Space and Astronomy in general

Gremlin wrote:

I'm worried that the budget and aggressive moon plans will lead to a big flashy start that will have schedule slip and no allocation for maintaining any of it.

I'm worried that a politically directed budget and aggressive plans is how we got Apollo 1, Soyuz 1, Challenger, and Columbia.

Robear wrote:

Yes, Gaald, until the SLS actually launches, it will be the biggest in use. 70 ton capacity for the Falcon Heavy, development cost of $500M so far.

Got a source for that development cost?

Seems amazing low, but maybe that's just that I'm looking at it from deep within the military-industrial complex.

Robear wrote:

Yes, Gaald, until the SLS actually launches, it will be the biggest in use. 70 ton capacity for the Falcon Heavy, development cost of $500M so far. 77 ton capacity for the SLS, with later enhancements planned to get to 130 tons, at a cost (so far) of $23B. Yes... 46x as expensive as the Falcon Heavy to develop...

I'm not even talking about that one. I'm talking about the BFG or Starliner, whatever they are calling it these days.

The Starliner is the Boeing crew capsule... Still not clear on exactly what you're talking about.

Jonman wrote:
Robear wrote:

Yes, Gaald, until the SLS actually launches, it will be the biggest in use. 70 ton capacity for the Falcon Heavy, development cost of $500M so far.

Got a source for that development cost?

Seems amazing low, but maybe that's just that I'm looking at it from deep within the military-industrial complex.

I wasn't able to find a direct quote from Musk/SpaceX on that number within 10 minutes of searching, but that 500 million number was in a lot of articles, like this one for example.

NSMike wrote:

The Starliner is the Boeing crew capsule... Still not clear on exactly what you're talking about.

Sorry I meant the SpaceX BFR now called Starship. I thought that was going to be the biggest. Capable of 150 tonne payload. Or did that get downgraded again?

WizKid wrote:

I wasn't able to find a direct quote from Musk/SpaceX on that number within 10 minutes of searching, but that 500 million number was in a lot of articles, like this one for example.

Hmm, yeah. Maybe I'd buy $500mil to develop Falcon Heavy if that was in addition to the sunk costs of developing Falcon (non-Heavy).

For instance, how many RUDs have SpaceX had, and what's the cost of each of them in lost hardware? I struggle to see how they're all included in that $500mil with space left over to pay their engineers.

The number I saw for Falcon 9 was 1 billion, so lets say 1.5 - 2 billion for both Falcon 9 and Falcon Heavy. Lets be generous and double that again and make it an even 4 billion for R&D. You're still no where close to the cost of the still unfinished development of SLS, and that's not even taking into consideration the launch costs.
SpaceX truly is a radical paradigm shift in the cost of space travel, and that's not even taking into consideration BFR which will be even cheaper to launch.

Ars Technica wrote:

Consider just a single data point: NASA annually spends about $2.6 billion to develop the SLS rocket and ground launch systems for the massive rocket at Kennedy Space Center. The SLS rocket was originally supposed to launch in 2017, but now the maiden flight of the SLS booster has slipped to 2020. That is understandable; most large aerospace rockets experience delays. However, the cost of a three-year delay is $7.8 billion.

For the sake of argument, consider the costs of this three-year delay against the lift capability NASA could have bought by purchasing Falcon Heavy rockets from SpaceX in 2018, 2019, and 2020. That $7.8 billion equates to 86 launches of the reusable Falcon Heavy or 52 of the expendable version. This provides up to 3,000 tons of lift—the equivalent of eight International Space Stations or one heck of a Moon base.

Source

Oh, and SpaceX had a launch tonight, too.

Cool moon pic taken recently when Jupiter was near moon in the sky. Two exposures used: one for moon and one for Jupiter + 4 of its moons. Captured using only Canon 1200D with 200mm lens. (Source)

IMAGE(https://i.redd.it/jozouyniik031.jpg)

Wow! That's cool.

So how would a nozzle increase the effectiveness of an estes solid rocket motor?

Intuitively, I think the bell shape would better contain the thrust downwards. Estes engines, from my own experience, have a pretty tiny nozzle that sprays a lot out to the side. Containing the exhaust, channeling it through a small hole again and releasing it via the bell should give more push directly down.

Am I right?

Vnozzle is your primary thrust determinant, cos kinetic energy of the exhaust flow is mv^2, right?

So while you're right that containing the flow so you're not losing thrust laterally due to spray is certainly a thing, I think the nuance here is that optimized nozzle design results in a faster exhaust flow, hence more thrust.

If that exhaust is subsonic you should be able to get a pretty significant improvement. From the video the shape of the nozzle shows that indeed the gas is subsonic, or it's a terrible nozzle. We are intuitively used to subsonic fluids where narrowing the nozzle makes the water come out faster, like a garden nose. Once you hit Mach 1, however the opposite is true, and expanding the region speeds up the flow. So that ubiquitous nozzle types job is to squeeze the fluid to speed it up to Mach 1, and then allow it to expand to get above Mach 1.

Comments on that video point out that an examination of the exhaust shows that there is still a lot to improve. I think this is more of a "this run didn't fail catastrophically" thing. The most obvious is that the nozzle is wider than the exhaust, which means that it's expanding too much, or isn't actually speeding it up to a supersonic flow. The flow is also super turbulent, which honestly is going to come with the engine more than anything, although if the flow was choked (Mach 1 achieved in center of bell) you would expect it to dampen out some of that excessiveness, so that's another indication that that's probably not happening.

You don't see any sign of a shock diamond, which can tell you different things about the flow, That is another sign that the flow probably isn't actually supersonic, but even with good flow I think it'd be hard to see the diamond because the exhaust is so bright, I'm guessing because there is still a lot of combustion happening after the nozzle, which once again is more of an engine issue than a nozzle issue.

It's important to note that in a setup like this both the characteristics of the burn, as well as the internal shape of the nozzle, are going to change a lot over the burn. Real rockets do a lot of fancy stuff to get as homogeneous a burn as possible.

All I know is that this kid is a high school freshman who spent ten months of trial and error using their own 3D printer to make a goddamn rocket nozzle that didn't fall apart when the engine was lit. About the only thing I stuck with for that long at that age was teaching myself Elton John songs on the piano. And look where that got me.

When I saw the video on reddit and read the genuinely curious and grateful responses from this kid, I immediately awarded the post Reddit Platinum (one month of premium) and left a message that I hope this future rocket scientist is able to help us get off this planet while it's still possible.

Yeah, I don't think the nozzle is doing anything if it's not constricting the flow any more than the built-in nozzle. But it's a 14-year old kid that's learning, I had enough people stomp on my dreams at that age, I don't need to stomp on anyone else's. The kid will figure it out, and maybe discover something new in the process.

Edit: Not to say that folks here are being mean to a kid. Just keep in mind that curious minds should be encouraged, not discouraged, if/when they're wrong.

The kid doesn't read this forum (he doesn't have a job!) I was quite happy to read a bit about the dynamics of rocket exhaust and nozzles!

You're not my real dad!

I might be projecting a little.

Researchers solve mystery of the galaxy with no dark matter

Using five independent methods to estimate the distance of the object, they found that all of them coincided in one conclusion: The galaxy is much nearer than the value presented in the previous research.

The original article published in Nature stated that the galaxy is at a distance of some 64 million light years from the Earth. However, this new research has revealed that the real distance is much less, around 42 million light years.

Thanks to these new results, the parameters of the galaxy inferred from its distance have become "normal," and fit the observed trends traced by galaxies with similar characteristics.

The most relevant datum found via the new distance analysis is that the total mass of this galaxy is around one-half of the mass estimated previously, but the mass of its stars is only about one-quarter of the previously estimated mass. This implies that a significant part of the total mass must be made up of dark matter.

That is an awesome diagram. I would kill for that to be interactive and 3D at a musuem

bigred wrote:

That is an awesome diagram. I would kill for that to be interactive and 3D at a musuem

It's not interactive, but the original source of the diagram (Emily Lakdawalla of the Planetary Society) does update it periodically.

What happened to Teegarden A?

We don't talk about Teegarden A.