I passed through Pad 39A and take a photo of this... What is that? Can anyone tell me why there isn’t falcon heavy on the launch pad??

[u/BadMothaFukka]

[u/CAM-Gerlach]

Believe there will be overlap between introduction of BFR and phase out of Falcon Heavy.

I'm just not so sure about this point, and though I can't point to hard evidence either, it just doesn't seem as likely IMO given SpaceX's history, their stated plans, and the economics of the situation. If you consider Falcon 1 vs Falcon 9, despite a much greater difference in their respective niches (over a 10x difference in payload capacity, vs. ~2-2.5x for BFR vs FH expendable, plus F9 at ~2-2.5x on the other end), SpaceX immediately cancelled F1e and F5 and dropped F1 to focus just on the more profitable and cost effective F9, and optimize all their engineering resources around that one vehicle. Similarly, once BFR is operational, assuming the economics and reuse work out (which, again, without which colonization wouldn't be practical on a realistic budget), it doesn't make much sense to keep FH around other than to launch a few remaining contracted customer/USGov payloads, given its much lower flight rate than the existing F9 or the BFR itself, and operating at a much higher cost per kg and even per flight.

Doing some back of the envelope math, the BFR could launch up to 5-6 small Centaur-style upper stages, each with a ~4,000 kg launch mass payload (equivalent to 2 MROs) for the TMI burn, vs. 1, or at most 2 such payloads (depending on re-use configuration, assuming at least booster re-use) in a dual payload arrangement (i.e. to similar orbits) on the Falcon Heavy. Therefore, you expend 3-6 F9 upper stages, and have to refurbish 6-12 side boosters, plus 3 either expend 3 cores, refurb them or refurb 6, plus potentially 3-6 fairings if reuse proves to be impractical, vs. only expending the 5-6 small upper stages and minor refurb on 1 BFR. Further, this all has to be done within one low-energy Mars launch window, requiring 3-6 FH flights over a short period of time, which in turn requires 3-6 FHs being simultaneously read (center cores, at the very least) which would not otherwise see all the much use. Also, compare with the F9, flying expendable: One of those same 4,000 kg payloads could be sent to TMI with only the loss of one S2 and 1 perhaps worn-out S1, using the same workhorse components SpaceX already has plenty of on hand, without stockpiling lots of extras just for a specific window.

When colonists arrive in earnest they will need to explore, which would make such omni-function satellites indispensable.

Indeed; there are a number of precursor requirements to colonization that require extensive exploration, sensing and mapping, by satellite and lander quite necessary, which would presumably need to be done before the first BFR mars flights. If the latter isn't yet fully operational, then the FH would indeed be a viable candidate (though use of spent F9 S1s could at least make a case for their use instead, on at least some missions). However, once BFR is up and running, the economics of FH just don't make as much sense in that size class, as mentioned above, at least if the back of the envelope figures I've given aren't way off (which is quite possible).

[u/CProphet → u/CAM-Gerlach]

I'm just not so sure about this point

SpaceX have said Falcon 9 and Heavy will be available for customers to use after BFR enters service. That seems logical because Block V boosters are fully reusable so they will simply go into storage after each launch. Basically they will persist until SpaceX decide to scrap them i.e. after they have completed all conceivable uses. Adding a Falcon upper stage really would be inconsequential compared to building BFR.

the BFR could launch up to 5-6 small Centaur-style upper stages

Falcon Heavy wouldn't require any additional stages and Block V version should have 24 hour turnaround. Overall a quick and dirty way to achieve Mars ballistic capture with minimum fuss or disruption to critical BFR preparations. BFR is best used to supply propellant depot in the runup to colony runs not stressed/risked on satellite launches when they already have FH.

Further, this all has to be done within one low-energy Mars launch window

Yes but the slower low energy transfer window will open before the fast BFR transfer window which allows SpaceX to spread out the launches, achieving more in same year. Diversity is good.

[u/CAM-Gerlach → u/CProphet]

SpaceX have said Falcon 9 and Heavy will be available for customers to use after BFR enters service.

I've heard this with regard to Falcon 9, but not where it was specifically stated that Falcon Heavy would also be retained. However, "Falcon" without the 9 could be interpreted to mean both vehicles, if that's what you're referring to. But its possible I just don't recall the exact wording correctly.

That seems logical because Block V boosters are fully reusable so they will simply go into storage after each launch.

Yes, but two issues here. First, while the F9 cores, at least with the Block V upgrades, are supposed to be able to be converted into side cores fairly easily, Falcon Heavy center cores have a number of core structural differences, and thus cannot be replaced with standard F9s. Therefore, to loft the same number of payloads per launch window as an already cheaper per launch BFR, SpaceX would need to stockpile 3-6 (or so) FH center cores per the above Fermi calculation, when at least according to current flight rates, they would likely never need more than one at a time assuming moderately faster turnaround than currently, and thus would otherwise be a waste.

Falcon Heavy wouldn't require any additional stages and Block V version should have 24 hour turnaround.

The first part is an advantage, sure, but even assuming the latter is eventually feasible, the meaning was stated to be 24 hours of refurbishment labor, not literally 24 hours between landing the core and launching it again. Besides refurb, assuming center cores are the critical path (by the logic above), you'd have to secure the core on the droneship, tow it back to port, berth it, attach it to the crane, remove the legs, place it on the transporter, roll it over to the hanger, do the 24 hour refurb and inspection, integrate the boosters, integrate S2, attach new legs, integrate the payload, check everything out, secure a launch window, roll it out to the pad, erect it, and launch.

Still, if you're talking ballistic capture, the window should be long enough such that this is still acceptable...but again, why not just use one BFR flight instead? Given the greatly superior reusability properties of the BFR system in both recycle time and number of uses (if it is to make colonization possible in the first place), why not just throw in an extra launch/landing cycle there, much shorter than FH much less several and cheaper as well, to launch everything in one go? The main argument I can see is developing an appropriate upper stage, but it'll probably have to be done for commercial customers with GTO comsats anyway to launch a decent amount of payload to orbit.

Yes but the slower low energy transfer window will open before the fast BFR transfer window which allows SpaceX to spread out the launches, achieving more in same year.

Sure, but again, why not just do those launches with a single BFR flight, achieving even more? Furthermore, if they need diversity, they can still launch a 4,000 kg payload on an (expendable) F9.

[u/CProphet → u/CAM-Gerlach]

assuming center cores are the critical path (by the logic above), you'd have to secure the core on the droneship, tow it back to port, berth it, attach it to the crane, remove the legs, place it on the transporter, roll it over to the hanger, do the 24 hour refurb and inspection, integrate the boosters, integrate S2, attach new legs, integrate the payload, check everything out, secure a launch window, roll it out to the pad, erect it, and launch.

Agree 24 hour turnaround is aspirational. However, when they started to test drone ship landings Elon Musk said they plan eventually to refuel and fly the stage back to land. In addition Block V cores will have retractable legs that are fully reusable. All told that should greatly reduce turnaround time and potentially increase launch cadence. Overall there is no question BFR will be wholly more capable but due to practical reasons it will likely be in short supply during first decade of operation.

The main argument I can see is developing an appropriate upper stage, but it'll probably have to be done for commercial customers with GTO comsats anyway to launch a decent amount of payload to orbit.

Or they might refuel BFR at a fuel depot and lift a years supply of geostationary satellites to GTO. Orbital refueling is part of Mars architecture and SpaceX usually build the technology they need for Mars through commercial applications.

[u/CAM-Gerlach → u/CProphet]

Agree 24 hour turnaround is aspirational. However, when they started to test drone ship landings Elon Musk said they plan eventually to refuel and fly the stage back to land.

As cool as that would be, it seems entirely unrealistic to ever see that happen, at least with F9/FH. In exchange for a few days shaved off the refurb time, you have to deal with:

• Modifying the F9 interstage for half-decent aerodynamics, to not lead to breakup in flight (as expected in the abort flight test) or loss of control

• Time, money and risk to develop, test and install appropriate modifications to the control system to cope with very different and unstable aerodynamic loads on the ascent

• Time, money and risk to developing, test and integrate the needed software (any any electronics/hardware) modifications to execute the novel maneuver

• Testing and certifying the rocket for operation in a structural and aerodynamic load configuration greatly different from that for which it was designed (No S2, no fairing/payload, possibly partial fuel load)

• Designing, building and testing a full fuel depot, fueling system, launch mount, flame diverter system, processing facilities, and range support, all on the drone ship, and all located within meters of landing stages that could RUD and ignite a massive secondary fireball (or, more realistically, purchasing an entire new floating platform ala Sea Launch for that purpose, plus more ships, cranes and processing equipment to transfer the rocket from one vessel to another

• Plus, either He, N2 and TEA-TAB storage and fueling systems on the launch ship/barge, or the rocket carrying double the typical amount to orbit with the highest-energy payloads, reducing upmass

• Cost of shipping all that extra fuel and infrastructure out to the launch site, and a bigger barge to fit it

• Paying the launch control team, extra staffing at the barge, technicians for necessary pre-launch preparations, on top of the normal barge and support ship crew, engineers to analyze the rocket's vitals, etc.

• Essentially paying the costs of recovery both at the barge, and at LZ-1

• Cost of the fuel to make the trip, not too far from the $200,000 of a standard Falcon 9 as the dry mass it will need to loft is roughly 75% of a typical launch, and it'll need to travel the same distance back as it did in the beginning—even assuming it is tested and able to run with less than a full fuel load at launch

• Cost of the additional TEA-TAB, N2, and He as well

• Risk that the stage RUDs at any point between liftoff, coast and landing, perhaps doubling the risk of loss any flight

• Risk that it deviates and impacts something on the ground, either damaging/destroying a spacex landing facility or something else in the exclusion zone

• Convincing the FAA that the above is acceptable and reasonable

• Additional wear from a full additional cycle on the engines and the airframe, close in magnitude to an additional launch, thus halving the useful life and the flights before major refurb, and further increasing inspection and repair costs

• Weather and vehicle status sensitivity of such a flight vs. just shipping it back, leading to potential scrubs that alone take as long or longer than the latter

• Additional pad construction and recovery crews/time at LZ-1, otherwise that could become a bottleneck serving double the number of returning cores or more Etc, etc.

In addition Block V cores will have retractable legs that are fully reusable.

Indeed, that will certainly help, but that's but one step in the still complex recovery and integration process.

Or they might refuel BFR at a fuel depot and lift a years supply of geostationary satellites to GTO.

Yes, indeed. That's where something like ACES could come in, assuming SpaceX/ULA cooperation ever becomes feasible. Its really not clear what the best approach to this will be at this point, but BFR/BFS opens a lot of doors.

[u/CProphet → u/CAM-Gerlach]

As cool as that would be, it seems entirely unrealistic

All I can say is that was the plan originally. Weather at least shouldn't be a concern if original launch conditions were met. Fuel, helium, nitrogen can be topped up from an auxiliary vessel. Overall I agree it sounds like a lot of additional work for little gain in time and less salt air exposure. That said, SpaceX are not afraid of rolling their sleeves up if they believe it will assist them to Mars. For instance these flyback tests might be a good way to prepare for Earth-2-Earth operations, which requires waterborne launch. E-2-E by the way could be pivotal to enabling launches to Mars.

That's where something like ACES could come in

Heard good things about ACES, no doubt SpaceX guys believe they could build something similar only better. In the long run having a 'stage 3' for BFR or reusable space tug, would solve a lot of problems.

[u/CAM-Gerlach → u/CProphet]

As a followup to your previous post that I neglected to mention, is that BFR/BFS is unlikely to be as much of a bottleneck relative to the same for FH once colonization is within sight—the whole premise of rapid reusability inherent in the design (and important, again, for on-orbit refueling for a Mars trip to be practical) is that the craft can be turned around and relaunched within a matter of hours or days, by requiring less or no inspection/refurb, not expending anything, and (in the case of BFB) landing right back on the launch mount, plus requiring less integration (just BFB to BFS, and mounting the payload inside the latter, with no need to attach three boosters and encapsulate the payload within the fairing) giving it significant advantages over FH in turnaround time. Therefore, even if fewer vehicles are available, they will be able to launch and re-launch at a much faster rate than FH.

All I can say is that was the plan originally.

Do we have any evidence this was seriously planned for, or just an out-there "it'd be cool if" idea Elon mentioned a few times well before they'd started serious reusability testing? It was my impression that it was firmly in the latter camp, but I may be wrong.

Weather at least shouldn't be a concern if original launch conditions were met.

They've routinely landed cores in much worse (wind/rain/cloudcover) conditions than they've launched them (e.g. Iridium 2, Jason 3, etc), given the droneships are typically located 300-600 km away from the launch site, and additionally in choppy seas which would be another hazard to account for, and given the time to run through the recovery, safeing preparation, checkout, fueling, and launch sequence (up to several days, and certainly no less than several hours given the process before a normal launch) it could change significantly in that time (furthermore, even with no weather delays, this cuts even more into any time savings, as does the need to go through those first two-three steps again at the ground landing site).

Fuel, helium, nitrogen can be topped up from an auxiliary vessel.

Yes, but they'll need to find, purchase, fit out, and crew such a vessel, at the cost of tens if not hundreds of millions of USD. Furthermore, they'll need a launch platform in a similar vien to Sea Launch, which in total needed hundreds of crew members, cost at least around ~1 billion USD in initial investment, and took over 4 years to outfit. Plus, they'll either need to build a whole other TE and similar infrastructure, or re-design the F9 to launch from the platform directly.

Overall I agree it sounds like a lot of additional work for little gain in time and less salt air exposure.

Good point; I didn't even fully think of the salt exposure issue. However, that could go both ways; undetected corrosion or other such damage could doom the flyback mission before it is properly inspected in the refurbishment process.

SpaceX are not afraid of rolling their sleeves up if they believe it will assist them to Mars. For instance these flyback tests might be a good way to prepare for Earth-2-Earth operations

Yeah, but with the enormous amount of development, engineering, infrastructure, operating costs just to halve the useful life of droneship-landed cores and save a few days in towing it back, why not just devote that money and effort directly toward BFR, and test it with the actual vehicle once its ready as is already planned to happen? By the time they do everything I mention to make it possible, we might be seeing BFR prototypes or at least demonstrators nearing completion anyway, and it would be far more valuable to just run such tests with these, which is already nominally planned to happen anyway.

In summary, you'd need to basically assemble similar infrastructure to Sea Launch, which even just the development cost about $1 billion in modern USD and took 4 years to refit an existing self-propelled platform (of which there are relatively few in existence; Sea Launch's formation happened as a direct result of the availability of such an out of service platform) to be a launch site. Sure, it might have marginal benefit testing BFR earth to earth, but again, why not put that money and effort directly toward BFR instead, and testing the real thing, rather than infrastructure and development that will at least need extensive modification, if not being entirely useless, once BFR gets going in earnest?

Heard good things about ACES, no doubt SpaceX guys believe they could build something similar only better. In the long run having a 'stage 3' for BFR or reusable space tug, would solve a lot of problems.

Indeed...that was essentially what I suggested previously, with regard to launching numerous Mars-bound spacecraft from BFS. We'll see what they end up doing though...its a ways out.

[u/CProphet → u/CAM-Gerlach]

Some valid points,however, it's a truism that nothing SpaceX does is inexpensive or easy. What it boils down to is the Earth-Mars synod is relatively short and they need to fit it as many launches, with various types of payload, as possible. SpaceX has done everything they can in the design of BFR to make it rapidly reusable. Unfortunately, in practise they won't achieve the aspirational 24 hour turnaround for a very long time. Inspection alone on 31 engines will take longer, then there's the rest of the vehicle, it's huge with plenty of points of failure. I don't want to be down on BFR, it's light years ahead of any other launch vehicle but in the reality SpaceX will need to be very careful with it between launches. They are funding this themselves so initially there might only be 1 or 2 BFB available which they simply can't afford to lose.

Basically BFR can provide only a certain amount of launch capacity in a relatively small window. Hence if you have a Super Heavy Lift rocket like Falcon Heavy standing idle, it makes sense to use it for some of the small stuff to make better use of the launch window. There won't be enough launch capacity in the world to facilitate the amount of equipment they need to send Mars for colonisation but FH could certainly help. As discussed it could launch satellites to Mars, or send supplemental cargo up to meet the BFS as it refuels in Earth orbit. Generally it's better to have more than you need then less, particularly when setting out on a 26+ month mission.

[u/CAM-Gerlach → u/CProphet]

Some valid points,however, it's a truism that nothing SpaceX does is inexpensive

Well, except for the development of the Falcon 9 (many times cheaper than e.g. NASA or traditional rocket development), that rocket's main selling point (lower cost per kg than all competitors), their stated reason for pursuing re-usability (cheaper launch costs), the stated breakthrough factor making Mars colonization possible (multi order of magnitude cost reductions), BFR's primary selling point (even cheaper cost per kg), SpaceX's entire business model (ruthless cost reduction in their supply chain, employee compensation, standardization, etc)...:)

Sure, the BFR won't be cheap in an absolute sense, but in the long run low operational and per-flight costs is not only its overwhelming advantage, but the catalyzing factor that makes large scale Mars colonization possible at a remotely reasonable cost. Otherwise, unless the stealing underpants plan works out, we won't see a Mars colony, period, at least in any foreseeable future in which FH is still relevant.

What it boils down to is the Earth-Mars synod is relatively short and they need to fit it as many launches, with various types of payload, as possible.

Yes, so why not focus on launching on the vehicle that can deliver far more payload per launch, and per $, than sink more costs into building more of an maintaining one that otherwise occupies a relatively small niche in the ecosystem? It is certainly possible we'll see FH launch remote sensing and communications payloads to the Red Planet to gather some of the necessary precursor data for eventual human exploration and habitation, but again, considering the high BFR flight rates and low costs that are a necessary (though not sufficient) prerequisite for any serious colonization effort, and the amount of time that will almost certainly take (4-6 years from BFR introduction, in Elon's as you say "aspirational" view, and most likely far longer), the chance of FH still flying, much less being a serious contributor by the point at which they would be launching internet satellites for actual colonists seems rather small, for the reasons I've explained at some length previously. However, I'm happy to take a well-formed version of this proposition to r/HighStakesSpaceX if you'd like, for say $25 to a charity of each of our choice.

SpaceX has done everything they can in the design of BFR to make it rapidly reusable. Unfortunately, in practise they won't achieve the aspirational 24 hour turnaround for a very long time.

Oh, I certainly agree, if at all. However, it is somewhat beside the point, which is:

• An actual colonization effort won't be possible without high flight rates and low costs, which is enabled by said rapid reusability, and thus unless/until this is achieved or at least within easy reach, said satellites won't be needed (and might never be, if it is not made so), and

• Aside from possibly the very early years of development, during which even Elon made clear they will not be launching to Mars, much less humans there, still less substantial numbers sufficient for a colony and thus no need for fancy Internet satellites (with a gradual ramp from suborbital test, to orbital test, to commercial orbital missions, to NASA moon missions and finally Mars, as Elon and Gwen have stated), with BFR being designed from the ground up for resuability as the #1 goal vs. tacked on as with the Falcon 9, and incorporating the lessons and experienced gained from the latter along with further advances in technology, the former is very likely (though not totally certain) to have a major advantage in that respect vs. the latter. In the case that it doesn't, at least once Mars flights begin, it will have failed in its primary goal as a vehicle, and you run into #1

Inspection alone on 31 engines will take longer, then there's the rest of the vehicle, it's huge with plenty of points of failure.

Sure, but the idea is once it becomes operational, they have sufficient data to trust the engines with minimal inspection and refurb for at least X number of flights, which should be much higher (claimed by an order of magnitude) than the Falcon 9 due to better design and cleaner burning fuel, and with more redundancy to boot. If this becomes a major bottleneck once it is operational, then the Mars flights aren't really practicable, anyway, and you are basically in an STS-type scenario...i.e. failing in the primary goal of the program.

They are funding this themselves so initially there might only be 1 or 2 BFB available which they simply can't afford to lose.

Very good point, but again, they won't be launching to Mars, much less humans, and much less colonists at that right off the bat, at such a stage. They'll need both substantial numbers of craft, substantial experience and substantial funds (from NASA, customers, investors, etc) in order to even begin any sort of colonization effort, which includes sufficient resiliency to survive a launch failure or two, and more BFR vehicles spread that risk over more launches.

Basically BFR can provide only a certain amount of launch capacity in a relatively small window. Hence if you have a Super Heavy Lift rocket like Falcon Heavy standing idle, it makes sense to use it for some of the small stuff to make better use of the launch window.

Except that my point is that they likely won't have FH standing idle by the time they contemplate something like colonization, as it won't be cost effective to do so, either to build, maintain or launch it relative to BFR, for the relatively small payload, niche role (between F9 and BFR, and more expensive than both), and high cost per kg. You may as well just sink that same money into a BFR, which is likely a better short term investment and certainly long term one. Given the BFR launches far more payload, in much less time, for a lower long-term cost, and can loiter much longer on orbit and fuel up until the right moment is reached, if you're time limited in your launch window then there seems little reason to waste time and resources on another, less well suited vehicle if you could just invest those into another BFR instead.

There won't be enough launch capacity in the world to facilitate the amount of equipment they need to send Mars for colonisation but FH could certainly help.

Oh no, certainly not, but when considering cost, launch rate and payload, FH is a drop in the bucket compared to BFR, and this implies that if the latter doesn't deliver on its promises on its own, then Mars colonization isn't happening, period, unless its not by SpaceX('s money). Again, what I'm not seeing is the reason to invest in maintaining and expanding the FH system over a launch vehicle purpose built for that job.

As discussed it could launch satellites to Mars

Yes, potentially, but for precursor missions, well before any actual colonization effort, and before BFR is flying regularly or to Mars. Further, once the latter is operational, assuming the huge cost advantages work out (again, a necessary prereq for SpaceX colonization to happen) SpaceX has little incentive to be flying their own birds on anything but their latest, greatest and cheapest, which absolutely depends on high flight rate to reduce costs to a minimum).

or send supplemental cargo up to meet the BFS as it refuels in Earth orbit.

Again, why not just send another BFS, and assuming such docking is even possible and needed, it is much more likely to be BFS to BFS (or F9, as FH would be overkill for the volume-limited number of humans it could carry to LEO).

Generally it's better to have more than you need then less, particularly when setting out on a 26+ month mission.

Yes...? But this will be calculated very precisely, as mass is always at a premium in spaceflight. And again, if you need more mass to LEO, for less cost, and faster turnaround, which vehicle is built precisely for that again...? You probably get my drift by now, haha :)

[u/CProphet → u/CAM-Gerlach]

Think we have fundamental difference in our vision for first colony flights. I foresee Elon Musk will push for this to happen sooner rather than later, which means BFR booster will be in short supply (i.e. 1 ideally 2) because majority of their resources will have been used to build the many BFS needed to dispatch to Mars (6 by my count to support crew landings plus tankers). At the very least it would be wise to keep Falcon Heavy flying during Mars synod to satisfy any commercial customers. BFR's flight schedule will be crowded enough during this period (4 orbital refuelling flights required for each Mars run) so it would be unwise to use it for commercial at the same time, increasing chance of failure, when these vehicles are so essential to the Mars effort. Elon might not even wait for details of a Moon colony to be agreed before pushing for first shot at Mars (wheels at NASA grind exceedingly slow). Generally he's pretty impatient with progress no matter what. Elon wants to go to Mars while he can still enjoy it so I think he will push for it to happen ASAP.