kunok
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Posts posted by kunok
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We need a "deep space" habitat before doing interplanetary travel. Cislunar space is far outside the magnetosphere, it checks.
We need a substitute of the ISS, it also checks
It makes a lot of more sense than you think, the part that doesn't make sense is the mars trip, but that hasn't sense anyway with the current budget. I'm sorry to say that any plan for a mars trip is just plain unrealistic without a big increase in budget, the rocket is the smaller of the problems.
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On 22/3/2017 at 4:55 PM, sevenperforce said:
Is the limiting factor in deep-throttling a pump-driven liquid-fueled rocket engine the pump, the chamber, or the nozzle? Or does it vary from system to system?
For example, Raptor can downthrottle to 40% of max rated thrust. Does the 40% minimum have to do with combustion instability in the chamber, or flow choking in the nozzle, or flow within the turbopump and preburner?
First, raptor still doesn't exist yet, so any characteristic of it isn't real.
What you are asking is very very complex, but IIRC the most determinant one given a nozzle was the injector type, how good it mixes and spreads both the oxidant and the fuel. My propulsion teacher was a specialist in solid rockets tho, so I may be wrong.
On 22/3/2017 at 1:58 PM, shynung said:Are common automobile gasoline suitable for engine regenerative cooling? I'm talking about piston engines, not rocket combustion chambers.
That's an engineering question, and yes is already done to some extent, next to the inlet valve you have some regenerative cooling, even if you don't want to. Remember that the mayor focus in automotive industry is to cut cost, to ridiculous extents, this would be very expensive to do properly.
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33 minutes ago, Lukaszenko said:
That's like saying it's not the gun that does the killing, it's the bullet. The point is, they're part of a system designed for a specific goal, and one is useless without the other.
You could change the suborbital capsule in the NS to a second stage with a payload of the same total mass. It won't be in a Falcon9 class but it would be in a Falcon 1 class, but reusable.
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1 hour ago, KerbalSaver said:
I'm not quite sure what you mean.
What they do with junk when the only option is the dragon? Return it to earth instead of burning in the atmosphere.
The interesting part is: how much of the mass that returns to earth is useful? and how much is just junk?
Remember that IIRC there wasn't a call about being able to return cargo in the commercial cargo program.
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8 minutes ago, Yobobhi said:
Do you seriously expect a company with no experience beyond LEO to develop something such as the ITS in a short time? NASA will get there first for sure, and do it much better.
Pss, is more like beyond GEO
And yes, basically is what fans expect, to develop a bigger than Apollo program in record time with less resources and forgetting every middle step in the way.
BTW I talked the other day with an ablative materials engineer (you will be surprised if you don't know that cork based ablatives are pretty good) and PICAX is an ablative material, is not really a reusable material, nor is proven that could withstand multiples reentries, is this kind of things that make people in industry to have very big doubts in SpaceX claims
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19 hours ago, Elthy said:
Why? SpaceX seems way ahead in most fields, while Blue Origin only has their New Shepard, which about equals the old grasshopper.
The grasshopper doesn't equal the New Shepard at all, the grasshopper only developed the control landing, the other is a full human grade suborbital rocket.
Blue Origin has a reusable from the start design, SpaceX has a cheap and easy to manufacture rocket design upgraded to be reusable.
In the mid-long term I think Blue origin will be cheaper, because the lower operations cost. Blue origin has already a proven reused suborbital rocket, they know the caveats, all the logistics needed and what to improve in the next design (it's also said that they hired engineers from the dc-x program, and remember that the dc-x was very focused in reduced maintenance and ground support) and they will probably design the New Glenn with this in mind.
The joke is that I don't like neither of them.
18 hours ago, magnemoe said:DC-X was an SSTO, it would fail no matter how well funded. You can not build an practical ssto with rocket engines. Skylon might work, same with beamed power, not rockets.
I didn't claimed that it would have been a successful SSTO, but it would have developed the technologies required to have a better rocket tech, and probably would have ended in a good reusable first stage in the 90's or the 00's. DC-X was more a tech and logistics demonstrator, than a real scale model.
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Just now, Elthy said:
We dont know the current procedure, but Elon Musk wants a rocket that can be reused like a plane. I would bet they are way close to that goal for the first stage than the spaceshuttle ever was...
The spaceshuttle was also planned that way, that doesn't mean that will be achievable.
Time will say, but I think that Blue origin will be far better than SpaceX in this, and that we wouldn't be discussing any of this if the DC-X were funded in the 90's.
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We are derailing but
Spoiler"SpaceX have never deliberately tried to mislead people, they (or whoever else it might be) are just using the fact that very few people actually read things properly these days. " @Steel
This is a contradiction, if you are using the fact that most people don't really read things, you are actually deliberately trying to mislead people.
PD: I don't know how to properly quote inside a spoiler
Anyway in the actual topic
1 hour ago, Elthy said:Isnt the biggest difference in reusability, that the shuttle was more or less reassembled each time they reused it?
Do we really know what is done to a future reused stage in SpaceX? How much is reassembled?
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2 hours ago, Steel said:
Privately-developed, not privately funded.
EDIT: no I'm still wrong. I think most people just misquote "first privately-developed liquid-fuel launch vehicle" as "first privately-developed launch vehicle"
That's what I was trying to say.
And I think that is very easy to misquote that wording, and I think is very naive to think that easy to misquote wording wasn't done in purpose. Nowadays most people believe that SpaceX had developed the first private orbital rocket ever.
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2 hours ago, mikegarrison said:
Yeah. But what is a first-stage rocket if not a rocket engine (or three) that ignites on the pad? I think it's nifty what SpaceX and Blue Origin are doing, but it's a very strange reinterpretation of history to claim that this will be the first reused orbital rocket stage....
It's also claimed that Falcon1 was the first privately funded rocket rocket to reach orbit, apparently Pegasus never existed.
Welcome to the posmodernism
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On 17/3/2017 at 7:00 AM, kerbiloid said:
Btw how would they send a repair team? Airplane can't, rocket can't. Only on lesser zeppelins. The docking of two zeppelines 40 km above the Earth would be a magnificent show.
The "idea" is to just land the zeppelin, and the atmosphere above the stratosphere IIRC is not that turbulent.
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Somewhat related:
What about a "big" telescope in a high altitude blimp? To overcome atmosphere extinction, overcome seeing and be able to see in wavelengths impossible in the surface, without the need to be in orbit and the capability to have maintenance be upgradeable.
It maybe is stupid, I'm very tired today.
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52 minutes ago, StrandedonEarth said:
Now they have a hat, he must be serious!
Clearly he also wants the team fortress 2 market
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Just now, Nothalogh said:
They built Grasshopper just to prove it was possible
That was for a defined goal, that is to develop the landing capabilities of the Falcon9. (And it was already proven what grasshopper did)
You are basically suggesting to design a new service module, that is exactly one thing that SpaceX has opposed to do. You are really oversimplifying the engineering in that.
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12 minutes ago, Nothalogh said:
Why not, it's a logical thing to test and prove possible
Because it's very expensive to design and build the hardware just to test that.
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Well now here goes a cynical note about SpaceX loosing their place as the rock star
SpoilerIf SpaceX looses it's place about being the coolest option out there because it starts loosing the "competition" in them own "cool" goals, they will also lose their source of "cheap and willing to do extra hours" workers, and that would be a big problem for the company.
I don't think it will happen tho.
2 minutes ago, tater said:The difference is that a sailor is actually steering the ship. Spacecraft are automated. If you are a passenger on Soyuz going to ISS and back, what makes you an "astronaut" other than being in space? Only one of the 3 docks the craft after all, the others are merely passengers, right?
For me not only the ones steering the ship are sailors. The scientists in a boat researching fish or whatever in the ocean are also sailors, the fishers that doesn't nothing in the navigation of the boat, the workers in a cruise, etc.
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33 minutes ago, tater said:
My stunt comment was really in response to the idea that somehow these "tourists" are not in fact "astronauts." Are mission specialists who are not pilots astronauts? Is "astronaut" only conferred upon people who work for a government agency, or people who have certain training? Would someone trained minimally for spaceflgith who is, say a physician be called an astronaut if his suit patch says "NASA," but somehow not an astronaut if his suit patch says "Blue Origin," or "SpaceX?"
A tourist in a cruise is not a sailor, the people working in it are, a passenger in a ferry is still just a passenger.
Why would be different with the astronauts? If you are working you are an astronaut, if you are making tourism, you are a space tourist, if you are a passenger you are "only" a passenger.
PD: At least in Spanish makes sense this way
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I think we also need an official distinction between principal moons and moonlets (or other name, that's not the problem). Something like Jupiter has 4 moons and at least 63 moonlets
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22 hours ago, monophonic said:
What? You seem to be trying to tell us how amazingly good SpaceX's marketing department is.
I'm an engineer I suffer the marketing and commercial department overpromising things.
(I don't currently have that kind of job but in the past...)
You develop a sixth sense for this kind of things
20 hours ago, Cuky said:Wasn't Dragon designed to be able to carry both cargo and crew before they decided to leave Dragon as a cargo only and instead develop Dragon v2? I mean, on SpaceX's youtube page some of the first animations regarding crew transport to the ISS are shown with Dragon docking to the ISS without use of canadarm
Yeah, that's true, they now have a cargo spacecraft that isn't really that modular, but that's not necessarily a problem, I suppose that have common manufacturing processes with the crew version, look at Progress and Soyuz (in the other hand Roscosmos have plans to change the Progress to something non soyuz based because it could be cheaper...).
But that's because the lack of mid/long term technical plans in SpaceX, nothing new.
20 hours ago, Cuky said:the most technically advanced launch escape system ever developed
And here you can see how they were overclaiming since at least 2012.
21 hours ago, wumpus said:Dragon is a fairly light payload for spacex. You may have noticed that the booster returned to land, something that never happens with a full load. Perhaps my "half a payload" was pretty inaccurate, but spacex certainly had more cargo room for that flight.
The Falcon have extra room, not really the Dragon, and because that they announce they can launch extra secondary payloads capacity so they could claim that the dragon has that cargo capacity. Falcon is pretty overpowered for this cargo.
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13 hours ago, sojourner said:
While the Dragon may be volume limited greater than weight limited, it does have one advantage over all of the other craft you mentioned. It can return cargo to Earth. Also, it's not "over promised" if the vehicle can actually do what is claimed. The only reason it hasn't is that NASA has yet to give it a cargo that meets the weight requirements at that volume.
NASA is the client, is SpaceX who needs to adapt to the NASA cargo not the other way, more when the dragon was designed to meet NASA's needs. Of course is overpromised, and also an unproven claim. And the capacity to return cargo IIRC wasn't a requisite
2 hours ago, Tullius said:let's not forget that it is mostly about the cost per kg to ISS
With is also higher that the cygnus.
Dragon is a good modular spacecraft, which probably make it worse than any specialized design for any given mission, but very versatile, just not as good like SpaceX marketing claims.
You could see how little I like marketing
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7 hours ago, kerbiloid said:
Of course, I like big badabooms (otherwise hadn't played KSP!), but yet afaik the only visible thing which is used as an evidence of this event in the far past are the Moon craters.
No, mercury also have craters of the same age, and there is more info out there. But today I'm sleepy and lazy, so I won't search for you.
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13 hours ago, kerbiloid said:
I'm sure, you're too optimistic. The angular momentum distribution looks too pretty to allow something big to exist somewhere far.
As this thinked to me, when the proto-Sun got ignited it had snarled the gas-n-dust disc with its electromagnetic field and sun storms, making this to stick up into one-two huge hydrogen-helium balls and giving them all Solar System momentum, previously stored in the protostar body. So, JupSat pair accumulated most of this angular momentum and got thrown away from the Sun.
The other planets are just gobs of scrap from that feast of life, they are spread along the JupSat path as droplets of fat, under Titius-Bode distribution.https://en.wikipedia.org/wiki/Five-planet_Nice_model#Notes_on_Planet_Nine There are models derived from the Nice model that could somewhat explain that planet
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Bro, what machine tools you have? You won't be able to do this with manual machine tools, and high temp alloys are a pain to machine even with very expensive tools.
And seriously you wont get high temp aloys from old trailers, and scrap, unless you have aircraft engines scrap, and that even being scrap is very expensive and valuable.And for safety, just put a mirror at 45º so you can see behind a corner, far from the test engine and in no direct line of the possible shrapnel
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5 hours ago, wumpus said:
In this case it is more like "customer paid for the whole rocket, but only brought half the payload". I'd hardly call falcon 9 overpowered, although I'd assume that falcon 5 was originally intended for this role (had they developed falcon 5, landing would be like landing a falcon 9 on three engines without the ability to cut two at the last second). I'd also assume that developing Falcon 5 would have similar costs to Falcon Heavy, which certainly wasn't all that cheap (and have nearly zero savings compared to a reused falcon 9).
Is just that the cargo capacity of the dragon advised by SpaceX, like in the picture posted by @tater, is not realistic. Useful things are usually a lot less denser that what dragon will allow in the little space it have. In this dragon it was only 2389kg, and only 1492kg are pressurized. That's less than half the announced payload.
Dragon in theory could have 3300 kg of pressurized cargo in 10m3 and the enhanced cygnus for a similar cargo capacity (3300kg using an Antares, 3500kg with an AtlasV) has 27m3, that's almost 3 times the space for the same cargo. The unpressurized extra cargo capacity of the Dragon is mostly unused and has never flown to more than half the advised capacity (and that time was because it was used to send the bigelow beam module), but the cygnus has already flown at full capacity. We could also compare with the now retired ATV that had 48m3 for pressurized cargo or the good old Progress, both have the capacity to deliver propellant, and both have flown at full announced capacity. I will admit that I have little knowledge of the HTV, but looks like it also was launched with it theoretical full cargo capacity.Dragon is a good cargo spacecraft, with it's limitations, but please, stop repeating the over-promising claims of SpaceX
(I don't currently have that kind of job but in the past...)
European Space Industry and the future
in Science & Spaceflight
Posted · Edited by kunok
In this post I use we as the Europeans citizens
Your 2) point is precisely the job of an engineer. I worked only doing the 1) and 4) , and trust me, when things go wrong is a lot worse, and with the years "the nobody knows why this component was selected instead of this other" is terrible.
WUT? I'm nowadays working for a space startup, with politicians involved, and there is lots of them.
Can I suggest that you have a very biased view of what is a life changing achievement? In the practice nothing has changed since the apparition of SpaceX, only a cheaper orbit delivery service, and that's only a money problem, it isn't changing anything in any other aspect, even the dragon is redundant with other manned spacecrafts. How is that more life changing that Rosetta and Philae? What about Mars and Venus express? What about the Sentinel program?
Have you read about the internal organization of SpaceX? Because you may be surprised.
One thing that we should start is stopping spreading the SpaceX's propaganda, and remarking only ours failures, that is exactly what you did (no offense intended), your post is exactly an example of the problem. But I think that this week this would be impossible.
This is simply not true. Even if reusing Falcon9 is really profitable, thing still not guaranteed, we need to have rockets, we can't depend of how good we are with usa, russia, or whatever. We have enough problems with the Soyuz.
And Arianne 5 is probably the most advanced and most reliable rocket currently, with lots of developments. If we ever do the Arianne 6 or Arianespace rocket reusable it will be better than the Falcon9 because we have better tech, SpaceX is not developing new techs only improving the transferred techs of NASA. We have currently re utilization programs http://www.pldspace.com/blog/en/2016/11/07/pld-space-esa-support-reusable-launch-vehicle-europe/. And this is again a startup with public investment.