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Is Blue The Only Color For The Exhaust Plume Of An Uber Pulse Rocket?


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Just wondering... for fictional reasons.

 

Spoiler

Due to all the problems associated with SSTOs I have finally decided to allow gravity suspension field generators... which allow spacraft to float weightlessly on a planet.

Rocketry is still required, but I settled on using two normal chemical rocket engines for less efficient lower powered manuevering, and a middle main engine that has the same energy as a fusion pulse.... but it is not necessarily fusion.

 

It could be some exotic engineered superfuel.

 

In which case, I think blue will always be the plume color... or could it be white? Or would that be too hot?

 

 

Edited by Spacescifi
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So you want to use (magical) gravity suspension generators... and chemical maneuvering rockets? :lol:

Sorry, but to me it looks like someone wanting to put oars on a nuclear aircraft carrier.

Plus yet another fusion pulse (but not really) engine.

Why are you so overcomplicating things?

If you want to write hard sci-fi story, don't dabble in clarktech. If you want to write space opera, go full ham on unobtanium.

Or just flat out state that the setting is post-apocalyptical one. Survivors have to piece together fragments of surviving technologies, while barely understanding how it all works. Make use of frankentech necessity, because characters don't have access to anything else - just bits and pieces that barely fit together.

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Posted (edited)
12 hours ago, Scotius said:

So you want to use (magical) gravity suspension generators... and chemical maneuvering rockets? :lol:

Sorry, but to me it looks like someone wanting to put oars on a nuclear aircraft carrier.

Plus yet another fusion pulse (but not really) engine.

Why are you so overcomplicating things?

If you want to write hard sci-fi story, don't dabble in clarktech. If you want to write space opera, go full ham on unobtanium.

Or just flat out state that the setting is post-apocalyptical one. Survivors have to piece together fragments of surviving technologies, while barely understanding how it all works. Make use of frankentech necessity, because characters don't have access to anything else - just bits and pieces that barely fit together.

 

That's actually a good premise.... like a get out of jail free card for not having to explain the unexplainable.

 

As for fusion pulse energy rockets... you may wonder why the obsession?

Well... I happen to think that an uber high thrust rocket with only 300 seconds of ISP is probably more likely to be realistic than some 1g torchdrive rocket that can burn for hours or even days.

 

That's essentially what I am going for.... 300 seconds ISP is not great but with gravity suspended and high thrust pulsed burns the 300 seconds can last you a good while. Coast the rest of the time anyway.

 

When only a few pulse burns are needed to reach space, that is very fuel efficient.

 

I was thinking to just make up some super-fuel source on par with pure fusion for energy and effect to not have to worry about all the issues with uber magnets, explosives, and inertial confinement.

 

Need something at least relatively safe... and fusion... at least high thrust fusion... is not that lol.

Edited by Spacescifi
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1 hour ago, Spacescifi said:

When only a few pulse burns are needed to reach space, that is very fuel efficient.

300 ISP is 300 ISP. Burning your fuel faster, doesn't male it more efficient.

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At some point you're going to realise that 'science fiction' is a sliding scale and adding more 'science' will restrict the 'fiction' part, and vice versa. Unless you're looking for documentary-level details, making things vague gives you a lot more wiggle room so unless it's absolutely critical to spell out exactly what combination of propellants or fusion reactor design is involved, don't.

James Holden never expounds on the inner workings of the Rocinante's fusion torch drive, Honor Harrington doesn't wax lyrical about the magic space-bending, 600g-accelerating inertial drives that yeet skyscraper-sized spaceships around her neck of the galaxy, and any attempts to try and pseudoscience Star Wars come across as exactly that.

You don't need to know exactly how a jet engine works to write a contemporary story involving planes, just that it sucks in air at the front, adds fuel in the middle and produces thrust at the back. If that's good enough for technology that's been in use for nearly a century, why be any more detailed about fictional future technology? Throwing buzzwords at it and hoping something sticks is going to produce an incoherent soup of confusion and contradiction, making life harder for reader and writer alike.

 

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2 hours ago, Shpaget said:

300 ISP is 300 ISP. Burning your fuel faster, doesn't male it more efficient.

 

When gravity is essentially turned off and you only need a few pulse burns to reach space then you save fuel... I think.

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3 hours ago, jimmymcgoochie said:

Honor Harrington doesn't wax lyrical about the magic space-bending, 600g-accelerating inertial drives that yeet skyscraper-sized spaceships around her neck of the galaxy

We are getting off-topic, but David Weber is NOTORIOUS for making huge "datadumps" about his imagined tech. This is not a very good example of what you are trying to say.

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4 hours ago, Spacescifi said:

 

When gravity is essentially turned off and you only need a few pulse burns to reach space then you save fuel... I think.

You save 1.6 km/s of 9.6.

One sixth of required fuel.

If the annti-gravity is not magic, then you save twice less, because the antigravitator still needs same energy to work.

At least, m * g * (h2-h1)

It's just like permanently creating a 1 g thrust.

(Unless it's a magic cavorite pod.)

Edited by kerbiloid
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5 hours ago, Spacescifi said:

 

When gravity is essentially turned off and you only need a few pulse burns to reach space then you save fuel... I think.

That's like saying that you can pour more water out of a bucket if you pour faster.

ISP is the measure of how efficient the rocket engine is at using the reaction mass. If you lock it in, then the efficiency is fixed.

 This is the rocket equation:

{\displaystyle \Delta v=v_{\text{e}}\ln {\frac {m_{0}}{m_{f}}}=I_{\text{sp}}g_{0}\ln {\frac {m_{0}}{m_{f}}},}
Neither the thrust, nor the briefness of the pulses is anywhere to be seen.
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38 minutes ago, Shpaget said:

That's like saying that you can pour more water out of a bucket if you pour faster.

ISP is the measure of how efficient the rocket engine is at using the reaction mass. If you lock it in, then the efficiency is fixed.

 This is the rocket equation:

{\displaystyle \Delta v=v_{\text{e}}\ln {\frac {m_{0}}{m_{f}}}=I_{\text{sp}}g_{0}\ln {\frac {m_{0}}{m_{f}}},}
Neither the thrust, nor the briefness of the pulses is anywhere to be seen.

 

Alright so I guess I was in error using ISP.

 

Ultimately I just want an uber pulse rocket that can get lots of thrust from small amounts of fuel combusting..

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Then just have it. Skip the details and have a ship that can do multiple orbital launches and landings, with interplanetary (or interstellar) travel inbetween occasional refuelling. You don't need to provide the blueprints for the engines. Just have them do whatever you want them to do that is needed for the story. If you later realize they're OP, have a malfunction in the gefufen oscilator, or the antagonist discovers a way to track your ship, or there is an administrative delay because one of the crew decided to transport the Blomulaxian pentaworm which is, obviously, not allowed. Noone cares about ISP in scifi.

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1 hour ago, Shpaget said:

Noone cares about ISP in scifi.

This is an overstatement.

For example, one of the most famous SF short stories, "The Cold Equations", got all of its drama and shock value out of a small landing shuttle not having enough delta-v to safely land with a stowaway on board. Another example is the drama in The Martian relating to the MAV not having enough delta-V to match velocity with the ship coming to pick up Watney. (Also in the same book, it was a plot point that the crew on the transfer ship had to do gravity assists with Earth and Venus in order to get back to Mars before his food ran out.) Etc., I can think of many more where some aspect of rocket design, orbital mechanics, delta-v limits, etc. played a plot role.

The thing is, none of them were good because they had solar sails or ion drives or whatever. They were good (or not) because of the writing, the plotting, the theming, the characterization....

Heck, I vividly remember one short story about space travel that was powered by philosophers -- if they just completely convinced themselves that the ship had traveled to its destination, it did! But on this particular ship one of the philosophers secretly doubted that it would work and panicked and prayed to God, and the whole ship ended up in Heaven instead.

Edited by mikegarrison
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59 minutes ago, mikegarrison said:

This is an overstatement.

For example, one of the most famous SF short stories, "The Cold Equations", got all of its drama and shock value out of a small landing shuttle not having enough delta-v to safely land with a stowaway on board. Another example is the drama in The Martian relating to the MAV not having enough delta-V to match velocity with the ship coming to pick up Watney

Not quite the same thing. Examples you provide boil down to "We don't have enough fuel to do x".

OP proposal to explicitly state and specify the ISP of 300 s is "Our car has a fuel economy of x mpg, therefore we need to go faster to reach our destination." which is not only non sequitur, but also ISP 300 s is not something that will provide "lots of thrust from small amounts of fuel combusting" (again, unrelated things, not to mention that a rocket with that kind of ISP absolutely will need a lot of fuel to reach orbit, physics breaking magical grav nullification or not).

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I think David Weber's stories are a good example.  As I recall he goes into great detail about the *implications* of the technologies and how they can be used tactically. Does it matter how efficient the Bomb-pumped X-ray laser is? No. What matters to the reader is they're proximity weapons that don't need a contact hit to cause damage.

Reader: Ok, cool, understood.

Another example, Jump Gates. How do they work? Doesn't really matter. The plot relevant details are that they're faster than regular FTL, and get destabilised by the amount of mass they transit. So you can send light cruisers through basically continuously, but if you send a battleship it will destabilise the jump point for several minutes and if you send an entire fleet you'd better hope it doesn't need reenforcements or to retreat any time soon. This creates a PROBLEM, and it is the solution to the problem that is interesting, not the minutae of how the gate actually functions.

Edited by RCgothic
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13 hours ago, mikegarrison said:

We are getting off-topic, but David Weber is NOTORIOUS for making huge "datadumps" about his imagined tech. This is not a very good example of what you are trying to say.

OK, I’ll admit that I picked that example because I could remember both the main character’s name and the propulsion system; I’ve read all of two books in the series and that was a few years ago now.

Point is, the more details you add the more they box you in and the more likely it is that you’ll end up having to retcon some extra details into the system to then handwave your way past them to make some critical piece of plot work. Let the reader do some work for you.

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5 hours ago, jimmymcgoochie said:

OK, I’ll admit that I picked that example because I could remember both the main character’s name and the propulsion system; I’ve read all of two books in the series and that was a few years ago now.

Point is, the more details you add the more they box you in and the more likely it is that you’ll end up having to retcon some extra details into the system to then handwave your way past them to make some critical piece of plot work. Let the reader do some work for you.

True... so I am going to presume that any high thrust pulse rocket would a have bluish exhaust plume of some sort, since coloration if I read correctly is more variable the cooler the exhaust and less so the hotter it is?

Could be a solid white plume too I suppose....

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17 hours ago, Shpaget said:

Color of the exhaust is related to its temperature, not the amount of thrust.

Take a look at Space Shuttle. SRBs have much higher thrust than SSMEs.

A lot of the smoke plume from the SRBs has to do with the chemicals being burnt and the large leftover particles.  Certainly the thrust has a lot to do with it: you can't see the exhaust of a SSME, but you certainly can see the white-hot plume of a Delta III (both hydrolox), but SRBs tend to have stuff that doesn't necessarily turn into gas.

Some of this is likely similar to changing the color of the plum via oxidizing chemicals, like coloring fireworks.

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On 8/9/2022 at 2:55 PM, Spacescifi said:

That's actually a good premise.... like a get out of jail free card for not having to explain the unexplainable.

Want a better one?

Don't write yourself into a corner to begin with.  The more technical details you give to your audience, the more you tie your own hands behind your back with regards to creating and resolving drama.

Examples:

A) My ship has a Delta-V of X and a fuel fraction of Y, and I need to get this vaccine to the planet just hit by a plague within W hours or everyone there will die.  he plague planet is Z distance away, I hope we can make it!  

B) A plague hit Planet X!  We are the only ship with a hope of getting there in time, and only if we <Technobable> the <Technobable>, and then push the <Technobable> beyond safe levels! 

With A, anyone who knows enough to understand all the numbers you throw out about the ship will know right away if the ship can get there in time, and anything else will be obvious deus-ex-mahina.  

With B you can have <Technobable> break-down from pushing it too hard and lots of dramatic struggles and risks to make it on-time with no known outcome until the end.

 

Not to mention, providing technical details does nothing productive with regards to building or maintaining dramatic tension.  For the sake of your readers, do not make your story into a technical manual.

On 8/9/2022 at 2:55 PM, Spacescifi said:

When only a few pulse burns are needed to reach space, that is very fuel efficient.

Making a thrust shorter does not in any way make it more fuel efficient.

Usually the inverse actually, as lower-thrust engines are usually more efficient, especially things like ion engines that run for days but could not lift a piece of paper off of a table on earth.

On 8/9/2022 at 2:55 PM, Spacescifi said:

I was thinking to just make up some super-fuel source on par with pure fusion for energy and effect to not have to worry about all the issues with uber magnets, explosives, and inertial confinement.

Generally speaking, energy density is the antithesis of safety.

 

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28 minutes ago, Terwin said:

Making a thrust shorter does not in any way make it more fuel efficient.

Low thrust = long acceleration = more gravity delta-V loss, g * t; say,  at TWR=1 the ship will spend all its fuel on the gravity loss.

High thrust = high drag = more air drag delta-V loss, v2 and the possibility of the ship melting

The optimal acceleration (i.e. thrust) is in between. For space rockets 1.2 g at ground, for ICBM ~2 g.

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