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Ever since Musk's Australian talk, very little has been said about Falcon Heavy and it's long term future. The focus moving forward all seems to be on the latest iteration of the BFR. We have yet to see a test flight of the highly touted Falcon Heavy, and the late 2017 launch seems to have slipped into December from an earlier Musk statement "as early as November." Is this related to the SpaceX launch manifest, launch pad availability, or just a hesitancy towards risk of failure? There were rumors circulated that NASA didn't want to risk LC 39A due to it's "historic significance," but could LC 40 not be ready to resume launch operations after the September 2016 explosion and fire. I'm at a loss to figure out what's happening.
Last edited by Oldfart1939 (2017-10-17 20:19:14)
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They're still planning to launch it, but I do wonder whether Musk has sort of lost interest in it because the BFR will be along in a few years and the Falcon 9 has a pretty robust payload capacity, and the Heavy is proving much more expensive to develop than they thought.
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Speaking as a skeptic, the BFR is actually more years away than Elon so optimistically states. GW has figured a factor of 2.5 time the years stated by SpaceX. They really need to go through the Falcon Heavy development stages and get more experience with larger rockets through the teething problems.
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Didn't NASA go from fairly modest sized Saturn to the huge one in one giant leap for spacekind?
It seems to me that there have already made good progress - the propellant tank prototype is done is it not? They have mastered the principles of propulsive landing, albeit on a smaller scale and the Raptor engine is well along the road of development. They presumably now understand huge amounts about mission control monitoring systems, building the body of the rocket, compartmentalisation and so on. If NASA could go from drawing board to finished article in 3 years with far less sophisticated tools at their disposal (e.g. no CAD at all as far as I understand in the early 60s), then why can't Space X?
They start building the rocket in 2018 according to Musk. Completion late 2019? First test 2020. Two more orbital tests early 2021. Mars simulation flight to Moon late 2021. Double Mars cargo launch 2022.
Speaking as a skeptic, the BFR is actually more years away than Elon so optimistically states. GW has figured a factor of 2.5 time the years stated by SpaceX. They really need to go through the Falcon Heavy development stages and get more experience with larger rockets through the teething problems.
Let's Go to Mars...Google on: Fast Track to Mars blogspot.com
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Spacex is contractually obligated to fly its Falcon-Heavy multiple times. The DOD contract it has requires that. If you look at the interval required to get -Heavy off the ground, it is about factor 2 longer than anticipated, since it was first supposed to fly in 2014, not late 2017 or early 2018. The delay is typical, because things in the launch business quite typically turn out to be be harder-than-expected. That's just Murphy's Law in action. It is to be expected, at least by those with real experience. Musk's team understands this now, even if he himself really doesn't.
That being said, I think -Heavy will give them the intermediate step they need to get from Falcon-9 to BFR. -Heavy will give them the experience they need running engine counts on the order of 25 to 30. It is about the same payload ratio to -9 as was Saturn-5 to Saturn-1: about 3 to 1.
Engine count is the main difference between BFR and -9, the others being the larger Raptor engine, and switching to liquid methane instead of kerosene as fuel. Of those, high engine count is the "biggie", that being what stopped the Russian N-1 decades ago.
Once Spacex is past the high engine count with -Heavy, then BFR does not look like such a big step from -Heavy, the payload ratio being that same factor of 3 as a step.
So it looks to me like they really are doing the essential intermediate experience steps getting to BFR, and it really is -Heavy that is the appropriate intermediate step.
The one that worries me is the ITS second stage, not the BFR first stage, which is nothing but a -9 first stage scaled up and with a higher engine count of the new bigger engine they are already testing 6 miles from my front porch.
Spacex's reentry experience is with simple capsules, not spaceplanes. The ITS is a sort of spaceplane hybridized with the capsule concept. It reenters more-or-less broadside, but without true wings like shuttle or X-37B (or Dreamchaser). The hybridization requires that the vehicle pitch up end-for-end to tail-first at the end of hypersonics, while in supersonic flight. This is required for propulsive landing at Mars (or here on Earth).
That supersonic attitude reversal has never before been done, and involves enormous control authority and strength against some very unusual (and very high) airloads. What they are doing with Falcon stages reversing attitude happens outside the sensible atmosphere; this inherently takes place down deep in the atmosphere. It is quite different.
THAT is where they are going to run into real troubles, and THAT is what is going to delay operational flights of this vehicle. THAT is where they need some small-scale demonstrators to solve the aero/structural issues before scaling up to the inherently-more-fragile larger size. THAT is where Murphy's Law will have impact. It's not the rocket, it will be the aircraft that vexes them.
GW
Last edited by GW Johnson (2017-10-18 09:47:40)
GW Johnson
McGregor, Texas
"There is nothing as expensive as a dead crew, especially one dead from a bad management decision"
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perhaps they will make a scale model and fly it on Falcon Heavy. It would be a lot cheaper than losing a production item.
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Hi GW - not quite following you...why does the Falcon 9 Heavy or BFR have an attitude change further down in the atmosphere? Is that because the first stage falls away earlier?
Spacex is contractually obligated to fly its Falcon-Heavy multiple times. The DOD contract it has requires that. If you look at the interval required to get -Heavy off the ground, it is about factor 2 longer than anticipated, since it was first supposed to fly in 2014, not late 2017 or early 2018. The delay is typical, because things in the launch business quite typically turn out to be be harder-than-expected. That's just Murphy's Law in action. It is to be expected, at least by those with real experience. Musk's team understands this now, even if he himself really doesn't.
That being said, I think -Heavy will give them the intermediate step they need to get from Falcon-9 to BFR. -Heavy will give them the experience they need running engine counts on the order of 25 to 30. It is about the same payload ratio to -9 as was Saturn-5 to Saturn-1: about 3 to 1.
Engine count is the main difference between BFR and -9, the others being the larger Raptor engine, and switching to liquid methane instead of kerosene as fuel. Of those, high engine count is the "biggie", that being what stopped the Russian N-1 decades ago.
Once Spacex is past the high engine count with -Heavy, then BFR does not look like such a big step from -Heavy, the payload ratio being that same factor of 3 as a step.
So it looks to me like they really are doing the essential intermediate experience steps getting to BFR, and it really is -Heavy that is the appropriate intermediate step.
The one that worries me is the ITS second stage, not the BFR first stage, which is nothing but a -9 first stage scaled up and with a higher engine count of the new bigger engine they are already testing 6 miles from my front porch.
Spacex's reentry experience is with simple capsules, not spaceplanes. The ITS is a sort of spaceplane hybridized with the capsule concept. It reenters more-or-less broadside, but without true wings like shuttle or X-37B (or Dreamchaser). The hybridization requires that the vehicle pitch up end-for-end to tail-first at the end of hypersonics, while in supersonic flight. This is required for propulsive landing at Mars (or here on Earth).
That supersonic attitude reversal has never before been done, and involves enormous control authority and strength against some very unusual (and very high) airloads. What they are doing with Falcon stages reversing attitude happens outside the sensible atmosphere; this inherently takes place down deep in the atmosphere. It is quite different.
THAT is where they are going to run into real troubles, and THAT is what is going to delay operational flights of this vehicle. THAT is where they need some small-scale demonstrators to solve the aero/structural issues before scaling up to the inherently-more-fragile larger size. THAT is where Murphy's Law will have impact. It's not the rocket, it will be the aircraft that vexes them.
GW
Last edited by louis (2017-10-18 10:56:33)
Let's Go to Mars...Google on: Fast Track to Mars blogspot.com
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Falcon-9 and Falcon-Heavy have a second stage rocket with a payload on its tip. The first stage reverses attitude outside the sensible atmosphere, and does a propulsive reentry and a propulsive landing. The second stage is not recovered on either of these. Only the payload comes back, if it is a Dragon.
The BFR first stage does exactly the same things that the Falcon-9 and Falcon-heavy first stages do. It's just bigger. There is no analog to the second stage of the smaller rockets, the second stage of the BFR is the ITS spacecraft. It burns off its propellants reaching LEO, but is refuelled there so it can go elsewhere.
It is on landing of the ITS that things are different. Whether this is Earth or Mars, the vehicle must do an aerobrake reentry at a semi-broadside attitude, but more or less nose first, based on the videos and illustrations that Spacex has put forth so far. It comes out of hypersonics at relatively low altitudes deep in the atmosphere of either planet, at about Mach 3. There it must swap ends from nose first to tail first, while in supersonic flight (!!!), in order to do a propulsive landing.
That end-swapping deep in the atmosphere is the new thing that no one has ever done. That is the part that is going to give them trouble, because no one anywhere has ever had experience doing that. Most aircraft break up when broadside to a high subsonic flow, much less a supersonic one. Both the air loads on the structure, and the required control forces, are simply enormous.
Flying subscale x-plane demonstrators with Falcon-9 or Falcon-Heavy is likely how they will have to proceed. But it ain't going to be easy. Or quick.
GW
Last edited by GW Johnson (2017-10-18 11:01:56)
GW Johnson
McGregor, Texas
"There is nothing as expensive as a dead crew, especially one dead from a bad management decision"
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Attempts to design ITS for any destination is the problem. Earth, Mars, and Moon are radically different planetary bodies. Shuttle was designed to be all things to all people; as a result it wasn't able to do anything well. This is the same mistake. We need a dedicated vehicle for Mars. If it can land on the Moon, that's bonus, but do not sabotage the design just to add Earth to is list of destinations. Design for Mars means no wings. I could argue for a modified Mars Direct architecture, with aerocapture in to Mars orbit and a Mars shuttle that is a single stage land-on-tail rocket based on Falcon-9. However, if they really want to do it this way, then design ITS to land on tail. That means no wings, no winglets, and flip outside the sensible atmosphere so it enters tail-first like Falcon-9 first stage.
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With this in mind, are there any commercial CFD packages anywhere, that can model the interaction between supersonic / hypersonic flows and structures? If they do exist, I am sure that Musk and Co will be using them. My experience of CFD is that it is generally accurate to about 30% in the subsonic region. But I have only dealt with very limited applications. Don't know at all about supersonic. Uncertainties will raise the need for larger engineered safety factors, which will of course add weight and cost.
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RobertDyck so true that designing 1 vehicle and capsule for all destination is not the correct way to to do the design at all and unless you are planning beyond orbital refueling the ability is very hampered for any of the mission durations or destinations. Adding on sub assembly of parts to make it more capable is about to only way to make it do able for all missions and durations.
This is the same problem for using any of the current launch vehicles in that none are capable enough for any missions beyond LEO at this point. With careful add on selections they do become more capable to a point and then just needs to much to be able to support the farthest away destinations. Scaling the size of the crew will make it more possible but may still need other modifications of the mission architecture to make the farthest of destinations possible.
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I see on the Spaceflight101.com website that the date for maiden flight has been pushed out to 30 December this year. It may slip into 2018. If they are having that much trouble with Falcon Heavy, just contemplate what the BFR will entail.
Last edited by Oldfart1939 (2017-10-24 10:35:13)
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Is it also true that Space x is stopping the Falcon flights as well in order to switch over to just the BFR production and design. If so then that could spell problems for Space x.....
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SpaceNut-
I think they have accumulated a backlog of previously flown Falcon 9 rockets and will continue using them until they are no longer service-worthy or are destroyed. There are probably some customers who will want new rockets, though. The Falcon 9 Block 5 should be unaffected, however. That changeover will probably be occurring in 2-3 years, based on reality. Musk is the eternal optimist, but I see further changes in my crystal ball before the latest iteration of the BFR gets built. I'm just guessing at another downsize to resemble the Falcon X. The Falcon XX is just about the same as BFR, dimensionally.
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Falcon-Heavy surprised them with the extent of the structural redesign for the added strength to fly as a cluster of 3. Look, these are rocket stages with a structural inert about 5%, which is incredibly small. And fragile.
I am exceedingly surprised these stages survive entry for landing. The only possible way to do that is end-on. The entry burn somehow pushes aside the hotter plasma for exposure to somewhat cooler rocket exhaust. That's the only possible way for aluminum to survive the heating, I guess, and I am surprised it works. But pleased.
GW
Last edited by GW Johnson (2017-10-25 11:32:49)
GW Johnson
McGregor, Texas
"There is nothing as expensive as a dead crew, especially one dead from a bad management decision"
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Interesting. Saturn V used RP1/LOX for the first stage, LH2/LOX for 2nd & 3rd stages. The reason is RP1 is less expensive. It has lower specific impulse, but for a first stage you can simply build a larger stage. For upper stages, specific impulse is very important. As an example, N1 was the Soviet equivalent to Saturn V, competing at the same time. N1 used RP1/LOX for all stages. It was roughly equivalent size, Block A actually provided more thrust. But total throw mass to trans-Lunar trajectory was less. However, RP1/LOX is cost effective for the first stage.
Delta IV used LH2/LOX, but the RS-68 engine was optimized to minimum total cost of the entire first stage. It had lower Isp than SSME, requiring large tank and more propellant. However, lower manufacturing cost of the engine more than compensated for hire tank and propellant cost. Again, don't obsess over Isp for the first stage.
So I would argue the Merlin 2 engine proposed for Falcon X, Falcon X Heavy, and Falcon XX makes more sense. Use Raptor for upper stages. However, we probably won't see it.
I have proposed an architecture for the Moon: a reusable Lunar Module, parked in Lunar orbit between missions. Dragon capsule with the trunk replaced with an actual service module with enough delta-V for TEI. Falcon Heavy upper stage used for TLI. And a new expendable stage used for LOI, refuelling the LM, and crasher stage to deorbit the LM. This would require 2 launches of Falcon Heavy for the first mission, then one launch thereafter. Should be able to recover all Falcon first stages, and the Dragon capsule. So only the Falcon upper stage, crasher stage, and Dragon SM would be expended. This requires Falcon Heavy, so I'm hoping it will fly.
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I'm backing Musk and Space X on this. I think he's got the right design...it's like a station wagon suited to all sorts of purposes: taking a calf to market, going to the barn dance, getting the kids to the hospital, taking out some hay on the farm...
I don't think you can compare it to the Space Shuttle - the fatal flaw there was non-propulsive landing which meant you ended up with (a) the problematic tiles and (b) hitching a plane to a rocket both of which fundamentally raised costs and compromised safety. Also the Space Shuttle was useless for landing on the Moon or Mars.
The BFR has all bases covered. I think this is definitely the way forward.
Attempts to design ITS for any destination is the problem. Earth, Mars, and Moon are radically different planetary bodies.
Let's Go to Mars...Google on: Fast Track to Mars blogspot.com
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I don't think you can compare it to the Space Shuttle - the fatal flaw there was non-propulsive landing which meant you ended up with (a) the problematic tiles and (b) hitching a plane to a rocket both of which fundamentally raised costs and compromised safety. Also the Space Shuttle was useless for landing on the Moon or Mars.
No, the Shuttle landing method was and is the best for an Earth orbit shuttle. The problem was attempting to design it to be everything to everyone, and slashing development cost at the expense of drastically increased operational cost. NASA requirements for Shuttle in 1968 were a lifting body to carry 7 astronauts plus 11 metric tonnes of supplies to a station in orbit 400km @ 50° inclination. It was never intended to launch satellites, or station modules, or any equipment for the exterior of the station. A "big dumb rocket" would do that job less expensively; either Saturn 1B or a new rocket that NASA had proposed but president Nixon did not authorize. Shuttle was to be Two-Stage-To-Orbit (TSTO), with a piloted fly-back booster. That booster would have a skin over the tank insulation, so there wouldn't be any ice-filled foam fall off during supersonic/hypersonic flight. Without chunks of foam coming off, the heat shield tiles were safe. Furthermore, it wasn't to have any solid rockets. Nixon said NASA and the military couldn't have separate launch vehicles, they either combine funds for one Shuttle or neither get anything. So that cancelled the Titan III launch vehicle that the military was using to launch satellites. Then a senator from Utah got himself appointed chair of the appropriations committee overseeing NASA. He said he has a company in his state that makes segmented solid rockets for the Titan III, so where are you (NASA) going to put segmented solid rockets on your new Shuttle. NASA's response was they weren't, there's no place for solid rockets on a Shuttle. That senator said no big segmented solid rocket boosters, no Shuttle. So NASA caved, added SRBs. Furthermore, Nixon's cuts meant they couldn't afford the piloted flyback booster. So they used a "drop tank" instead. That's an air force term, it means an expendable fuel tank for an aircraft to extend its range. That's what the external tank is, a giant drop tank. The military flew big spy satellites into very low orbit, so Shuttle had to carry those. That meant 27 metric tonnes to LEO, initially. It changed after a few upgrades. The size of the cargo hold was expanded to accommodate military spy satellites, and a cargo bay door was added to allow those satellites to be deployed. Remember, Shuttle was originally only going to carry supplies and equipment for the interior of a space station. And some military spy satellites use polar orbit, so Shuttle had to be able to fly that. A lifting body is far more efficient, but has limited glide range. Flying at 50° inclination (now 51.6°) a lifting body could enter Earth's atmosphere at any point, and fly to an airport somewhere. But there are no airports at the poles, so for safety they had to redesign Shuttle for greater glide range. That meant delta wing and fuselage, much heavier, the design we now know. And the military built a launch facility at Vandenberg air force base to launch Shuttle for polar orbit missions. It was called Launch Complex 6. Fully complete, but never used.
And did you know NASA was working on aerospike engines in the 1970s for Shuttle? Development cost was too high, so they chose to develop a high pressure, high efficiency, reusable rocket engine instead: SSME. That was the same engine later intended for X-33 and VentureStar.
If they stuck with a lifting body orbiter to deliver crew and supplies only, stick to Saturn 1B to deliver station modules, and Saturn 1B or smaller rockets for satellites, they would have had a much more robust and cost effective system.
Shuttle was never meant for the Moon or Mars. But in the 1960s and early 1970s, NASA had Apollo. And they designed a version of Apollo for Mars. It would have 4 seats instead of 3, PICA heat shield instead of AVCOAT, no room for food or life support supplies, the Service Module would have 3 LM descent engines instead of 1 SM main engine. And the CM would use an RTG for power, with a chunk of SM skin a radiator for the RTG, from thruster quad to thruster quad for the full length of the SM. It would have to be accompanied by some sort of deep space habitat with life support.
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The space shuttle was really an engineering form of a camel, which if you recall, is a horse designed by a committee. What did we learn from the experience? Apparently nothing, at NASA. Great synopsis, by the way, Robert.
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I would add to Robert's dissertation the diameter and length of the shuttle cargo bay, and its 20 ton payload to low-inclination LEO, derive from the shape and weight of the military KH-11 spy satellite. That one is why the MOL program was cancelled. Once the robotics worked well enough, they didn't want to incur the extra weight and size for the crew. MOL saw only 1 unmanned flight before cancellation, unlike its counterpart Almaz.
Before the shuttle turned into the cluster we know so well, like Robert says, it was a two-stage airplane design with a Mach 5 staging speed at around 150,000 feet. The big argument early on was straight vs delta wings. Straight gave much better cross-range capability, but were very much less survivable during reentry (partly from the hypersonic aero, but mostly from a structural standpoint). The double delta wing shape they ended up with is actually the best compromise for winged entry, in spite of its lousy characteristics at landing speed (steeply swept leading edges are very laterally unstable in asymmetric roll disturbances).
The AOA during entry was very severely limited during entry to 20-40 degrees, yaw and roll near zero. As a grad student slave laborer, I helped find out about that in the wind tunnel. Too low an AOA, and the quartz windscreen suffered a direct plasma hit. Too high, and there was a sort of Coanda-effect jet (really caused by the lateral nose vortices) that directly hit the windscreen. Within those AOA limits, the plasma jet jumped over the flight deck roof. The windscreen would fail within about 10 seconds if directly struck by entry plasma.
Which is exactly what happened to Columbia at about Mach 12 over the Texas - New Mexico border, when that wing came off. The air blast ripped the roof off then ripped the 4 flight deck occupants apart and out from under their seat belts. Those are the body parts found between Dallas and Tyler. The 3 mid-deck occupants survived until max-q airloads crushed the tumbling cabin section to scrap at about Mach 1 and 20,000 feet, very close to Tyler, Texas.
GW
Last edited by GW Johnson (2017-10-28 10:12:46)
GW Johnson
McGregor, Texas
"There is nothing as expensive as a dead crew, especially one dead from a bad management decision"
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Oldfart is unfair to camels. Camels can live where horses cannot.
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The bottom line is we need purpose-built landers, but the interplanetary transportation system can be a single vehicle.
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Is the BFR is just a taxi for man or will it live up to the hype of one ship capable once in orbit to transport man or cargo to mars and back will be the question.
I hope that there are lots more flights of the used falcons as with each reuse Space x is finding out just what still needs to be altered to make it a better design....
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The BFR/ITS combination plus the BFT/tankers needed to refuel it, become a practical large "container ship" transportation system to Mars, if (and only if) they can manufacture the propellant on Mars for the return trip. Otherwise, it's just another one-way stranding. And it needs pretty much the full propellant load to leave Mars and make a free return at Earth, with some left over for its propulsive landing. There's no magic here, that conclusion results directly from the tyranny of the rocket equation.
They learn how to make high engine count reliable flying Falcon-Heavy (27 versus 33 in the new downsized BFR). The Falcon stage recoveries will contribute directly to BFR recovery, and indirectly to propulsive landings of the ITS at Mars and at Earth. They're testing the bigger engine the bigger vehicle will use, and they've built the first (of what must inevitably be several) fuel tank assemblies to prove out tank structures on such a scale.
The missing piece here is the nose-for-tail pull-up reversal for landing the ITS or tanker second stages. Unlike the Falcon and BFR recoveries, which change attitude outside the sensible atmosphere prior to entry, the ITS (and tankers) will have to do this deep in the atmosphere (45,000 feet-ish here, maybe 5 km on Mars). I dunno whether they will (or even can) wait for subsonic speed to do this maneuver. Seems possible here, probably not possible to wait at Mars. Which means a supersonic nose-for-tail flip at Mars.
Challenging development. Subscale test vehicles flown on Falcon-9 or Falcon-Heavy? No one is saying yet. No one has ever done this before.
GW
GW Johnson
McGregor, Texas
"There is nothing as expensive as a dead crew, especially one dead from a bad management decision"
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Hinted elswhere the SpaceX aims for late-December launch of Falcon Heavy
Whats not being talked about is just how many missions will the heavy really fly or just how soon after the trial run.....
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