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Advanced Concepts / Re: Space Elevator for Mars
« Last post by LMT on Today at 02:44 AM »
You are the one who seems to be confused.

you apparently don't understand the most basic of equations governing rockets, and that you refuse to even do basic research on your own

Anyone calculating Omaha Trail efficiencies would use the rocket equation repeatedly, with gravity losses where appropriate, as we did. 

You might have asked, nicely.

Dr. Lades understands and appreciates that work, and all our work.  Hence his ongoing collaboration.  --  You're not going to accuse an ISEC Director of being confused etc... are you?  If not, you've reached the end of that mess.  You should just apologize for the misunderstanding.

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Quote
even if you aren't necessarily the world leader in space launch yet

2017:
Atlas V = 6 launches
Arine 5 = 5 launches, 1 planned
Falcon 9 = 16 launches and counting
Falcon  = Zero planetary / cislunar / large NSS missions
Atlas/Ariane = most planetary / cislunar / large NSS missions.

If you can't do them, you're not a leader. Cherry picking payloads only works for so long.

Sure they can.  It's just that the dominance in commercial launches is simply the first "symptom".  Obviously planetary launches lag, but give it a couple of years and you could do the same comparison with those as well.

You can also make the point that SpaceX has yet to launch people.  And give it a few more years, and there's going to be very little left to compare even on that field.
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So no more ALT tests, or TBD?
None planned, next stop space! 8)
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An electric starter/generator could be used for electric gimbaling or electric grid fin actuation. I have a hard time believing they'll stick with open hydraulics for bfr/bfs
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I'm not sure about the cycle.

In a jet engine, you have a clear "cycle", since the far field inlet and outlet conditions are sinked into the same atmosphere, and mechanical power extracted from the exhaust goes into compressing the inflow.

Here, the conditions in the far field inlet are simple the tanks (with head pressure), and the outlet goes into the combustion chamber.   Mechanical power extracted from the exhaust goes into pumping the combustion chamber - not into the powerpack.

If you include the combustion chamber, then far field outlet conditions are the cold hard cynical vacuum of space.

If there's no cycle, then in theory you could just "light it up", but as you say, practicalities may dictate that the spin up will be impractically slow.

Whichever way, I don't think it's an intractable problem. For all that I know, they might put an electrical motor on the shaft...

- I'm sure of the cycles both gas generator and pre-burners.

- Before starting, the main chamber is at what ever the outside pressure is (which could be vacuum).

- Mechanical power extracted from a gas generator's or pre-burner's exhaust all goes into pumping the propellants!

- The propellants then either go to the main chamber or gas generator / pre-burner for combustion.
 In a gas generator cycle only a small portion of the propellants is burnt and it is exhausted separately from the main chamber. In a pre-burner a larger portion of the propellant is burnt and it is exhausted into the main chamber. The pre-burner obviously needs to be at pressure higher than the main chamber.

- No electric motors. Pumps for large rocket engines require 10s of thousands of horse power.

John
Depends where you draw the boundary of the control space.

If around the powerpack, then no, power doesn't go to pump propellant into it.  It is fed by head pressure.  Power goes into pumping into the main chamber.

If around the whole motor, then yes, but then a rocket engine as a whole - does it run a thermo cycle?  I'm not sure.  It's very different from a jet engine...

Anyway, yes, electric motors would have to be huge or only act as primers of some sort...  and they would have been visible in the CAD models.
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For all that I know, they might put an electrical motor on the shaft...

That was the idea I had and didn't voice because of the danger of baseless speculation. Once running, the motor would generate electricity to heat up and gasify some of the propellant in the tanks to create the autogenous pressure. Safes the running of hot fuel pipes in favor of electrical cables. No idea what is lighter but it probably would safe a lot of headaches with the hot pure oxygen.

Again, total speculation on my part and probably wrong.
Saying something is possible or even a good idea is not speculation...

Saying something "might be in place", or "may have happened" is.

So wrt electric drive, it'll be heavier than a gas starter, but much more reliable and controllable.

I have no doubt it was on the trade table, but who knows what they ended up with.
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Falcon  = Zero planetary / cislunar / large NSS missions
Atlas/Ariane = most planetary / cislunar / large NSS missions.
If you can't do them, you're not a leader. Cherry picking payloads only works for so long.

If you widen out from 2017, F9 did launch DSCOVR.
https://epic.gsfc.nasa.gov/archive/natural/2017/11/20/jpg/epic_1b_20171120054200.jpg

And - well - heavy, RSN.
So we're straining at gnats again. A 0.6 mT sat at earth's L1 point. Whee!

How soon do you think an FH is going to be lobbing deep space payloads, or a major NSS? It isn't RSN.

I'll bet you a cup of coffee that the first significant FH launch (and first significant non GTO payload) will be a Dragon capsule. And it won't be under a fairing  ::)

How many planetary missions? Zero. You do know that Centaur has a few notches worked up over quite a few decades. Flying incredible missions for longer than many here have been alive.

Things are changing. But try to keep a tiny bit of rational perspective while it does, OK?
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Great article. I had no clue they were doing Dream Chaser work at MAF.

Lockheed Martin is building the next Dream Chaser composite structure at the Michoud Assembly Facility (MAF).  Here is the press release:

Sierra Nevada Corporation and Lockheed Martin Expand Dream Chaser Orbital Vehicle Manufacturing
Very cool thanks! Glad there will be additional uses of the MAF facilities.

Sent from my SAMSUNG-SM-G935A using Tapatalk

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Great article. I had no clue they were doing Dream Chaser work at MAF.

Lockheed Martin is building the next Dream Chaser composite structure at the Michoud Assembly Facility (MAF).  Here is the press release:

Sierra Nevada Corporation and Lockheed Martin Expand Dream Chaser Orbital Vehicle Manufacturing
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