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corsairealgerien t1_j6hnt3s wrote

Reply to comment by Creepy_Toe2680 in NASA tested new propulsion tech that could unlock new deep space travel possibilities by Creepy_Toe2680

Is there a similar estimate as to the difference RDRE would make? Or is it more the case of RDRE being more efficient in fuel terms, allowing for longer flights, rather than making them faster per se?

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danielravennest t1_j6ih89p wrote

In theory the RDRE would improve chemical rocket efficiency by about 10%. There is a finite amount of energy in any fuel/oxidizer combination set by the chemistry. Regular rocket engines use a turbopump to push the ingredients into a combustion chamber at high pressure. The expansion of the resulting hot gas is what turns into thrust.

The RDRE feeds the ingredients at lower pressure, and uses a detonation to create the high pressure for expansion. The energy otherwise used to run the turbopumps is then directly used for thrust. Turbopumps generally tap off some of the fuel and oxidizer flow to power themselves.

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ProgressBartender t1_j6jsmk4 wrote

It’s all about exhaust velocity, there’s just a limit to have fast a combusting gas will expand out of your nozzle. Faster velocities can be reached with Ion engines, nuclear pulse engines or other future technologies.

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[deleted] t1_j6imp08 wrote

[deleted]

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danielravennest t1_j6io6qc wrote

> Bakugo's Howitzer Impact

Not familiar enough with manga physics to answer your question. I only do physics for this world :-).

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rawbleedingbait t1_j6joy60 wrote

Okay that's fine, but why haven't we been looking into spirit bomb technology?

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dave200204 t1_j6ll589 wrote

A person's chi just doesn't provide enough energy to power a rocket, IRL.

A Chi Chi powered engine might at least give you a ballistic trajectory.

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Caboose_Juice t1_j6kvl32 wrote

from what i gather, no. RDRE is basically sourcing its fuel pressure from detonations rather than a turbo pump, eliminating an auxiliary system that consumes energy. i’m not sure about anime

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AlmennDulnefni t1_j6jm5pz wrote

Those are the same thing if you have the same thrust. More efficient means less fuel mass means more acceleration from a given thrust.

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Creepy_Toe2680 OP t1_j6how4h wrote

uhh looks like i have to do some research and math here soo..

The rocket engine, according to the plan, worked for 3.2 s, accelerating the rocket to a speed of about 90 m/s, which allowed the rocket to reach an altitude of 450 m.

The detonation shockwave travels significantly faster than the deflagration wave leveraged by today's jet engines, Trimble explained: up to 2,000 meters per second (4,475 miles per hour) compared to 10 meters per second from deflagration.

i am gonna use the second one (but i don't know if it is talking about the vehicle or the wave.)

distance from mars (130,000,000 km)

speed of detonating engine = 2km/s

so, 130000000/2= 65000000 seconds = 752.31481481 days or 2 years and 22 days.

not sure don't quote me on this.

edit: YES I knew it i was right that i was wrong!

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wgp3 t1_j6iebfv wrote

Unfortunately that's just all wrong. The part you took from the second source isn't even about the rotating detonation engine but the detonation pulse jet engine. Maybe the exhaust velocities are the same but I doubt it. And the figures used aren't even the actual exhaust velocities. That's the speed of the Shockwave from the detonation and the speed of the wave from deflagration.

But rocket engines use something called a de laval nozzle. Designed for the flow to speed up to Mach 1 at the throat and then go supersonic out the back. So the exhaust velocity of a typical rocket engine is already in the several km/s range. For example, rs25 has an exhaust velocity of about 4 km/s. Twice that of the figure you used for the detonation engine.

You can't easily just take an exhaust velocity and calculate how long a trip to mars would take. The exhaust velocity is not a limit on how fast the rocket can go. It's more about showing its efficiency. Higher exhaust velocities are more efficient. This is also measured in a term called Isp, specific impulse. Which is why ion thrusters are so efficient. They cam have effective exhaust velocities of about 40 km/s.

With effective exhaust velocity (which I'm not sure 2km/s is it for an rde) you'd at least need the initial (or wet mass, aka fully fueled rocket mass) and final mass (dry mass, mass after burning all propellant) to get the total delta v from the rocket equation. That would give you a rough idea of where the rocket can get you. The more delta v the faster you can get somewhere.

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danielravennest t1_j6ii1ae wrote

That's not how rockets work. Vehicle speed changes as your run the engine and produce thrust (push). Earth and Mars already are in orbit around the Sun. To get to Mars, you have to change your orbit so the other end crosses Mars' orbit at the same time Mars is at that point.

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corsairealgerien t1_j6hppu5 wrote

2 years and 22 days? But the original quote said it takes 6 months to get to Mars at the moment?

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Creepy_Toe2680 OP t1_j6hpwar wrote

various factors affect this such as vehicle size and many more

maybe my calculation is wrong.

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buffetcaptain t1_j6hup2p wrote

The distance to Mars changes depending on the respective orbits, at the closest point it's about half that.

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Testimones t1_j6lv9yr wrote

No no, you have it all wrong, the planets are all fixed to transparent spheres rotating around Earth, even the old greeks knew that!

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LegitimateGift1792 t1_j6mynsv wrote

I gave you an upvote even though you did not use the obligatory /s. It was the transparent spheres i liked the best.

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