’t trying to leave orbit, but it’s still really an interesting comparison to rockets.
It isn't even trying to reach orbit. As soon as the fuel is exhausted it cannot help but fall back to Earth because it hasn't achieved orbital velocity. The passengers get a few minutes at high altitude, enough to experience weightlessness and see the stars.
It's a suborbital lob, a much more polished version of the X-15 in the 1960s.
[Edit - clarity]
You're right, Virgin's plane gets very high, about one quarter as high as the international space station. But some missions require actual orbit.
The military wanted to launch it in a polar orbit, gather intelligence, and then land back where it started in a single orbit, which moves 2000 km east of where it was at launch.
Edit: glide slope is the word I was looking for.
To match the descent rate and drag profile of the real Shuttle at 37,000 feet (11,300 m), the main landing gear of the C-11A was lowered (the nose gear stayed retracted due to wind load constraints) and engine thrust was reversed. Its flaps could deflect upwards to decrease lift as well as downwards to increase lift.
https://en.wikipedia.org/wiki/Space_Shuttle
https://www.theatlantic.com/photo/2011/07/the-history-of-the...
But I also have to admit I cannot fathom how someone could have not heard of the space shuttle? It was only retired in 2011?
I'm sure there are teenagers out there who are discovering the shuttle just now. This thread might have been started by one.
If, as your tone implies, you believe that every teenager knows everything and it's not possible for some of them to have not heard or these things, then you must in fact be a teenager yourself.
Challenger was mentioned, but only because I brought in a newspaper clipping for the 20th anniversary.
Prepare to be disillusioned about humanity.
Yes the space shuttle was designed to be partially re-usable. The "plane" bit would come back down to Earth and land on a (very long) runway https://www.youtube.com/watch?v=YOxZsbyjSb8
Or the One-China policy.[1]
Or that the United States doesn't have a prime minister. Ever told someone you're from the US and been asked who your PM is? They're not referring to your project manager.
Or that they might actually be the Virgin Islands' president without realizing it.[2]
Or any of the following websites, which are among the top 10 most visited websites according to Alexa:[3]
3. Tmall
5. QQ
6. Baidu
7. Sohu
8. Tmall login
9. Taobao
10: 360.cn
In this case, it sounds like the person who made the comment knew of the space shuttle; they just didn't know much about it or recognize it by name. I bet many readers here could say the same for many of the aforementioned items.
Yet if you went to China and asked about Tmall, I bet you'd get some funny looks. I don't really know for sure, though; I'd never heard of it until today. Sure, I know of Taobao, and I could've guessed that the T in Tmall stood for either Tencent or Taobao, but heck if I know what they do. I misspelled it as `Tmail` initially and only realized my mistake after Googling it.
[0]: https://en.wikipedia.org/wiki/Yuri_Gagarin
[1]: https://en.wikipedia.org/wiki/One-China_policy
[2]: https://www.snopes.com/fact-check/trump-president-virgin-isl...
My four year old plays almost daily with his model of Atlantis. Both his older sister saw Atlantis at the KSP museum after watching a Falcon 9 launch.
There's a few things that led to this. Culturally, the American space program has tended more towards the ideal of the "hero" astronaut than others, and there's been some tension between the technical/automated approach and the pilot-astronaut approach to things. I see this as an extension of that. They even considered having pilots manually control the pitch, etc. of the rockets on their way to orbit with the pilots hand on a joystick just following a "recommended" course to orbit.
NASA had explored various ideas for very precise landings, believing that to be useful especially for rapidly-reusable aircraft. There was very serious consideration to having Gemini capsules land with a glider and the astronauts facing forward similar to an aircraft: https://en.wikipedia.org/wiki/Advanced_Gemini#Gemini_Paragli....
And for as expensive as Shuttle was, it had a pretty powerful capacity that mostly made up for it... look at the cost per kg of payload on Commercial Resupply Services to ISS and the cost per seat of Commercial Crew. Shuttle could do about 10 tons of pressurized cargo and 6 (and sometimes even 8) crew, plus about that much down-mass capability, & another robotic arm and airlock. The cost to replicate that capability 1-to-1 is about the same... Of course, that level of capability wasn’t needed as much after ISS was built, and Shuttle couldn’t stay on-orbit for longer than a couple weeks or so. And most importantly, Shuttle was stuck in LEO and could never venture farther and lacked safety features like a launch abort system and was too expensive and unsafe to justify for standard commercial launches in the 21st century.
Not bad for tech developed in the 1970s, tho. The only individual spacecraft (besides Buran) that is comparable in scope and ambition and flexibility is SpaceX’s Starship.
The Shuttle was one of the most expensive ways of getting to Space BY FAR. As every flight had to be a human flight.
Having a vehicle that could do everything, even when 90%+ of the mission only required a small part of the capabilities made it untenable.
With one simple Dragon like capsule you can replicate both crew and cargo up and down transportation for most of the things you need. If you need to transport big pieces, you can just put them on top of a rocket by itself as most station outside of part of the ISS were built.
The way the Russian designed the Buran and Energia system was far more capable of doing all those things. This was mostly because most in the Russian space flight program thought that Shuttle was a terrible idea and they didn't want to handy cap their next generation rocket to a Orbiter.
Had the Soviets not collapsed, their launch capability would have outstripped the US by 4x.
> Of course, that level of capability wasn’t needed as much after ISS was built
It wasn't needed to build the ISS in the first place. Its rather that the ISS was designed TO REQUIRE the Shuttle.
It would have been far cheaper to use the cheapest commercial rockets and the Ariane to build ISS.
> Not bad for tech developed in the 1970s, tho.
A lot of the technology was great, but great technology doesn't make a great product.
They payed almost 90M per seat for Soyuz at least in the last couple.
In comparison, the program cost of Shuttle per flight was 1.5 billion per flight. They would almost never fly more then 4 people on those flights (just as Dragon can also take 7 people, but NASA only takes 4). And the Shuttle was not getting cheaper and the flight rate was not getting faster.
NASA of course has 2 contractors the other was 4.2 billion and the per seat cost is somewhat higher, not sure exactly with the numbers, like 70M or so.
What the per seat cost overall cost are we will see over time. After the initial maximum flight Commercial Crew contracts run out, NASA can renegotiate after that initial contract and likely get a lower per seat price then.
We will see what the end-to-end lifetime per seat cost are for NASA.
I can't give you perfect numbers for perfect Cargo without a lot of research. It depends if we are talking CRS1 or CRS2 contract and there are 3 providers that are all somewhat different, different proportions of up-mass, down-mass and other capabilities, some that the Shuttle didn't have.
The Shuttle could theoretically transport a huge amount of unpressurized cargo but if you are not building a Space station its hard to actually utilize that space fully. So an analysis would have to include the actual payload and so on. That is getting to complex here.
What NASA values seems to be having much less risk on one system. Having different vehicles on different rockets and being able to deliver what they want when they want it and get it back when they want it back.
SpaceX's price per seat is $55m, Boeing is $90m, same as Soyuz.
And it's false that "[t]hey would almost never fly more then 4 people on those flights", as you can see from the list of Space Shuttle missions: https://en.wikipedia.org/wiki/List_of_Space_Shuttle_missions (5th column lists number of crew... To ISS it's usually 7 crew but sometimes 6 and only one time 4). The reason why is they could do a "crew surge" where they could get a whole bunch of work done on Station for a couple weeks and then the extra folk would go back down.
And it's false that Dragon can now take 7 people... They switched to 4 because of the need to change the orientation of the seats to ensure safe splashdown and the 7 seat configuration no longer fit. There were some configurations of Shuttle that would've allowed like 74 additional passengers, too, with a passenger module, but they never flew that variant either.
So again, 7 seats at Boeing's $90 million would give an additional $560 million per mission (or $385m for SpaceX), for a total of $1.1 billion (or $845m), not counting the capaiblity of the extra airlock or the extra robotic arm for servicing capability, plus the ability to take up full ISPR racks or return large pieces of external cargo or...
...So again, even with the $1.5B figure (which includes a ton of overhead at KSC and JSC and elsewhere that would probably have to be covered in some other way), it's still pretty competitive with commercial crew. And that's not counting the NASA side of the commercial crew program, which is substantial.
So I'm with you on commercial crew and cargo being good. I think two or more providers is a more robust system, and I agree it would've been possible to build a big space station without Shuttle (the Russians did it). But the more you dig in to Shuttle's capabilities, the more expensive it looks to replicate. Shuttle really wasn't that bad considering how compromised the design was by zipcode engineering and inability to effectively cost share with commercial or military stuff (later on) and being essentially a traditional government contractor run system.
...the all-in price per launch of Shuttle may have been about $1.5billion, but the marginal price was around $500 million. If they had ever used that 74 passenger module (plus 6-9 crew), that would've been a marginal price per seat of just $6 million... Not too bad, really.
But it was never cheap enough or robust enough to launch often enough to ensure safety without launch abort. Hopefully Starship will change that, enabling a marginal price per seat of something like $100,000 for a trip to orbit...
Thinking back, I was quite fascinated by rackets and only when I was 7-8 did I get across a book on rockets with very colorful fold out posters in it. I think it’s great to have all this educative material on youtube, I will curate some cool playlists for him to watch and learn things.
Why is a car housed atop the third rocket? You can see it around 4 minutes after the housing is jettisoned - https://youtu.be/su9EVeHqizY?t=239
(I was just about to post this question when I decided to just look it up - I vaguely remember hearing something about this - https://en.wikipedia.org/wiki/Elon_Musk%27s_Tesla_Roadster )
But its defiantly just because of his ego, not thought went into it beyond then that.
The really hard part is keeping the explosion intentional and pointed where you want it to go.
One failure mode, out of the many many possible failure modes, that's particularly interesting to me is that if the pressure in the pipes going into the turbopumps (which push the fuel into the combustion chamber fast enough to keep the explosion going) is too low, then you'll get cavitation on the back of the turbopump blades, and the forces from that will destroy the turbopump in under a second. Kaboom.
Oh, also, these pumps have to spin so fast that they themselves are driven by essentially little mini rocket engines.
For a visual depiction of the complexity of rocket engines, check out SpaceX's Raptor engine, arguably the most advanced engine being produced right now: https://imgix.bustle.com/uploads/image/2020/4/6/c1349369-162...
I'm no rocket scientist, though, just an interested amateur. Real rocket scientists please correct me if I got anything wrong!
This is actually not true. These turbopumps are quite large and spin fairly slowly. The design RPM on the F-1 turbopump appears to have been 5500 RPM, for example. (That's not to say they aren't complicated, because they were using 55,000 horsepower to push the propellants into the engine.)
"Question: Are inertial forces required, and incorporated into the designs of rockets, in order to keep liquid fuel at the bottom of each tank?"
Reply: "They are in constant acceleration except when staging or after a shutdown before a re-start. They use ullage motors to accelerate the rocket just enough to settle the fuel (either small solid rockets or reaction thrusters) when they are in zero g."
Reply 2: "Apart from Ullage Motors you can also do "Hot Staging" where you light the next Stage while the current one is still burning. That's why a lot of Russian Rockets don't have this open Interstage Sections where you can see the Engines instead of Interstage Fairings."
I’ve never really understood how solid fuel boosters work. Are they filled with something granular like sand, that empties down the rocket tube?
The video makes it seem as if the entire tube is on fire at the same time.
It’s also fantastic that an asymmetric vehicle like the Space Shuttle was ever built. What an outlier it seems, amongst the more, I suppose traditional looking rocket designs in this video.
A very poetic leap, as well, to think that the same orbiter that climbs under so much power is the same vehicle that glides into land without power, all the way back from orbit!
The way it works, is that it burns from the insight out, like a hollow candle. The trajectory of the booster is basically molded into the hole in the middle. Once you light in on fire, the booster is gone fly its trajectory whatever you do.
Here you can see all that pretty well:
so yeah it is all burning at the same time
In the OP's video, it looks like the fire is magically coming out of thin air... it'd be hard to do the animation style I linked at the distance in OP's video though, so I'm not sure how they could better animate a solid fuel rocket
It’s ironic how much Starship resembles a 1930’s pulp-fiction rocket.
https://en.m.wikipedia.org/wiki/Space_Shuttle_Solid_Rocket_B...
https://www.northropgrumman.com/space/nasas-artemis-program/
I mean intellectually people know that. Rocket = "Engine" + "Fuel tank".
But I still think that when people are imagining the awe-inspiring power of a massive rocket carrying humans into space, they're not dwelling on the fact that the majority is just a big cavernous vessel for fuel.
And by any definition, the Saturn V carried the entire stack into orbit. From orbit you're halfway to anywhere.
If you really to give more (rightfully deserved) credit to the Saturn V, then in fact you can see how much more payload and propellant is on top of the still-firing S-IVB at the end of the video.