I don't know if we're talking past each other here or if you're just missing the message I'm sending, but if you build a satellite that can only go on FH, there are no other options.
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I don't know if we're talking past each other here or if you're just missing the message I'm sending, but if you build a satellite that can only go on FH, there are no other options.
Indeed. FH fairings are, if I remember right, 4,6m ID. Pretty much a standard size for modern launchers. You run into problems if you design for something like, say, SLS with its larger fairings, and then that gets cancelled.
As this conversation started months ago, allow me to re-align: context is maximizing FH capacity, which explicitly means both volume and mass.
If you build a GEOcomm that can physically fit into a typical heavy lifter fairing (and thus also the current FH fairing) but with higher mass than those normal heavies can lift to a typical-ish GTO, you’re properly screwed out of riding on any of those normal heavy launchers.
Yes, you could most likely ultimately raise that heavy satellite to GSO after riding on one of the regular heavy lifters, but the useful life would be so short that the mission wouldn’t make financial sense in the first place.
That is a great shot.That article shows an FH photo I hadn’t seen before. I appears to show the vehicle just before sliding the TEL underneath it. Awesome!
The caption from the article says:
The article also states that the DH has 3 x 700Klbs thrust rockets, so that's a total of 2.1mil lbs thrust. The FH is something like 5.1mil I believe. So that agrees with the "performance dramatically outclassed" comment...
So what is the "highest-energy" mission profile that a DH is capable of that a FH is not? Is this related to second stage somehow?
Well, one would presume that because of the higher ISP, DH would win on very light payloads launched to very high dVs. Something like New Horizons. Of course, if one were designing for FH, instead of keeping it light they'd give it a boost stage, and thus could get even higher dVs.
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I heard that even that's not true anymore. Any F9 core can be configured to perform the job of either center or side cores of FH.
That gives SpaceX massive flexibility.
At the same time the biggest competitor of FH is F9 itself. It's lofting some significant payloads into sub GTO already.
Lots of customer might choose to build a satellite with more fuel, launch it on F9 and do more of the boosting to GEO on itself. With a fully electric bird the extra mass requirement would be fairly modest, trading off for transit time, or use a few extra tons of Hydrazine it conventional (or hybrid) propulsion is used. SES-12 is one such example. It's taking months to get to GEO with 5.4mT of launched mass.
Elon confirmed that is not the case on twitter not long ago. The FH center core is special and can only be used as a center core.
Any F9 can be a FH side core though.
The military's launch, STP-2, has been pushed out into 2019. So Arabsat will be the next FH launch sometime toward the end of this year.
e-FTW
New electron smell
I spotted something else in that article (I had the same question about performance in high-energy launches) that warrants further detail that I do not have:
What is the story here? What does “dirtier” mean exactly?
It's a bit of a red herring, since pollution from rockets is a vanishingly small fraction of global emissions, and LOX/RP1 is much cleaner than a lot of other propellant mixes - but it is sootier than LOX/LH.
Mike1080i
Member
I think you are talking past yourself. No one else that I'm aware of is talking about building satellites that only can fly on FH.
My understanding is that one significant issue with kerosene/LOX is that the kerosene creates a lot of soot. You can see it on the sides of the recovered launchers. Soot isn't just unsightly, it gets into lots of places that are better cleaner, so for reuse creates a risk.
Yeah, that's one of the selling points for LOX/CH4: it's not nearly as sooty. Higher ISP, too (but lower density). Easier to ignite as well, and of course easier to manufacture offworld (and as for Earth, a lower CO2 footprint). All while being much higher density and much easier to handle than LH (LH is a PITA, and crazy low density). It's cheap, too - while historically fuel process haven't been a major portion of the cost of rocket launches, SpaceX of course is trying to make the rockets cheap enough to operate that fuel costs become the primary driver.
I'm also a fan of LOX/Propane, but it's only rarely been pursued (even less often than LOX/CH4). It can share a common bulkhead with LOX, and at those temperatures it's nearly as dense as RP1, but with a higher ISP.
The author seems to be a pretty solid spacex fan, so perhaps the intent was to not show any bias toward the "more polluting" falcon in the DH article. Perhaps a bit of 'credit where credit is due' type of intent? In reality there's still a bit of the long tailpipe aspect, as there's still plenty of energy (not to mention resources) required to produce and store the hydrogen used on Delta 4.
Indeed.
If I may provide some internet advice: I'd encourage you and @KarenRei to not quote and respond to posts on a specific subject if you do not wish to discuss those subjects.
ccutrer
Active Member
Now now, I’ve thoroughly enjoyed reading many discussions that started out as someone less knowledgeable about a matter proposing/commenting, and then someone more knowledgeable jumps in providing information to all. It only becomes a problem when back and forth happens for many pages, with the same things being repeated over and over. As can often happen in these forums!
Totally agree! For me its not even about who has more or less knowledge; I enjoy the simple exchange of information and ideas regardless what someone knows or has experienced. I like sharing what I know as I happen to have more insider knowledge than most, plenty of other people have more specialized technical knowledge than me (satellite design and production is my wheelhouse) and its really fun to see all the people here that are super in to the technical details of F9/FH.
It only got weird when two of the three people explicitly involved in a particular topic suggested they were not part of that discussion.
e-FTW
New electron smell
Well, with all of that said, I gotta say that “self-immolation” the Delta IV Heavy does on ignition is pretty bad ass.
Wonder what the BFR with its Methalox will be like.
Ok, back on topic!
Wonder what the BFR with its Methalox will be like.
Ok, back on topic!
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