The "Real Aerospace" Thread

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Mjolnir
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Re: The "Real Aerospace" Thread

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icekatze wrote:hi hi

Actually, the Fastrac was heavier than the Merlins, but whatever. Tweaking the nozzle was cool and all, but it is still an iteration on past work. I look forward to seeing if they can succeed in making recovery cost effective, they've got one step out of the way, I'll be sure to follow them along the next few.
Fastrac was indeed nearly twice the mass, at 910 kg compared to 470 kg, but nobody measures rocket engine size in mass. The Fastrac only had 284 kN of vacuum thrust, compared to 825 kN for the latest up-rated Merlin 1D...the Merlin is nearly 3 times larger. It would take 25 Fastrac engines to match the sea level thrust of a Falcon 9. The T/W ratio of the Merlin 1D is 180...Fastrac was 32. Yes, Fastrac had an utterly abysmal T/W ratio, while the Merlin sets records.

Fastrac had an ablatively-cooled combustion chamber and expendable carbon fiber nozzle, Merlin has a regeneratively cooled combustion chamber and a radiatively cooled niobium alloy expansion nozzle.

Fastrac was fixed thrust, set prior to launch, the avionics were limited to opening and closing valves and firing an expendable ignition cartridge. The Merlin 1D can throttle down to at least 70% (possibly more with the recent updates to the 1D), quickly and precisely enough to allow landing of the first stage. Merlin is also capable of relighting multiple times in a single flight.

Merlin has a vacuum variant with even higher thrust and far deeper throttling, down to 39%. There'd be little point in even trying to put a Fastrac on an upper stage.

SpaceX also makes heavy use of 3D printing to reduce complexity and manufacturing costs and improve performance, including parts of the Merlin engines...a technology that didn't even exist when Fastrac was canceled.

They didn't "tweak the nozzle", they developed a series of several new engines, and several launch vehicles using them. At best, they used the Fastrac design as a reference while designing the Merlin 1A...they immediately went well beyond it. The 1C and 1D aren't even entirely the same kind of engine, they both are regenerative cooling designs and each takes a very different approach to combustion chamber construction, while Fastrac used a thick layer of phenolic composite ablative material.

As for the notion that SpaceX could cobble together a few over-budget, behind-schedule, canceled NASA projects into a medium-heavy launch vehicle that operates with a small fraction of the launch costs of the competition...really? They're reducing costs by blindly copying designs from an organization that has consistently failed miserably at reducing costs? Do you honestly not see how absurd an idea that is?

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Re: The "Real Aerospace" Thread

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Mjolnir wrote:Do you honestly not see how absurd an idea that is?
There was really no need to add this insulting comment at the end of your argument.

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Re: The "Real Aerospace" Thread

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hi hi

Like I said, they upgraded the turbo pump to have a higher flow rate, something that was within the design's capabilities, though never utilized in testing. Regenerative cooling is certainly nothing new (late 1800s, early 1900s), you put tubes around the engine bell and pump propellant through it, that's hardly a revolutionary design change. Not to mention the fact that the Merlin gets its excellent thrust to weight ratio at the expense of specific impulse.

And after speaking with people who work on space launches, I will continue to maintain that the engine was only one of many examples of places where Space X got free assistance from NASA. Which is fine for them, and honestly the US space industry could use the cooperation.
a small fraction of the launch costs of the competition
I mean, I guess qualitative size is open to interpretation, but I personally think that 13402 dollars per kilogram (Falcon 9) is not a small fraction of 13725.5 dollars per kilogram (Long March 3B) to GTO. The Atlas V is actually better, costing less than 11494.25 dollars per kilogram to GTO. (The ULA also gets plenty of free assistance.)

Space X is a fine company, and I've been trying to give them credit where it is due this entire time, but I don't think they are the second coming of space Jesus. If and when they manage to prove that they have a reliable, reusable launch system that reduces costs, then I will happily give them credit for that as well.

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Re: The "Real Aerospace" Thread

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Re: The "Real Aerospace" Thread

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icekatze wrote:Like I said, they upgraded the turbo pump to have a higher flow rate, something that was within the design's capabilities, though never utilized in testing. Regenerative cooling is certainly nothing new (late 1800s, early 1900s), you put tubes around the engine bell and pump propellant through it, that's hardly a revolutionary design change. Not to mention the fact that the Merlin gets its excellent thrust to weight ratio at the expense of specific impulse.
No, it's not "like you said" at all. These are not even close to being the same engine with a different turbopump and "tubes around the engine bell" (which is not what they did and which completely misrepresents the engineering issues involved).

As for launch costs, I don't know where you got them, but your Atlas V numbers are way off. With the current no-reuse Falcon 9 prices, for GTO, Falcon 9 is $12600/kg, which is about 1/3 of the ~$35000/kg an Atlas V would cost. At your $11494.25/kg figure, an Atlas V 551 (the highest-capability Atlas V that has launched) would only cost about $100 million, and Tory Bruno has given $164 million as the minimum cost for their lowest-end configuration (which would be the 401, with 4750 kg to GTO).

For LEO: Falcon 9 gets $4650/kg, Atlas V gets $13182/kg. About 2.8 times cheaper there.

Atlas V is simply not competitive. Of the launchers with comparable capability, only the Delta IV is more expensive. It can't even compete against the ESA launchers, let alone the Russians and Chinese. Not even ULA claims otherwise, Tory Bruno has specifically stated that they are targeting much lower prices with the Vulcan in order to compete (aiming for a target that is still higher than the no-reuse Falcon 9, but at least comparable), but they are years away from launching it. The Chinese are the only ones who have come close to Falcon 9 launch costs, and they have heavy state support.

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Re: The "Real Aerospace" Thread

Post by icekatze »

hi hi

I got the numbers from Former ULA CEO Michael Gass, and the ULA's 2014 launch contract. 164 million is the cost for a low end Delta rocket, not a low end Atlas rocket.

It is also important to note that when Space X, or anyone, does launches for the US government, there is another roughly $30 million per launch in government oversight that is not present during commercial launches.

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Re: The "Real Aerospace" Thread

Post by Absalom »

icekatze wrote:hi hi

Like I said, they upgraded the turbo pump to have a higher flow rate, something that was within the design's capabilities, though never utilized in testing. Regenerative cooling is certainly nothing new (late 1800s, early 1900s), you put tubes around the engine bell and pump propellant through it, that's hardly a revolutionary design change.
This is like saying that the Fastrak is a minor revision of the Apollo DPS. On top of that, even if you went with feature set over actual physical design (and you should almost always go with actual physical design), the current Merlins wouldn't be Fastraks (or as far as I can see, any other pintle-injector design) because none of the others had regenerative cooling. This is not a minor change, given that it means the rocket engine is not designed to engage in auto-canibalism.

If your NASA friend thinks that the Fastrak and Merlin are the same engine just because they both use a pintle injector, then they certainly don't belong in the actual launcher branch of NASA due to having a personality unsuited to the job. That kind of obsesively-invative outlook really only belongs in experimental science, not applied science, since applied is about doing things, instead of preparing for doing things.
icekatze wrote:Not to mention the fact that the Merlin gets its excellent thrust to weight ratio at the expense of specific impulse.
As long as it can achieve orbital insertion of the payload, this is perfectly reasonable. You'll never get good Isp from a chemical rocket because pure chemical rockets just can't achieve the enery / mass ratios needed, so you're better off focusing on ion engines & such as soon as you get your orbital characteristics to a state that allows them to achieve the job. I won't say that higher Isp chemical rockets are inherently bad, but if that cuts into your reusability quotient (just as an example), then you need to ditch the extra Isp, because the rockets currently cost much more than the fuel, so if you cut rocket costs by half (which a single reuse of a lower stage probably won't quite achieve) then you might get around 40% cost reductions. Fuel, meanwhile, commonly costs ~10%. Thus, reusability is more important than Isp while your reuses are few (or none), because each reuse makes more of an impact.
icekatze wrote:Space X is a fine company, and I've been trying to give them credit where it is due this entire time, but I don't think they are the second coming of space Jesus. If and when they manage to prove that they have a reliable, reusable launch system that reduces costs, then I will happily give them credit for that as well.
Funny, because it reads more like you've been trying to downplay their achievements as inconsequential. SpaceX does research, and no matter how close it formerly was to Fastrak the Merlin currently isn't one.



Now, more interestingly, does anyone know what the wording for the mission-to-Mars earmark was? NPR made me wonder if NASA is supposed to do a cycler (I really want an automated Moon base to build habitat hulls for 4+ year Mars orbiters, but there's no way that could get off the ground as fast as conventional sourcing).

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Re: The "Real Aerospace" Thread

Post by Mjolnir »

icekatze wrote:hi hi

I got the numbers from Former ULA CEO Michael Gass, and the ULA's 2014 launch contract. 164 million is the cost for a low end Delta rocket, not a low end Atlas rocket.
No, it is the cost for an Atlas V 401, according to ULA's current president and CEO, figures he gave in testimony to Congress, and ULA's web site. And that's not even the cost of a separate launch, it's as part of the 36-launch block buy, and when the block buy was just 27 launches the it was $184 million for a 401...buying a single launch would cost much more.

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Re: The "Real Aerospace" Thread

Post by Nemo »

I still dont understand why we want to bother going to Mars in person anyway. Let the rovers go down in the gravy well. Use the people to man stations on the moon and start up some manner of resourcing and manufacturing capacity. Even that can be largely auto or tele-operated.

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Re: The "Real Aerospace" Thread

Post by Mjolnir »

Absalom wrote:
icekatze wrote:Not to mention the fact that the Merlin gets its excellent thrust to weight ratio at the expense of specific impulse.
As long as it can achieve orbital insertion of the payload, this is perfectly reasonable. You'll never get good Isp from a chemical rocket because pure chemical rockets just can't achieve the enery / mass ratios needed, so you're better off focusing on ion engines & such as soon as you get your orbital characteristics to a state that allows them to achieve the job. I won't say that higher Isp chemical rockets are inherently bad, but if that cuts into your reusability quotient (just as an example), then you need to ditch the extra Isp, because the rockets currently cost much more than the fuel, so if you cut rocket costs by half (which a single reuse of a lower stage probably won't quite achieve) then you might get around 40% cost reductions. Fuel, meanwhile, commonly costs ~10%. Thus, reusability is more important than Isp while your reuses are few (or none), because each reuse makes more of an impact.
If they were obsessing over such minor differences in Isp, they wouldn't be using a kerosene-burning gas-generator engine in the first place.

Also, increasing thrust to weight on a first stage engine reduces gravity losses. Given the limited delta-v required of the first stage, trading Isp for increased T/W can easily be a net gain. Any increase in thrust or reduction in engine mass on the first stage also translates directly into more mass available for the second stage and payload. As for the second stage, the Merlin 1D Vacuum gets a specific impulse of 348 s, considerably higher than the vacuum Isp of the Fastrac.

Absalom wrote:Now, more interestingly, does anyone know what the wording for the mission-to-Mars earmark was? NPR made me wonder if NASA is supposed to do a cycler (I really want an automated Moon base to build habitat hulls for 4+ year Mars orbiters, but there's no way that could get off the ground as fast as conventional sourcing).
What mission-to-Mars earmark? There's no manned Mars mission being funded, just the ExoMars lander and the 2020 rover.

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Re: The "Real Aerospace" Thread

Post by icekatze »

hi hi
As noted above, the block buy lowers the incremental lower end Atlas V launch costs to less than $100 million/
- The source Mjolnir cited.

It is important to note that the line item for the ULA contract includes maintenance and facilities for all of their rockets, including the larger more expensive Deltas, and that the original long term contract called for more launches but was scaled back. It is also important to note that the same budget line that gives the 164 million block launch cost also includes the funds that were spent on Space X's certification, among other things.

I wish I could get better information about the actual launch costs of various launch vehicles, prior to the addition of launch company profits. Unfortunately that information seems difficult to find.

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Re: The "Real Aerospace" Thread

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Nemo wrote:I still dont understand why we want to bother going to Mars in person anyway. Let the rovers go down in the gravy well. Use the people to man stations on the moon and start up some manner of resourcing and manufacturing capacity. Even that can be largely auto or tele-operated.
Because it's there.

More seriously we really should push to get a functioning, self-sufficient colony on a different planet. There's ALWAYS the possibility of an extinction level event happening here on Earth, whether it's super-volcano or asteroid strike. As a species we need to expand to ensure our own survival.

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Re: The "Real Aerospace" Thread

Post by Mjolnir »

icekatze wrote:hi hi
As noted above, the block buy lowers the incremental lower end Atlas V launch costs to less than $100 million/
- The source Mjolnir cited.

It is important to note that the line item for the ULA contract includes maintenance and facilities for all of their rockets, including the larger more expensive Deltas, and that the original long term contract called for more launches but was scaled back. It is also important to note that the same budget line that gives the 164 million block launch cost also includes the funds that were spent on Space X's certification, among other things.

I wish I could get better information about the actual launch costs of various launch vehicles, prior to the addition of launch company profits. Unfortunately that information seems difficult to find.
That was the incremental cost. That's not even the average cost (which is $225 million per launch for the block buy), it's only of interest if you are considering adding another launch to a $17.6 billion contract consisting of a 36-core, 28-launch block buy, 50-launch prior buy, and $6.9 billion for operations and infrastructure. There is precisely one customer who would do such a thing...and guess what, if you made that kind of guarantee to SpaceX, they could probably offer a better deal as well.

https://twitter.com/torybruno/status/584032353787326464

And even if $100 million was actually representative of the launch cost, it still wouldn't be anywhere close to the price you claimed.

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Re: The "Real Aerospace" Thread

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fredgiblet wrote:
Nemo wrote:I still dont understand why we want to bother going to Mars in person anyway. Let the rovers go down in the gravy well. Use the people to man stations on the moon and start up some manner of resourcing and manufacturing capacity. Even that can be largely auto or tele-operated.
Because it's there.

More seriously we really should push to get a functioning, self-sufficient colony on a different planet. There's ALWAYS the possibility of an extinction level event happening here on Earth, whether it's super-volcano or asteroid strike. As a species we need to expand to ensure our own survival.
The biggest threat is ourselves. It needn't even be something as dramatic as a war or plague, a bad enough economic crash might destroy our capability to maintain a high-tech civilization, with recovery being difficult or impossible due to all the easily-accessed resources being long gone. Just losing space capability means losing weather satellites, with massive impacts to agriculture and shipping. A small self-sufficient off-planet industrial base capable of producing moderately sophisticated electronics for weather and comm satellites would make a huge difference in our ability to recover.

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Re: The "Real Aerospace" Thread

Post by icekatze »

hi hi

The $225 million average cost is including the launches of Delta IV heavy rockets, which are significantly more expensive, and carry a significantly larger payload. (Not to mention, people have been wanting to retire the Delta IV, because they know it is old, but haven't been able to secure a replacement yet.) There is a lot of other expenditures that went into the long term contract that are not directly related to any individual launch's costs, but are still important.

The further down the rabbit hole I look into this, the more reasons I see why comparing the various launch costs with the aggregated pricing figures quoted by CEOs on all sides of the issue is not really increasing my understanding of the efforts involved. Although it has been someone informative to see how the requirement to have launch vehicles on standby for immediate use at any time increases maintenance costs.

Considering how much time I've spent trying to dig into this, I think I'm just going to have to leave it, and watch how things unfold. Space X might succeed, they might not, and there are some pretty competent minds predicting one, the other, and everything in-between.

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Re: The "Real Aerospace" Thread

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Mjolnir wrote:
Absalom wrote:Now, more interestingly, does anyone know what the wording for the mission-to-Mars earmark was? NPR made me wonder if NASA is supposed to do a cycler (I really want an automated Moon base to build habitat hulls for 4+ year Mars orbiters, but there's no way that could get off the ground as fast as conventional sourcing).
What mission-to-Mars earmark? There's no manned Mars mission being funded, just the ExoMars lander and the 2020 rover.
Is that based off the 2015 budget, or the 2016 budget that added ~1 billion to NASA's funding? I wasn't able to catch most of what was said at the time for some reason, and looks like I misunderstood what was being funded.
fredgiblet wrote:
Nemo wrote:I still dont understand why we want to bother going to Mars in person anyway. Let the rovers go down in the gravy well. Use the people to man stations on the moon and start up some manner of resourcing and manufacturing capacity. Even that can be largely auto or tele-operated.
Because it's there.

More seriously we really should push to get a functioning, self-sufficient colony on a different planet. There's ALWAYS the possibility of an extinction level event happening here on Earth, whether it's super-volcano or asteroid strike. As a species we need to expand to ensure our own survival.
I question whether it should be so specific as a planet (there are proposals for O'Neill cylinders & such, after all, and shorter-term for "dumbell" stations), but yes.
icekatze wrote:Although it has been someone informative to see how the requirement to have launch vehicles on standby for immediate use at any time increases maintenance costs.
And this is why ICBMs use solid fuels (stability is measurable in decades), and the Ares 1 should eventually be resurrected in some form for quick launches of "life boats".

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Re: The "Real Aerospace" Thread

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Absalom wrote:I question whether it should be so specific as a planet (there are proposals for O'Neill cylinders & such, after all, and shorter-term for "dumbell" stations), but yes.
Sure, but can those serve long-term on their own? You need to have the ability to acquire natural resources and produce spare parts. Hard to do floating in space.

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Re: The "Real Aerospace" Thread

Post by Absalom »

fredgiblet wrote:
Absalom wrote:I question whether it should be so specific as a planet (there are proposals for O'Neill cylinders & such, after all, and shorter-term for "dumbell" stations), but yes.
Sure, but can those serve long-term on their own? You need to have the ability to acquire natural resources and produce spare parts. Hard to do floating in space.
The difficulty of sourcing materials in space is tied to distance (mostly distance to volatiles such as bulk hydrogen, phosphorus, & other such (though if you succeed in building cloud facilities on Venus, then hydrogen, sulfur, and nitrogen should be covered)), and zero-gee. The reason I think we should mine the Moon first is so that the materials thusly sourced can be used to build a mining unit large enough to handle small asteroids. The simplest possibility I can think of is a big aluminum bag and an overpowered laser: the laser fires on the asteroid, material vaporizes & condenses on the bag, when enough has been condensed the bag is cut into pieces & reprocessed. This might be doable without lunar materials, but I doubt that any other industrial-size processes would be, and the bag method could prove rather slow.

Refining is not precisely identical to the same thing on Earth, but the asteroids are actually already semi-differentiated, and even if they weren't it would just be an issue of storing the stuff that wasn't immediately needed. Not a big deal, especially considering that:
1) most of the extra will probably be non-volatile materials we would want to use in bulk anyways, such as aluminum & silicon,
2) not only is sunlight 4x as strong directly outside the Earth's atmosphere as it is at sea level, but zero-gee allows comically flimsy mirrors to work well, so energy is not the issue in space that it is on Earth.
Sodium & potassium (to refine oxidized materials) are more of a concern than almost anything else.

As for producing parts, just use the same processes in space as you would on Earth. If you have a lot of fragile parts that are subjected to huge stresses, then you've done something wrong, because most of the stresses should be taken up by multi-hull pressure hulls, with few moving parts (the only moving parts subjected to high stress should be airlocks, honestly). There's little to no need for high weight efficiencies, and if you try for it in a space-born bulk habitat or infrastructure project, it just demonstrates a lack of consideration for safety margins. The high-mass-efficiency designs we commonly associate with space are honestly mostly built like that due to the need to launch them: when the materials are already most of the way out of a gravity well, we aren't trying to get things around fast, and solar sails are available for maneuvering, design priorities are less inclined towards balsa-wood hulls barely thick enough to withstand a light breeze, and more inclined towards steel or titanium hulls sufficient to withstand a hurricane.

Or were you thinking in terms of projects not occurring outside the station hulls? Because that would be like cities without any of the projects (farming, mining, etc.) that support them: lacking in a foundation, and thus doomed by mismanagement.

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Re: The "Real Aerospace" Thread

Post by fredgiblet »

Mining asteroids isn't as simple as most sci-fi would have you believe, just finding and getting to them is gonna be a pain in the ass. You're going to burn a LOT of fuel getting there and back in a reasonable timeframe.

Getting natural resources is significantly more difficult in space than on a planet, expanding is more difficult and expensive in space than on a planet, keeping healthy is more difficult in space than on a planet. The only thing that I see as better about space-born living would be short-term setup, it would probably be faster to get a functional colony set up in a space habitat than on Mars.

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Re: The "Real Aerospace" Thread

Post by Nemo »

Asteroid mining can be long term replenishment as metals on the moon become more difficult to acquire. Use small efficient engines or sails and aim them at the moon with a designated impact zone for a given time frame. Mostly its a matter of getting as much of the mass and material you need for any endeavor already out of the gravy. Until you have that capacity, talk of colonizing other planets is just Disney style wishful thinking.

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