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@tater whoah... I had no idea they’d gotten that far along in the testing regime. That thing had so much promise, thrown under the bus. Now I’m sad. :(

@sevenperforce and yet we sort of just saw it in the video linked

 

(Relevant to this thread bit): how did they make the flip? Engine gimbal alone or were there flight surfaces?

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55 minutes ago, sevenperforce said:

Does anyone have a table comparing staging velocities for expendable F9 to staging velocities for RTLS F9 and ASDS F9? With that sort of data, I could build a very solid model for F9 performance to almost any destination in any configuration.

http://silverbirdastronautics.com/LVperform.html

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57 minutes ago, sevenperforce said:

Does anyone have a table comparing staging velocities for expendable F9 to staging velocities for RTLS F9 and ASDS F9? With that sort of data, I could build a very solid model for F9 performance to almost any destination in any configuration.

No table, but I've watched a bunch of F9 launches. RTLS launches generally stage at 6,000 km/h. ASDS launches (typically used when the payload is going to GTO) stage at 8,000 km/h. During the FH launch on Tuesday, the center core separated from the upper stage around 9,500 km/h.

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1 hour ago, sevenperforce said:

Does anyone have a table comparing staging velocities for expendable F9 to staging velocities for RTLS F9 and ASDS F9? With that sort of data, I could build a very solid model for F9 performance to almost any destination in any configuration.

xaisqxao5ef01.png

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21 minutes ago, DAL59 said:

I've used that a lot, but the actual quoted/advertised/observed vehicle performance is more reliable. SilverBird makes too many assumptions about ascent, especially when we are dealing with altered trajectories for RTLS or ASDS. The only thing that matters to the upper stage is staging velocity.

17 minutes ago, Norcalplanner said:

No table, but I've watched a bunch of F9 launches. RTLS launches generally stage at 6,000 km/h. ASDS launches (typically used when the payload is going to GTO) stage at 8,000 km/h. During the FH launch on Tuesday, the center core separated from the upper stage around 9,500 km/h.

The FH was a sandbag; I don't judge it as very useful for establishing anything, especially since the payload mass is unknown.

But those staging velocities are very useful. Helps answer questions about BLEO performance.

13 minutes ago, Hesp said:

xaisqxao5ef01.png

Awesome!

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1 hour ago, softweir said:

A lot of good points. However, I feel I ought to point out that there has been a revolution in automation which has made SpaceX landings possible: Lossless Convexification of Nonconvex Control Bound. You can read about the technique SpaceX use HERE.

The paper was in 2013 almost 2014. By that time SpaceX had already worked out most of their landing bugs. See below the only major bug left was grid-fin engineering. 

https://en.wikipedia.org/wiki/List_of_Falcon_9_and_Falcon_Heavy_launches

This you will find relevant although not the only evidence that the engineering constraints (the structure, not electronics) needed to be improved before reproducible landings could be accomplished.

Quote

Following second-stage separation, SpaceX performed a test flight, which attempted to return the first stage of the Falcon 9 through the atmosphere and land it on an approximately 90-by-50-meter (300 ft × 160 ft) floating platform—called the autonomous spaceport drone ship. Many of the test objectives were achieved, including precision control of the rocket's descent to land on the platform at a specific point in the Atlantic ocean, and a large amount of test data was obtained from the first use of grid-fin control surfaces used for more precise reentry positioning. The grid-fin control system ran out of hydraulic fluid a minute before landing, and the landing itself resulted in a crash.[97][98] -wilipedia

If prediction is any measure of which metric they are using, my bets are that B5 performance testing is not anywhere near finished . . .while BFR may shorten this process, also are on the testing to improve both the B5 F9 markedly and  FH PL>LEO to at least 80 kT maybe 100 kT. The hangup in the performance of FH was the visible failure of the core landing. The initial burnback is as if they were still using f9 burnback protocols, indicating at least these have not been tweeked. Which means there is still performance left in core to be had. Im not criticizing them, but once B5 is fully operational I expect you are going to see many small design improvements that give tiny boosts in performance.

 

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16 hours ago, Northstar1989 said:

Just found time and energy to watch the launch (working as an EMT is demanding!)  Very cool!

Now they've just gotta start looking at more things they can do with all that payload.  Developing a system of Propulsive Fluid Accumulators and orbital fuel depots would make it possible to refuel the upper stage in orbit (by launching it with surplus kerosene and getting LOX from the PFA's) to enable upper stage recovery, and go a long way towards bringing down the cost of interplanetary space travel by allowing mission designers to leverage the fuel mass they bring to Low Earth Orbit (so 1 ton of Kerosene becomes as good as more than 3 tons of Kero/LOX in Low Earth Orbit, as Kero/LOX is more than 2/3rd's Oxygen by mass...) for instance...

https://en.m.wikipedia.org/wiki/Propulsive_fluid_accumulator

 

The problem is the specific kinetic (µ/2r)  that you have and the lack of specific energy that your particle of interest have (random). The principle scattering force for particles is UV from the sun and the scattering wavelength is very low for hydrogen and a minor constituent for sunlight, particles scattered by UV don't generally have enough momentum to escape and to your prograde motion the direction of scattering  non-rotating reference frame randomize. This is a problem for Venus and Mars because of lack of magnetic field allows particles to penetrate the atmosphere and scatter gas, mainly protons out of the atmosphere. This is not the case on Earth we have van Allen belts, and over the whole of Earths spatial atmosphere only about a kg is lost per day. There is simply not enough energy to scatter significant amounts oxygen above a certain altitude.

1. You have a very strong vacuum pump and you vacuum space. You would pick up particles if the nozzle is pointed in the direction of travel otherwise no particles, you could put a styofoam cup were the nozzle was and you would probably capture the same amount of hydrogen, there simply is not enough delta-pressure in space to make a vacuum pump useful.

2. So alright you dangle a gigantic cup behind the space craft (a giant plastic cup with a tiny vacuum pump at the vortex)[The spacecraft rotates 1 per orbit so that the cup is always behind the craft). The average velocity of the particles hitting the cup is 7840 m/s, your craft in merging with the particle gets all their momentum. If we replace moment of intertia with momentum (assuming a right handed orbit) then -7840*mass of particles vacuum. So suppose you vacuum hydrogen and oxygen from space at 7840. . .in order to maintain orbit, bad news, the Exhaust velocity is 4740 m/s with burning you just lost 3000 dV per particle. But its actually much worse, because you would have to capture 100s of hydrogens before capturing one oxygen.

3. Ok so you only expand your cup when the craft is passing the angle to prograde of 180 (in the direction of sunlight flow) and collect charged slow moving hydrogen that are moving 1000s of m/s . . . .a good choice but the problem is that there is not enough pressure and UV from the sun to charge all of the hydrogen you pass, volume swept is much much lower.

4. So to compensate you build an ION drive, lets make it real, its needs 16,000 exhaust velocity to neutralize all forms of drag created. (ISP = 16000). OK so now you have to haul Xe or Ar from Earth and the mass of a large number of solar panels (which also create drag) to compensate for the fuel, so now you are paying money to send fuel to space.

And alternative to making a big plastic cup to capture O2 is to make your ship very space-aerodynamic (gently deflecting particles and using some very aerodynamically shape mass accelerating magnets and the solar panels to accelerate the particles in the other direction. You could use UV to ionize the gas prior to reaching the ship capture electrons, then push off on the gas, and electron emit retrograde. In this scheme you use the same number of particles, but instead of trying to capture them and loose the dV you hurl them into another direction (say an unfriendly spacecraft you want to deorbit). The problem with this is your solar panels that make the electricity for you hadron collider creates alot of drag itself . . . .

SpaceX does have the right Idea, the key however to getting more fuel into space is to make launches more cheaply and then more efficient at roughly the same cost. Instead of putting solar panels in space to make lots of drag and try to devinate hydrogen and oxygen into existence . . . . . . . better idea is cheaper more efficient solar panels . . . .more efficient hydrolysis. . . . . .RS68A like engines are already great, something like that smaller and you have all kind of thrust you need to increase payload. Even if hydrogen it too much of a hassle on the ground, its not too incredibly difficult to make Methane from H2 and CO2 or to use the electricity-photosynthesis to make ethanol, acid dehydrate it to ether (35'C) or hydrogenate it to ethane (-88.5'C).

The point is cost, get cost down and we go to space, keep cost high, no matter how efficient the process and we stay on the ground. Its not particularly ecofriendly idea (that CH4 is a greenhouse gas), but spending 20 billion dollars to get one really efficient rocket into space has alot of unseen ecological unfriendliness associated with. Seriously SpaceX can put solar panels on the roofs of all their facilities and have a more beneficial environmental impact relative to any scheme designed to scoop fuels from space.

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16 hours ago, sevenperforce said:

Falcon Heavy can do moon missions easily enough but it's not going to get us on our way to Mars.

The Orion- which was supposed to be capable of going to Mars with an extended habitation module- is supposed to slate in at 10.4 metric tons for the capsule alone.

https://en.m.wikipedia.org/wiki/Orion_(spacecraft)

The EAM proposed by Orbital AKT is basically just a modified Cygnus.  The 2-segment one is slated to be able to support 4 crew for 60 days on its own, the 4-segment one would probably be at least twice as capable...

https://en.m.wikipedia.org/wiki/Cygnus_(spacecraft)

http://www.spaceflightinsider.com/missions/commercial/orbital-proposes-future-deep-space-applications-cygnus/

The "standard Cygnus" in cargo configuration with a 2 ton payload capacity only masses in at 1.5 metric tons.  The "enhanced" version with 3.2 to 3.5 tons of payload capacity only masses in at 1.8 tons (so there is a less-than-linear relation between size and dry mass).  A modified version for crew probably would weigh 5-6 tons for the 4-segment manned version at most... (that's likely more than a 100% increase in mass vs. a cargo version with the same dimensions)

A Falcon Heavy can lift 63.8 metric tons to LEO in a single launch.

https://en.m.wikipedia.org/wiki/Falcon_Heavy

So, you could easily piece together a "flag and footprints" Mars mission by launching something like an Orion Capsule (10.4 tons), a few 4-segment EAM's based on the Cygnus (5-6 tons each), and a Mars lander (probably not more than 40 tons dry mass) on 4 or 5 Falcon Heavy launches- with plenty of extra mass budget to work with for the transfer-stages...

With a little orbital-docking, and perhaps staging the components in a highly-elliptical orbit before the astronauts even arrive, it should be perfectly possible to carry out a flag-and-footprints style Mars mission with the Falcon Heavy as the launch vehicle.  It's capable of launching any individual component necessary for a Mars mission- it's just a matter of finding ways to hook them all together in Earth Orbit (propellant-transfer between the payloads also would help here...)

BFR is nice, but it's only really necessary for Mars colonization or long-term stays- not for simple "flag-and-footprints" missions similar to Apollo but on Mars...

And at $450 million for five Falcon Heavy launches (going by SpaceX's estimated price tag, of $90 million per Falcon Heavy launch) you could launch the components for TWO Mars missions for less than the cost of a single Saturn V... (which would also help with redundancy- send two missions at once to different parts of Mars and they can potentially provide assistance to each other if one gets in trouble...)  Each Falcon Heavy has a bit more than half the payload capacity of the Saturn V, but only costs less than 10% as much...

Edited by Northstar1989
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13 hours ago, tater said:

You can see RCS puffs on DC-X.

Delta Clipper was pretty cool. BFS is really the grandchild of A few of Phil Bono's designs from the 1960s, and the child of DC-X.

Actually, one could argue that the heritage of DC-X is New Glenn, because many of the ex-McDonnell-Douglas team who worked on Delta Clipper ended up at Blue Origin.

23 minutes ago, Northstar1989 said:

So, you could easily piece together a "flag and footprints" Mars mission by launching something like an Orion Capsule (10.4 tons), a few 4-segment EAM's based on the Cygnus (5-6 tons each), and a Mars lander (probably not more than 40 tons dry mass) on 4 or 5 Falcon Heavy launches- with plenty of extra mass budget to work with for the transfer-stages...

That word "easily", it doesn't mean what you think it means.

There is nothing "easy" about assembling space hardware like Lego. Ask SpaceX about FH. Ask LM about SLS.

 

 

Edited by Nibb31
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4 hours ago, Nibb31 said:

There is nothing "easy" about assembling space hardware like Lego. Ask SpaceX about FH. Ask LM about SLS.

Particularly since the STS are NOW sitting in cushy museums and theme parks.:wink:

Edited by PB666
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@Nibb31, meerly seeing something done by others is a huge thing, as you know it is then possible. Look at the Chinese spacex knock off in progress (they’re flying a grasshopper now, and their planned rocket looks as much like Falcon as Buran looks like Shuttle).

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36 minutes ago, tater said:

@Nibb31, meerly seeing something done by others is a huge thing, as you know it is then possible. Look at the Chinese spacex knock off in progress (they’re flying a grasshopper now, and their planned rocket looks as much like Falcon as Buran looks like Shuttle).

https://en.wikipedia.org/wiki/Grasshopper_(rocket)

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48 minutes ago, tater said:

 

The first west coast sooty was Iridium-NEXT launch three, of Giant Space Jellyfish fame.

11 hours ago, insert_name said:

SpaceX says that the govsat stage broke up on it's own, not by an airstrike

https://www.cnet.com/news/spacex-denies-air-force-bombed-falcon-9-govsat-1-atlantic/

I thought that was fishy.

No pun intended.

7 hours ago, Northstar1989 said:

The Orion- which was supposed to be capable of going to Mars with an extended habitation module- is supposed to slate in at 10.4 metric tons for the capsule alone.

The EAM proposed by Orbital AKT is basically just a modified Cygnus.  The 2-segment one is slated to be able to support 4 crew for 60 days on its own, the 4-segment one would probably be at least twice as capable...

The "standard Cygnus" in cargo configuration with a 2 ton payload capacity only masses in at 1.5 metric tons.  The "enhanced" version with 3.2 to 3.5 tons of payload capacity only masses in at 1.8 tons (so there is a less-than-linear relation between size and dry mass).  A modified version for crew probably would weigh 5-6 tons for the 4-segment manned version at most... (that's likely more than a 100% increase in mass vs. a cargo version with the same dimensions)

A Falcon Heavy can lift 63.8 metric tons to LEO in a single launch.

So, you could easily piece together a "flag and footprints" Mars mission by launching something like an Orion Capsule (10.4 tons), a few 4-segment EAM's based on the Cygnus (5-6 tons each), and a Mars lander (probably not more than 40 tons dry mass) on 4 or 5 Falcon Heavy launches- with plenty of extra mass budget to work with for the transfer-stages...

First of all, Falcon Heavy cannot presently lift 60+ tonnes to LEO. It is volume-limited and the PAF is mass-limited. The upper stage would need a full redesign.

But what I meant, for starters, was using Falcon Heavy to actually send something on the way to Mars. If a fully-expendable Falcon Heavy was used to launch nothing but an International Docking Adapter, it would reach orbit with a nice healthy 97.1 tonnes of propellant remaining (the center core would be 330 m/s short of orbit at MECO, btw). If that upper stage were then to be mated using the IDA system to a Mars-ready stack, it could send up to 21 tonnes on TLI.

Not nearly enough for a landing.

Rockets are not legos, despite what my Roads to Duna challenge suggested. Assembling a higher-energy transfer stage using Falcon Heavy is really well outside the boundaries of what we are able to do right now. The IDA approach is the closest we can do to orbital assembly at this point. Propellant transfer is right out.

Orion was intended to be "Mars-capable" only in the sense that it was supposed to go along as the Earth entry vehicle. Anything Orion can do, Dragon 2 can do, apart from propulsion. More importantly, we have no landing or ascent vehicles.

7 hours ago, Northstar1989 said:

BFR is nice, but it's only really necessary for Mars colonization or long-term stays- not for simple "flag-and-footprints" missions similar to Apollo but on Mars...

And at $450 million for five Falcon Heavy launches (going by SpaceX's estimated price tag, of $90 million per Falcon Heavy launch) you could launch the components for TWO Mars missions for less than the cost of a single Saturn V... (which would also help with redundancy- send two missions at once to different parts of Mars and they can potentially provide assistance to each other if one gets in trouble...)  Each Falcon Heavy has a bit more than half the payload capacity of the Saturn V, but only costs less than 10% as much...

The sticker price for FH assumes booster recovery.

2 hours ago, tater said:

@Nibb31, meerly seeing something done by others is a huge thing, as you know it is then possible. Look at the Chinese spacex knock off in progress (they’re flying a grasshopper now, and their planned rocket looks as much like Falcon as Buran looks like Shuttle).

Buran looked like the Shuttle more for reasons of necessity than anything else. I suspect the same is true with the Chinese Falcon knockoff.

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Also, random...

If SpaceX really wanted to go all-up on an expendable Falcon Heavy launch for a very large LEO payload, they could conceivably deliver MORE to orbit by losing the upper stage altogether and mating the payload directly to the core interstage. Despite the core's lower ISP, you'd still be looking at 75-90 tonnes of payload.

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2 hours ago, sevenperforce said:

Well, yes. But logistically, it's really too much.

How many launch pads are they going to have at boca chica?
 

I should add . . . . . how do  they intend to cycling between F9B5 and FH at 39A, even that could present problems in the logistics. The correct point to judge this is when they can demonstrate the promised turn-around times on launches for F9.

Edited by PB666
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