Comment by Robotbeat | Hacker News Reader

Comment by Robotbeat | Hacker News Reader

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Falcon Heavy is just a toe in the door of super heavy launch. BFR will have 31 engines at liftoff compared to Falcon Heavy's 27. BFR will be about twice the thrust of Falcon Heavy, and most importantly BFR is not just a launch vehicle (which gives SpaceX a big edge in deploying megaconstellations of low-latency internet satellites), but the upper stage part will be a spacecraft capable of reentering the Earth's atmosphere with a payload and crew like Shuttle but also capable of being refueled and landing on (and taking off from) distant worlds. Falcon Heavy really helps provide this necessary interim step, and will help build a manifest of large payloads that BFR will be able to take over.

SpaceX is increasingly serious about BFR, their next-gen rocket which is like an enormous, fully reusable hybrid of Shuttle and Falcon 9 using soot-free and higher performing methane (which can also be made on Mars in a fairly straightforward process) instead of kerosene.

Musk mentioned BFR multiple times in the pre-launch press conference yesterday: https://soundcloud.com/geekwire/elon-musk-discusses-the-laun...

They're cancelling lunar Dragon+FH to focus on BFR which is making more progress than they expected. They plan to start flight testing the upper stage/spaceship portion of it by next year according to Elon in the prelaunch press conference.

Falcon Heavy was originally supposed to fly about as often as Falcon 9, but they upgraded Falcon 9 so much that now they barely need Falcon Heavy, as amazing as Falcon Heavy is.

Super excited about all this.

yeah i think BFR and the upgraded Falcon 9 pretty much obsoletes Falcon Heavy almost immediately. The Heavy just took so long to put together, it was suppose to fly 4 or 5 years ago right? I've heard it reported that the Falcon Heavy engineering was much harder than anticipated. Does anyone know what some of the major obstacles were? The concept seems straightforward but where did they start getting into trouble?

I remember reading a quote from Elon where he says that at some point, they realised it's less "strapping three cores together" than "flying three cores in very close formation"

The stresses involved are truly enormous, and the whole thing must be very well balanced to avoid putting even more stresses on the frame.

Something as stupid as fueling the rocket needs to be done with care, as they're dealing with super-chilled liquid oxygen: The cold temperatures make the rocket contract a little bit, you have to make sure all three boosters contract exactly the same otherwise you can break the attachment points.

After countless hours of experimenting with additional struts in KSP to keep my rockets from going through RUD I have a weird feeling as if I understand this on some level. Rationally, I don't think that I have any real understanding of rocket science from KSP - but that weird feeling just won't go away.

My understanding is that the center core was nearly a complete redesign because of the greatly increased load from the side boosters.

The structure in the core is beefed up a lot, but I wouldn't call it nearly a complete redesign as the other functions remain basically the same. Nearly complete structural redesign, I agree.

One of the things that slowed it down a lot was the continual development of the Falcon 9.

With the Block 3/4/5 series of the Falcon 9 (5 is the final design and mostly focused on reusability upgrades, 4 is interim) they have a relatively stable base rocket to develop the Heavy variant against.

Yeah, the regular Falcon 9 is so much stronger nowadays, it can basically do what was planned for Heavy back in ~2015. Just at the thrust difference between Merlin engine iterations (https://en.wikipedia.org/wiki/Merlin_(rocket_engine_family) ), and add the fact that the stage is longer than before, and you have a pretty capable base rocket.

You can read about the dramatic improvements here too: https://en.wikipedia.org/wiki/Falcon_9

BFR could easily run into similar delays giving Falcon Heavy a longer useful life.

It might be a "build it and they will come" thing, but what is the current market for super-heavy payloads?

By making the booster bigger, you have much more margin for making everything reusable. And once everything is reusable, marginal costs approach the cost of fuel rather than the cost of the rocket.

And of course, you can put more than one payload on a booster.

After all, we don't have a single 747 for each passenger, or for each package we fly.

At the moment? Large satellites, ISS modules, one-off scientific missions (e.g. Mars rovers, JWST, a mooted Europa mission).

Musk has said BFR is very much about Mars colonisation.

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