The "Real Aerospace" Thread

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Mjolnir
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Re: The "Real Aerospace" Thread

Post by Mjolnir »

Zarya wrote:
Mjolnir wrote:edit: Correction, the Vulcain is actually a gas-generator engine like the Merlin. It pumps both fuel and oxidizer into the chamber with a pump driven by a turbine running from a small fraction of the propellant flow and dumping its exhaust separately. Simpler to develop but less efficient.
heh - you're more than 99% right about the Vulcain, although it also re-injects the exhaust product of the pre-burner to create a 'film' inside the engine that protects the nozzle & engine bell. The original idea to create a slightly cooler chamber wall by injecting something extra, such as fuel, dates back to the A4 motor that powered the V-2 and it was also applied in the F-1 used for the Saturn V. My point: the Vulcain is not simply dumping the exhaust product of the pre-burner over the side, while not being a full-blown staged combustion either.

The Bristol Siddeley Gamma is brilliant in its own right, it applies the properties of H2O2 to achieve "staged combustion like efficiency".
It's a pretty standard technique, the Merlin 1D Vacuum does the same, but the turbopump exhaust contributes little to thrust, it just lets you use a lighter nozzle extension. It's still a gas generator cycle, with the limitations on chamber pressure and less efficient use of reaction mass that come with it...the Vulcain only runs at 100 bar, the Merlin 1D at 97 bar. The RS-25 runs at 206 bar, RD-180 at 270 bar. The Vulcain gets a vacuum Isp of 431 s, compared to the staged combustion RS-25's 452 s. The Merlin 1D's 311 s is quite good for a kerosene burning gas generator engine, but the staged-combustion RD-180 gets 338 s.

Raptor gets 380 s with methane...near the performance of hydrogen with a far denser propellant that's a close match in physical properties to liquid oxygen.

The Gamma: that depends on how brilliant you consider using HTP to be. As far as I'm aware, the Black Arrow was the only launch system in existence to ever get to orbit using HTP as an oxidizer, which it did exactly once before being canceled. Many others have tried, with the expectation that a room temperature oxidizer would be easier to work with than cryogenic oxygen, but nobody's succeeded. Instead, the main room temperature alternative to LOX has been nitrogen tetroxide. People get misled by thinking of the heavily diluted stuff you can buy in the store, hydrogen peroxide in high concentrations is quite dangerous and difficult to handle. (Its instability is the reason the Soyuz can't stay longer at the station...the Soyuz uses it for attitude control, but it decomposes over time no matter what you do.)

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Zarya
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Re: The "Real Aerospace" Thread

Post by Zarya »

You're right about the Vulcain as well as about the higher chamber pressures - up until the late 1990s considered 'extreme' - for closed-cycle/staged combustion engines. Although the RD-180 is still used to launch NRO satellites and has a spotless track record, it has never been man rated, presumably because of the chamber pressures.
The Raptor and in due course the BE-4 or their successors may be among the first staged combustion engines with high chamber pressures that will ever be used for manned flights. I think they will be literally have to be tested to destruction over a lengthy period before they will be trusted.

I also feel we should be kind about the Bristol Gamma: its story started well over 60 years ago in the age of slide rulers and engineers wearing woollies on stone cold test sites, with the UK looking to develop its own launch vehicles 'on a shoestring' to develop a capability that'd perhaps allow the country to field its home-grown nuclear deterrent. For the delivery vehicle they needed a storable propellant and oxidizer and for that they went with HTP. The Royal Navy already had experience with high-test peroxide for their torpedoes - including a serious mishap with it - so at that time it was probably considered not as exotic and dangerous as nitrogen tetroxide.

Looking at the Black Arrow launches the exhaust plume is super-clean and the rocket itself is relatively small. Those are all advantages. Puck/Prospero, the satellite it launched during its very last launch, is indeed still in orbit. In short HTP and kerosine allowed for a very efficient launcher that was never adequately funded and that came too early to lift commercial payloads into orbit.

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Mjolnir
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Re: The "Real Aerospace" Thread

Post by Mjolnir »

Zarya wrote:You're right about the Vulcain as well as about the higher chamber pressures - up until the late 1990s considered 'extreme' - for closed-cycle/staged combustion engines. Although the RD-180 is still used to launch NRO satellites and has a spotless track record, it has never been man rated, presumably because of the chamber pressures.
The Raptor and in due course the BE-4 or their successors may be among the first staged combustion engines with high chamber pressures that will ever be used for manned flights. I think they will be literally have to be tested to destruction over a lengthy period before they will be trusted.

I also feel we should be kind about the Bristol Gamma: its story started well over 60 years ago in the age of slide rulers and engineers wearing woollies on stone cold test sites, with the UK looking to develop its own launch vehicles 'on a shoestring' to develop a capability that'd perhaps allow the country to field its home-grown nuclear deterrent. For the delivery vehicle they needed a storable propellant and oxidizer and for that they went with HTP. The Royal Navy already had experience with high-test peroxide for their torpedoes - including a serious mishap with it - so at that time it was probably considered not as exotic and dangerous as nitrogen tetroxide.

Looking at the Black Arrow launches the exhaust plume is super-clean and the rocket itself is relatively small. Those are all advantages. Puck/Prospero, the satellite it launched during its very last launch, is indeed still in orbit. In short HTP and kerosine allowed for a very efficient launcher that was never adequately funded and that came too early to lift commercial payloads into orbit.
The BE-4 actually has a weirdly low chamber pressure. Only 134 bar, more in line with a high-end gas generator engine than a staged combustion engine. It's their first large engine, so perhaps they're just being very cautious with its design. (Though they've also had problems bringing it up to full thrust, so maybe there's other issues.)

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White
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Re: The "Real Aerospace" Thread

Post by White »

The Starship SN5 hopped succesfully.

Scott Manley has a video on it.



Also, SpaceX released some footage.


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Arioch
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Re: The "Real Aerospace" Thread

Post by Arioch »

Flying silos! It must be tornado season in Nebraska!

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Ithekro
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Re: The "Real Aerospace" Thread

Post by Ithekro »

Looks like a chrome propane tank.

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White
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Re: The "Real Aerospace" Thread

Post by White »

Arioch wrote:
Wed Aug 05, 2020 10:16 pm
Flying silos! It must be tornado season in Nebraska!
Mars Needs Maize!

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Re: The "Real Aerospace" Thread

Post by Krulle »

IF then the tornado was astonishingly gentle with the silos.
Not even one grain of corn spilled.
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Re: The "Real Aerospace" Thread

Post by Arioch »

Image

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GeoModder
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Re: The "Real Aerospace" Thread

Post by GeoModder »

But... there's a black outline at the tail's edge... :P
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Zarya
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Re: The "Real Aerospace" Thread

Post by Zarya »


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Arioch
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Re: The "Real Aerospace" Thread

Post by Arioch »

Flying VF-1J and VF-1S Valkryries.
Well... just barely.

Sweforce
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Re: The "Real Aerospace" Thread

Post by Sweforce »

Arioch wrote:
Fri Aug 14, 2020 7:19 pm
Image
Fake or real this is really funny but immensely more so if it is real and thus a joke in itself. :lol:

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Re: The "Real Aerospace" Thread

Post by Krulle »

Sweforce wrote:
Mon Nov 02, 2020 12:40 pm
Arioch wrote:
Fri Aug 14, 2020 7:19 pm
Image
Fake or real this is really funny but immensely more so if it is real and thus a joke in itself. :lol:
seems to be real:
https://space.stackexchange.com/questions/23021/is-this-attach-orbiter-here-note-black-side-down-sign-on-the-shuttle-carrie
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Re: The "Real Aerospace" Thread

Post by Arioch »

While this video is about how cameras track hypersonic objects, it contains an interesting compilation of railgun projectiles and more conventional tank rounds in flight.

What I find particularly interesting is how the shock waves create by the round are clearly visible in normal light.


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Re: The "Real Aerospace" Thread

Post by Krulle »

This technology of tracking very fast elements is also being developed more and more.
The first military systems are online in the hope they can find, track, and deliver targeting data to interceptor missiles for hypersonic rockets.

It's a question of how much sky you can scan though.
The processing capabilities are limited.

Visual systems also have the disadvantage of being reliant on weather conditions.

Still a very interesting video. I found the part about the ping-pong ball interesting, haven't seen that before.
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Re: The "Real Aerospace" Thread

Post by Arioch »

Good point. Since the beam side of the future weapons equations probably begins with lasers, fast-tracking mirrors are quite significant. And I think a mirror that can track a Mach 7 projectile probably has all the performance characteristics you'll need to focus a beam on an incoming target, even if it's a hypervelocity missile.

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Re: The "Real Aerospace" Thread

Post by Sweforce »

Arioch wrote:
Fri Nov 06, 2020 8:54 am
Good point. Since the beam side of the future weapons equations probably begins with lasers, fast-tracking mirrors are quite significant. And I think a mirror that can track a Mach 7 projectile probably has all the performance characteristics you'll need to focus a beam on an incoming target, even if it's a hypervelocity missile.
A reason to use beam weapon is the fact that they give absolutely no warning for point defense systems to react. Perhaps the damage can be mitigated by releasing some kind of mirroring materials but by the time you know that you should have used that option it is already to late. The beam travels at the speed of light and as such it cannot be detected before it hits. If the beem is focused enough, a beam fired in the vacuum of space cannot even be detected if it misses! As such, the best a hope is evasive actions as soon as there is a possibility of being fired upon and that will be a drain on the fuel reserves.

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elorran
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Re: The "Real Aerospace" Thread

Post by elorran »

To add to the camera topic... insanely high speed camera capturing a pulse of light with a mirror included. And this was 2010-2011.
https://youtu.be/EtsXgODHMWk

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Re: The "Real Aerospace" Thread

Post by GeoModder »

Sweforce wrote:
Sat Nov 07, 2020 11:53 am
The beam travels at the speed of light and as such it cannot be detected before it hits.
That's where quantum spooky action at a distance comes into play.
Image

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