Shuttle Booster Video Up- and Reentry- with Sound

[kilemall]

Posting this youtube because I think it gives one heck of a visual and auditory set of occurrences to build into our takeoffs and landings.

https://www.youtube.com/watch?v=2aCOyOvOw5c

I particularly appreciate the transonic vapor and the speed down, then air resistance as the boosters hit their low atmosphere terminal velocity prior to chute deployment.

 

[lostscout5]

Very cool! Thank you for posting that.

 

[kilemall]

Heh, while rewatching that transonic part, a rather jarring thought occurred to me- the speed of sound is going to be different on different worlds even ones with a Nitrogen/Oxygen mix thanks to different percentages, plant oxygenation inputs and gravity.

Mach 1 is going to be a variable, and with it the effectiveness of different aircraft hull designs.

 

[warwizard]

Even on earth the speed of sound varies by altitude.

 

[esampson]

It is very cool, but you should be very careful about looking at it as a reference for Traveller. It probably has about the same relationship to a launch in Traveller as watching a Spanish galleon casting off has to do with a modern ship launching.

Doing some quick math it takes about 40 seconds for the ship to reach 720 miles an hour. This is a bit below 1G of acceleration and it is tempting to assume that since Traveller ships are capable of that level of acceleration and greater they would likewise accelerate at the same rate (or higher). However, the truth of the matter is that they probably wouldn't launch at full acceleration. Our rockets do this because they have very limited fuel. The longer a rocket remains in the atmosphere the more fuel it wastes fighting air resistance so we want them to burn as strong as possible. Ships in Traveller have effectively unlimited fuel, from a launching and landing point of view. This drastically reduces the need for rapid launch to the point that issues such as noise abatement will probably become more important.

The shuttle also rolls. It does this because we don't send rockets straight up. If we did we would have to put enough energy into the rocket to reach escape velocity, otherwise it would fall back to Earth (additionally most of our launches are for things like satellites and we don't want those to be flying away from us forever). So instead we put things into orbit. That requires a lot of lateral motion. We start straight up and transition to an angle of 0 because that is the most fuel efficient launch path (and since we are transitioning from a 90 degree angle to a 0 degree angle we roll the ship so that the centripetal force pushes the astronauts 'down' into their seats).

Engines in Traveller are so efficient, however, that ships probably rarely orbit. Even in the case of large ships which can't land there is rarely a point to having them orbit. Instead they would most likely take up a position above a point on the planet and then remain in the same position relative to the planet (I'm not referring to a geostationary orbit which requires a specific altitude and can only be performed over the equator but an operation where the ship basically is in powered flight around the planet). This would enable the ship to be approximately 1/100th of the distance of a geostationary orbit and would prevent complications of trying to reach the ship when it is on the opposite side of the planet. The one caveat to this is that TNE ships are probably not efficient enough to perform such a maneuver.

 

[kilemall]

I agree and disagree Esampson.

I would agree that the relative capabilities/needs of the two technologies means entirely different flight paths in most cases and that one should not take that video literally as a case of a Traveller launch.

What is interesting to me is the audio, the transonic vapor, how fast the sky went black, how far up sound is still traveling, how quickly components burned even for the few seconds each element of the booster was exposed during the tumble, and a raw reminder of the often overlooked terminal velocity of our ships at low alt.

All little details the astute ref can make use of to make takeoff, reentry and associated hijinx more real.

 

[Spartan159]

Thanks for posting that.

 

[pshrynk]

The shuttle also rolls. It does this because we don't send rockets straight up. If we did we would have to put enough energy into the rocket to reach escape velocity, otherwise it would fall back to Earth (additionally most of our launches are for things like satellites and we don't want those to be flying away from us forever). So instead we put things into orbit. That requires a lot of lateral motion. We start straight up and transition to an angle of 0 because that is the most fuel efficient launch path (and since we are transitioning from a 90 degree angle to a 0 degree angle we roll the ship so that the centripetal force pushes the astronauts 'down' into their seats).

My recall of college physics is that it really doesn't matter what direction you point a rocket except straight down. Once you've achieved an orbital velocity it will orbit. The direction determines the ellipse of the orbit and I can't remember what the effect of straight up acceleration is. However, the Coriolus Effect will drag the craft "eastward", which is why they chose Cape Canaveral for the Kennedy Launch Facility (or whatever they are calling it now.)

 

[aramis]

My recall of college physics is that it really doesn't matter what direction you point a rocket except straight down. Once you've achieved an orbital velocity it will orbit. The direction determines the ellipse of the orbit and I can't remember what the effect of straight up acceleration is. However, the Coriolus Effect will drag the craft "eastward", which is why they chose Cape Canaveral for the Kennedy Launch Facility (or whatever they are calling it now.)

If the total ∆V is sufficient, straight up is the most time efficient escape course. If ∆V is insufficient for breakaway, you come right back down where you left, moved eastward 360°*(Flight time/rotation time)... on earth, each 4 minutes is 1 degree.

If you launch from any point but the equator, the orbit will be inclined; at the equator, anything other than due east or due west results in an inclined orbit.

 

[esampson]

My recall of college physics is that it really doesn't matter what direction you point a rocket except straight down. Once you've achieved an orbital velocity it will orbit. The direction determines the ellipse of the orbit and I can't remember what the effect of straight up acceleration is. However, the Coriolus Effect will drag the craft "eastward", which is why they chose Cape Canaveral for the Kennedy Launch Facility (or whatever they are calling it now.)

Kind of true, but not exactly. Mathematically almost anything other than straight down will result in an orbit around the center of mass as long as you ignore air resistance, it will just be a highly elliptical orbit. However, the two factors of 'around the center of mass' and 'ignoring air resistance' are critically important.

Technically if you threw a baseball it would orbit around the center of mass if you ignore air resistance. The problem is that the highly elliptical around the center of mass intersects the surface of the Earth, which is obviously bad. Even if you were to fire a baseball at a velocity of approximately 27 times the speed of sound (orbital velocity at the surface of the Earth) it wouldn't stay orbiting because the air resistance would slow it down (well, mathematically it would slow it down. It would actually burst into flames and be destroyed) and it would crash back to Earth.

So if you shoot a rocket 'straight up' it will be dragged into a highly elliptical orbit (I'm not sure the Coriolis effect is the correct force, but things such as Earth's own orbit around the Sun will mess up the perfectly 'straight up' angle) but unless you put tremendous amounts of thrust into it that orbit won't be stable as perigee will probably be below the surface of the Earth.

Even if you did put enough energy into the rocket such orbits are of very limited use. We much prefer to use circular orbits.

 

[pshrynk]

Kind of true, but not exactly. Mathematically almost anything other than straight down will result in an orbit around the center of mass as long as you ignore air resistance, it will just be a highly elliptical orbit. However, the two factors of 'around the center of mass' and 'ignoring air resistance' are critically important.

Technically if you threw a baseball it would orbit around the center of mass if you ignore air resistance. The problem is that the highly elliptical around the center of mass intersects the surface of the Earth, which is obviously bad. Even if you were to fire a baseball at a velocity of approximately 27 times the speed of sound (orbital velocity at the surface of the Earth) it wouldn't stay orbiting because the air resistance would slow it down (well, mathematically it would slow it down. It would actually burst into flames and be destroyed) and it would crash back to Earth.

So if you shoot a rocket 'straight up' it will be dragged into a highly elliptical orbit (I'm not sure the Coriolis effect is the correct force, but things such as Earth's own orbit around the Sun will mess up the perfectly 'straight up' angle) but unless you put tremendous amounts of thrust into it that orbit won't be stable as perigee will probably be below the surface of the Earth.

Even if you did put enough energy into the rocket such orbits are of very limited use. We much prefer to use circular orbits.

Oh, what fun is that?

 

[esampson]

I agree and disagree Esampson.

I would agree that the relative capabilities/needs of the two technologies means entirely different flight paths in most cases and that one should not take that video literally as a case of a Traveller launch.

What is interesting to me is the audio, the transonic vapor, how fast the sky went black, how far up sound is still traveling, how quickly components burned even for the few seconds each element of the booster was exposed during the tumble, and a raw reminder of the often overlooked terminal velocity of our ships at low alt.

All little details the astute ref can make use of to make takeoff, reentry and associated hijinx more real.

Yes, there are details that can be taken away. I absolutely agree with that. It's the reason I made the analogy of watching a Spanish galleon launch rather than saying that there's absolutely no similarity between the two. The sky may go black faster than you think, but will it go black anywhere near as fast as in the video? Honestly, I've got no idea. Like I said, I would imagine that the ships launch significantly slower, but then again they probably have a much more vertical profile. Transonic vapor is cool, but will the ship even go transonic while it is in the atmosphere? Its a necessity for modern rockets. In theory a Traveller ship could travel at 800 km per hour (well below transonic) and reach 80 km in six minutes, at which point nearly all (99.99%) of the atmosphere is below it. Considering even short hops are usually in the neighborhood of a few hours adding a few extra minutes for noise abatement is hardly unreasonable (For the record my guess is that they do still go transonic. They would just be restricted to being above some altitude such as 20 km where the sonic boom wouldn't cause a problem, but it isn't inconceivable that the altitude limit would be significantly higher, especially on wealthier planets where they might also be trying to mitigate vapor trails and things).

My real point is that people often assume that ships in Traveller behave a lot like our modern rockets. Even Marc Miller put in rules in T5 that talk about heat being generated by re-entry. An awful lot of the things we associate with going into space/coming back from space are artifacts of our highly inefficient rockets and simply wouldn't exist in the Traveller universe (I actually did some math for another thread and worked out that in Traveller you should almost never have significant heat being generated by a controlled re-entry, unless you have to renter from orbit).

 

[kilemall]

Re: noise abatement and such, my thought is the main starport of a high pop world is going to have above all airspace/safety clearance issues.

To alleviate this, I would expect a large amount of traffic to be diverted/directed to Upports, the orbital facilities, and small craft/grav vehicles handle the transloading to satellite fields all over the planet. An expensive proposition to maintain full duplicate facilities especially the customs part, but perhaps less expensive then having an interstellar commerce chokepoint or the proposition of multiple Downports with that much more congested airspace.

I would also expect the average busy starport to be located on a coast, so the ships that do do hard landings and takeoffs do so over a relatively uninhabited ocean with far less chance for catastrophe if something does go wrong.

And I expect high-G vees plotted for most ships that can do them, to both increase the variability of flight profiles and thus available airspace, and for faster throughput to get ships out the outbound 'lanes' for the next one.

Finally, for ships equipped with grav maneuver instead of a variant of reaction drives, those would be preferable for flying over populated areas at subsonic speeds for your noise abatement point, and thus may command a premium in gaining timely arrival and departure slots that are otherwise restricted.

IMTU I call those whisperliners and they are both required tech for the ecologically sensitive planets, AND are a major branding item where artificial gravity is not quite the smooth tech we and Hollywood usually play it.

 

[esampson]

. . .And I expect high-G vees plotted for most ships that can do them, to both increase the variability of flight profiles and thus available airspace, and for faster throughput to get ships out the outbound 'lanes' for the next one. . .

Actually, I would imagine that variability of flight profiles is something that ground control would want to avoid. Much better to have predictable flight paths. People queue up an an altitude a couple of hundred km out and then everyone follows more or less the same line in, the same way we do with modern airports.

Leaving at higher speeds doesn't actually increase throughput because you have to increase the distance between each ship. If you think of it in terms of the old suggested 'two second gap' that a lot of us are taught for driving then you're theoretical maximum is 30 ships per minute. It doesn't matter if you are travelling at 30 miles an hour or 300 miles an hour (ok, there is a small difference because the length of the vehicle gets through faster, but that difference is minor and see below). In fact the 'two second rule' is somewhat arbitrary and the truth of the matter is that as speeds increase that length of time should also increase because it takes longer to slow down vehicles at higher speeds, which is why we never land jumbo jets two seconds apart, so higher speeds can actually reduce throughput. It's counter intuitive but true (this is part of the reason traffic jams occur. They can actually have higher throughput and are better able to deal with more cars).

Which isn't to say your idea couldn't work. Given computer capabilities and things it is quite possible that spaceports would have multiple 'lanes' for different rated vehicles. I'm just saying it isn't a given. I would think the benefits, while existing, would be minimal and may be overwhelmed by issues of social convention/comfort (we do lots of things that aren't as efficient as they absolutely could be due to issues of social convention and comfort).

On the other hand social convention and comfort is extremely fluid. 50 years ago people rarely used credit cards and would have found the idea of going to a machine to get money from their bank account uncomfortable and off-putting (what if the machine makes a mistake?) so it is quite believable to have a space port where there are hundreds of different flight paths for different ships all coordinated by computer. I'm just playing Devil's Advocate in this case and offering alternative interpretations.

 

[kilemall]

By variability of flight profile I don't mean changing lane standards on the fly, but rather that more lanes are possible the more Gs a ship can put on which would be desirable for maximizing airspace usage.

So since FT Beowulf is one of say many hundreds of 1 G craft, they are limited to specific lanes to service their limited potential flight profiles, and it may be hours getting up or down, as opposed to say a 4G liner that really can 'go vertical' readily.

However, the mix of craft would likely change from day to day and so many busy ports likely WOULD alter some lane assignments based on load and capability.

Unless 'that is just not done here on my watch mister'. Convention and comfort as you say.

As to throughput, we are talking differences similar to a Cessna vs. a Concorde, not 747 to 737.

Inbound yes there would be similarities of landing profile (although perhaps not in braking), but outbound the 4-G+ crowd is going to be gone in fractions of the time for the more 'commercially viable' craft.