totm nov 2023 SpaceX Discussion Thread

[RedKraken]

Some ITS predictions from reddit :

https://www.reddit.com/r/spacex/comments/6zxmzf/official_rspacex_iac_2017_updated_bfr/

and from NSF :

http://forum.nasaspaceflight.com/index.php?topic=43035.0

http://forum.nasaspaceflight.com/index.php?topic=43757.0

 

For me : 20% ITS with 1MN engines. LiAl tanks. 6.4m, 2000t.

[sevenperforce]

When is Elon giving his speech on mini-ITS, again?

[cubinator]

9 minutes ago, sevenperforce said:

When is Elon giving his speech on mini-ITS, again?

Not never.

[RedKraken]

https://www.reddit.com/r/spacex/comments/70fv7g/elons_iac_talk_is_2pm3pm_acst_on_friday_29_sept/

7 days to wait.

[Northstar1989]

10 hours ago, tater said:

I see less and less need for FH, honestly. F9 improvements have been so fast and furious that it eventually becomes an issue of having yet more mass capability than is really needed given possible fairing sizes (even with an increase).

The real tell will be Musk's talk in a few days about ITSy. ITSy obviates any need for FH, IMHO. When FH was thought to be easy, then sure, why not. If it turns out to be a problem, then it might not be worth future trouble.

SLS has the benefit of diameter, which for manned spaceflight applications is non-trivial (people live in volumes). NG will be a serious threat to SLS for exactly that reason, even with lower masses to LEO. ITSy kills SLS dead, IMO.

Regardless, I think FH is a dead end, though it might fly for a few years.

Tater, you *DRASTICALLY* underestimate how much payload-fraction you have to lose for reusability.  Particularly upper-stage reusability, which Musk badly wants to pursue, but isn't even remotely possible for many of the Falcon 9 payloads.

With the Falcon Heavy they can achieve FULL reusability for a much wider variety of payloads.  The Falcon Heavy can lift 50 tons to LEO, but 30 tons of that might have to be sacraficed for full reusability of ALL stages...

 

CORRECTION: Wikipedia says the Falcon Heart's expected mass to LEO was recently updated to 63.8 tons in expendable mode.  Still, I exoectbthey could lose more than half of thst with reusability of all stsges, maybe as much as 75% of payload-capacity...

 

But, if that can enable upper stage reusability, it might be worthwhile.  After all, fuel is dirt cheap compared to the cost of building a rocket, and they could bring down some of the refurbishment costs by increasing the design's safety-margins on future updated versions...

"Most Boosters!" is always one way to overcome a loss of payload-fraction, like is necessarily required for full rocket reusability...

Edited September 22, 2017 by Northstar1989

[Northstar1989]

6 hours ago, sevenperforce said:

When is Elon giving his speech on mini-ITS, again?

By the way, you heard he decided to downsize the rocket to "just" 9 meters in diameter?  I'm really excited about that, actually, because it helps ensure a higher launch-volume (split the same payload among more launches) and the ability to still use existing manufacturing facilities- which are both excellent ways to save money... (and it's money, more than anything else, that will ultimately determine if humans ever colonize Mars...)

Now if only somebody could convince Elon to make use of Cycler Ships, or electric thrusters, or dedicated Mars landers... (all potentially HUGE cost-savers)

Edited September 22, 2017 by Northstar1989

[tater]

With ITSy I don't see them pursuing a fully reusable upper stage.  Why work concurrently on 2 different modalities for orbital stage reuse?

[Northstar1989]

57 minutes ago, tater said:

With ITSy I don't see them pursuing a fully reusable upper stage.  Why work concurrently on 2 different modalities for orbital stage reuse?

Because the satellite launch-market isn't going away, and will probably form the basis of SpaceX's Inco e for DECADES to come (I believe SpaceX will go to Mars someday, but not nearly as quickly as Elon Musk seems to imagine...)

And actually, the manned section of the ITS is basically a giant landable upper stage, with a non-detachable payload.  It shouldn't be drastically different to recover the upper stage and to recover the ITS (indeed a sideways re-entry might be the best one for a reusable upper-stage as well...)

[Grand Ship Builder]

Elon Musk Time (EMT):

Spoiler

Nanosecond = 10 minutes

Millisecond = 10 hours

Second = 10 days

Minute = 100 weeks

Hour = 150 months

Day = 15 years

Week = 5 decades

Month = 20 centuries

Year = 1000 millennia

Decade = 100 million years

Century = 20 billion years

Millennium = 10 googol years

Million years = 100 kjghpillion years

Billion years = basically the end of the universe many times

"It'll be done Soon^tm" = NEVER

[tater]

6 hours ago, Northstar1989 said:

Because the satellite launch-market isn't going away, and will probably form the basis of SpaceX's Inco e for DECADES to come (I believe SpaceX will go to Mars someday, but not nearly as quickly as Elon Musk seems to imagine...)

The satellite launch market will continue to be served by F9 as it is with expendable stage 2, and recoverable fairings. Other launches can be co-manifested on ITSy, which is 100% reusable, obviating any need for developing a reusable F9 stage 2, since they will have a reusable S2 in ITSy itself.

That covers them completely on masses that F9 block 5 can do (approaching initial masses for FH anyway), and heavier stuff for reusable ITSy.

Edited September 22, 2017 by tater

[tater]

 

[Northstar1989]

6 hours ago, tater said:

The satellite launch market will continue to be served by F9 as it is with expendable stage 2, and recoverable fairings. Other launches can be co-manifested on ITSy, which is 100% reusable, obviating any need for developing a reusable F9 stage 2, since they will have a reusable S2 in ITSy itself.

That covers them completely on masses that F9 block 5 can do (approaching initial masses for FH anyway), and heavier stuff for reusable ITSy.

ITSy upper stage isn't designed for commercial satellite launches at all.  Most obviously, it doesn't contain a fairing or deployable cargo bay to anyone's knowledge.  Therefore, whenever it does materialize, it will serve one purpose and one purpose only- sending humans and cargo to the surface of Mars.

Variants for extremely heavy orbital payloads (such as MENTOR, or now LEO station modules) with an alternate upper-stage have been discussed, but such a configuration may never materialize.  And if it DOES, it is likely to take decades to reach flight-test status.

A Falcon Heavy is absolutely necessary for full reusability of both upper and launch stages on many payloads.  The Falcon 9 in expendable mode can only carry 22.8 tons to LEO.  The Falcon Heavy in expendable mode can handle 63.8 tons, so I would imagine it could handle 22.8 tons or close to that with full reusability.

For every ton of fuel, landing legs, etc. you retain on the launch stage of a Falcon 9 for recovery you lose 400 kg of payload, not to mention the lost payliad-capacity from the altered trajectory (more straight-up at first to reduce the boost-back burn to the launchpad).  For every ton retained on the Falcon Heavy's inner core I would imagine it would be 600 kg or more.

But for every ton retained on the UPPER stage of fuel, heat-shielding, fins, landing legs, batteries etc. you lose a ton of payload.  I don't imagine full upper-stage reusability will be possible without a sideways re-entry profile (to decrease maximum re-entry heating and max-Q), grid fins to right it, landing-legs, heat-shielding all over the sides, extra structural reinforcement, and considerable fuel.  I imagine you won't be able to accomplish all that on a FH upper stage without at least 16-18 tons dedicated to upper stage reusability... (the Falcon 9 is probably only capable of carrying 3-4 tons to LEO in fully-reusable mode at most, due to its relatively greater reliance on its upper stage to reach LEO than on the Falcon Heavy, with its 3 stages instead of 2...)

Edited September 22, 2017 by Northstar1989
spelling

[wumpus]

13 hours ago, Northstar1989 said:

With the Falcon Heavy they can achieve FULL reusability for a much wider variety of payloads.  The Falcon Heavy can lift 50 tons to LEO, but 30 tons of that might have to be sacraficed for full reusability of ALL stages...

We have no idea what the requirements for a final stage falcon reuse might be, "all stages" seem premature.

Also don't forget that adding mass to the final stage means that the rest of the rocket has to make up for that delta-v, meaning the center stage has to be staged while going that velocity.  And using up even more mass for returning the last stage means taking even more delta-v from the last stage and making that center booster go even faster.

A lot depends on how much backburn the center booster will require.  For Falcon 9 it was going fairly slow for return (I thought mach 6) for recovered missions and mach 10 for non-recovered missions.  A falcon heavy might recover 3 lower stages while boosting mass that isn't recoverable by the falcon 9, but that means somehow recovering the center booster after it gets going around ~mach 10 (because I'm not expecting any more delta-v from the upper stage).  In KSP you simply add "moar boosters" and be done with it, but Spacex has to deal with rentry heating (and may use quite a backboost to avoid it).

Falcon Heavy recovery (for the center) isn't going to be easy.  I wouldn't be surprised if "half recovery" (the sides recovered, the center and upper expended) will have the cheapest means (at least internally) for spacex to put kg/$ into orbit.  Elon Musk has been downplaying the chances of Falcon Heavy for quite some time.  Most people around here look at the issues of holding 27 engines together.  I suspect that things will get to orbit, but expect the center stage to get overcooked coming home.

I will admit that they should have quite a bit of data on "fast reentering lower stages" from expendable missions and simply tracking the upper booster (I don't think they include paddles.  Maybe they already have the data).  But the problem of landing the center of a Falcon Heavy is a significant step up from the Falcon 9 recovery.

[tater]

@Northstar1989

You have no idea whatsoever what ITSy will or will not look like, so saying it cannot carry sats is untrue. While I am similarly in the dark for the next week, the leaked info suggests an Earth orbital (LEO/BLEO) usage to provide the funding for future missions beyond Earth. This is highly suggestive of use to deliver commercially viable payloads, which in the real world are entirely earth orbiting satellites.

The craft, with or without a crew component as a default, could effectively be what is shown in a few "envisioning" threads on NSF.

[Northstar1989]

1 hour ago, wumpus said:

We have no idea what the requirements for a final stage falcon reuse might be, "all stages" seem premature.

Also don't forget that adding mass to the final stage means that the rest of the rocket has to make up for that delta-v, meaning the center stage has to be staged while going that velocity.  And using up even more mass for returning the last stage means taking even more delta-v from the last stage and making that center booster go even faster.

The Falcon 9 stages are already far more developed than anything used by their competitors.  The difference is, SpaceX has remained dedicated to continuous improvement and refinement of their rocket designs, whereas companies like ULA tend to only refine a design until it works reliably and then freeze it...

As for upper stage reuse- not if you reduce the payload by an equal amount, which I was already *extremely* clear about (raising questions as to how carefully you read my reply before responding).  You cut 1 ton out of payload and add that ton to the upper stage for reusability, leaving the same total mass for the lower stages to accelerate- that was why I referred to the 1:1 tradeoff between payload and upper-stage mass...

Edited September 22, 2017 by Northstar1989
Spelling

[tater]

I get that, my point is that I tend to think that spacex will concentrate on one upper stage for reuse, vs two.

They can concurrently work on a reusable F9 upper stage, and a very different ITSy design, or they can stick with their already mature system and concentrate R&D efforts on ITSy. Like I said, that's what I'm guessing they will do.

That said, they might well follow their pattern and use excess capacity in FH to allow testing with FH stage 2, to the extent it aids ITSy. Should S2 reuse turn out to be easier than expected after such testing, then sure, they pivot and do it.

[Northstar1989]

1 hour ago, wumpus said:

A lot depends on how much backburn the center booster will require.  For Falcon 9 it was going fairly slow for return (I thought mach 6) for recovered missions and mach 10 for non-recovered missions.  A falcon heavy might recover 3 lower stages while boosting mass that isn't recoverable by the falcon 9, but that means somehow recovering the center booster after it gets going around ~mach 10 (because I'm not expecting any more delta-v from the upper stage).  In KSP you simply add "moar boosters" and be done with it, but Spacex has to deal with rentry heating (and may use quite a backboost to avoid it).

Falcon Heavy recovery (for the center) isn't going to be easy.  I wouldn't be surprised if "half recovery" (the sides recovered, the center and upper expended) will have the cheapest means (at least internally) for spacex to put kg/$ into orbit.  Elon Musk has been downplaying the chances of Falcon Heavy for quite some time.  Most people around here look at the issues of holding 27 engines together.  I suspect that things will get to orbit, but expect the center stage to get overcooked coming home.

I will admit that they should have quite a bit of data on "fast reentering lower stages" from expendable missions and simply tracking the upper booster (I don't think they include paddles.  Maybe they already have the data).  But the problem of landing the center of a Falcon Heavy is a significant step up from the Falcon 9 recovery.

No mass is added to the final stage because, once again, any mass reserved for upper stage recovery is removed from payload to keep the total upper stage mass the same (which was already maximized in previpus steps of rocket design if you did it right- there's no real way to increase the mass of the payload+upper stage further without improving engine thrust or ISP...)

As for the upper stage, you should expect *LESS* Delta-V from it on the Falcon Heavy, because it will be roughly the same size as the Falcon 9 upper stage but have more payload atop it.  I would expect the center core will have to boost-back from at least Mach 12- which means *A LOT* of fuel will be required, though still not nearly as much mass as will be needed for upper stage recovery...

This will invariably have to come at the expense of payload, because the more fuel you reserve on the center core, the more Delta-V the upper stage will have to be capable of, and the only way to do that (aside from upgrading its engine further) is to reduce its payload- simply adding more fuel to the upper stage would only make the upper stage heavier,  and require it to cover an even LARGER gap in Delta-V and require more fuel for recovery...

"Moar Boosters" is simply a crude way of expressing the idea of making up for a hit to payload-fraction by launching a larger total rocket.  It ABSOLUTELY still applies in real life, up to a certain degree (lose too much payload-fraction and you won't have any left).

Launching a 16 ton payload to LEO on a Falcon Heavy (capable of 63.8 tons in expendable mode) just so you have enough reserve fuel and can modify each stage enough to enable recovery of all stages is an example of precisely this- you settle for 1/4th the payload-fraction so you can recover and re-use all your stages.  If Elon Musk's predictions about 1/10th the cost for reusability hold true, then this should still be cheaper than a expendable Falcon 9 launch capable of carrying the same 16 ton payload to orbit...

There's absolutely no reason the Falcon Heavy core stage should have to end up being overcooked if you reduce the payload and provide it with enough reserve fuel.

Keep in mind, I don't think Elon Musk will DO THIS on the first Falcon Heavy launch- he will probably push the limits and see if he can recover the core stage under extremely marginal conditions (spoiler: the first time around he probably won't be able to).  But after allowing his engineers to see at what point the core stage becomes nonrecoverable, all he has to do in future launches is direct them to reduce the rated payload capacity enough to give the core adequate reserve fuel for recovery.

With enough reserve fuel, you can give the boost-back burn for the center stage more of an upward component, so it stays above the thickest part of the atmosphere for longer while it has a high lateral velocity, and execute a larger burn at the beginning of re-entry so the maximum re-entry heating is reduced.  With enough reserve fuel, the heat loads on the core stage can be kept within tolerable limits to allow for recovery.

Falcon Heavy core stage recovery might end up taking just as long to figure out as Falcon 9 first stage recovery did.  But the physics absolutely allow for it (upper stage recovery too, with enough mass-budget.  But in practice saving enough mass for this might not leave any mass for payload, making the whole thing irrelevant until the development of orbital fuel depots filled from asteroid-mining or Propulsive Fluid Accumulators...) and I have no doubts it will eventually be accomplished.  Just don't expect it on the first Falcon Heavy launch is all...

Edited September 22, 2017 by Northstar1989

[tater]

Here's a current take on the 9m ITSy:

Orion, Dragon 2, 9m cargo ITSy, original ITS concept, and Shuttle.

The trouble with F9 S2 reuse is that it really does require a brand new S2 design. While I think they can test a number of issues with the current design with smallish changes, mostly related to the entry regime, the actual landing part requires landing motors, gear, etc.

[Northstar1989]

15 hours ago, tater said:

I get that, my point is that I tend to think that spacex will concentrate on one upper stage for reuse, vs two.

They can concurrently work on a reusable F9 upper stage, and a very different ITSy design, or they can stick with their already mature system and concentrate R&D efforts on ITSy. Like I said, that's what I'm guessing they will do.

That said, they might well follow their pattern and use excess capacity in FH to allow testing with FH stage 2, to the extent it aids ITSy. Should S2 reuse turn out to be easier than expected after such testing, then sure, they pivot and do it.

SpaceX doesn't have remotely near the capital available to it to develop the ITSy upper stage just yet.  It's not just a matter of focus or logistics- they simply don't have enough available funding to finish the ITSy design if they begin it right now.

Which is why I think they will focus most of their efforts on the Falcon Heavy and reusability (of both upper and lower stages- they still haven't got launch stsge turnaround-times and refurbishment costs down to where they need to be...) for now.  If they are SUCCESSFUL in not only launching a Falcon Heavy, but in eventually learning to recover all its stages, then I think there will be a lot more government and investor-confidence to invest in the ITSy.   They also need to demonstrate they can successfully launch human crews to orbit, and recover them safely, with the Dragon 2 before public and private partners/investors are even remotely likely to provide the funding to develop the ITSy...

14 hours ago, tater said:

Here's a current take on the 9m ITSy:

Orion, Dragon 2, 9m cargo ITSy, original ITS concept, and Shuttle.

The trouble with F9 S2 reuse is that it really does require a brand new S2 design. While I think they can test a number of issues with the current design with smallish changes, mostly related to the entry regime, the actual landing part requires landing motors, gear, etc.

I agree, final stage reusability will ABSOLUTELY require a re-design of significant parts of the upper stage.  In particular, they will need to add landing-legs, grid fins, heat-shielding, sensors, and more advanced guidance systems.  The Merlin engine is already throttleable down to 60%, but I suspect they will also need the 20% throttling that the Raptor is supposed to be capable of (which will also require a re-design of the upper stage to run on Liquid Methane and LOX instead of RP-1 and LOX...)

However all this is even more reason why they need to get started on all this now- because they have a lot of work to do to enable upper stage recovery, and the potential economic rewards are MILLIONS of dollars in cost-savings on each launch.  Successfully completing such a mammoth undertaking as upper stage re-use (remember, except for the Shuttle it has never been done before) will also be an excellent way of building public/private investor confidence that they can successfully build the ITSy...

Speaking of the Raptor engine, has anyone heard any news about it recently?  I heard hints that it might be capable of even better performance than previously anticipated by the final design...

Edited September 23, 2017 by Northstar1989

[tater]

They also will almost certainly not have a mixed propellant rocket, so I don't see raptor as a F9 US.

I think ITSy is far more doable soon than the ITS concept, and I also bet that the AF has some interest as well.  We'll know in a week.

[Northstar1989]

15 minutes ago, tater said:

They also will almost certainly not have a mixed propellant rocket, so I don't see raptor as a F9 US.

You have no basis for that assertion at all- SpaceX has already openly considered deploying the Raptor as an alternative upper stage engine for the Falcon 9 to fulfill an Air Force tech development program's requirements for advanced upper stage propulsion with alternative fuels (interestingly, testing a new engine on a suborbital trajectory like this is about as close to a KSP part contract as the real world ever comes...)  and it's not like there is any fuel-crossfeed between the upper and lower stages that would prevent them from developing a rocket with different upper and lower stage propellants...

Edited September 22, 2017 by Northstar1989

[sevenperforce]

8 minutes ago, Northstar1989 said:

You have no basis for that assertion at all- SpaceX has already openly considered deploying the Raptor as an alternative upper stage engine for the Falcon 9 to fulfill an Air Force tech development program's requirements for advanced upper stage propulsion with alternative fuels (interestingly, testing a new engine on a suborbital trajectory like this is about as close to a KSP part contract as the real world ever comes...)  and it's not like there is any fuel-crossfeed between the upper and lower stages that would prevent them from developing a rocket with different upper and lower stage propellants...

That's what I thought too, initially, but I have it on good authority from someone in Cape Canaveral (and I don't mean a tourist) that SpaceX absolutely will not cross-plumb its F9 or FH launch pads. 

The contract with the Air Force was to obtain funding to develop an alternative-fuel upper-stage engine that COULD be used on F9. There was no obligation to actually test or deploy it.

48 minutes ago, Northstar1989 said:

Final stage reusability will ABSOLUTELY require a re-design of significant parts of the upper stage.  In particular, they will need to add landing-legs, grid fins, heat-shielding, sensors, and more advanced guidance systems.  The Merlin engine is already throttleable down to 60%, but I suspect they will also need the 20% throttling that the Raptor is supposed to be capable of (which will also require a re-design of the upper stage to run on Liquid Methane and LOX instead of RP-1 and LOX...)

All the F9 upper stage really needs is a heat shield, something to stabilize it during re-entry, and chutes, and it can splash down and float, which is technically "recovery". That's what I suspect Elon is thinking of when he talks about setting up the FH inaugural launch for reuse.

[tater]

I've heard the same thing regarding 39A and SLC-40 plumbing. I cannot speak for other locations (Boca Chica?).

Another important point is that Merlin has been remarkably improved over its versions to the point that possible benefit from Raptor as an US is perhaps not so great, particularly given the need for bigger tanks, which makes any such design completely novel.

This is important, because SpaceX is tooled for F9 diameter now, and will presumably retool for their next diameter (up to 9m) for ITSy, even if the later is tooling for composites vs aluminum. If they manage the fairing recovery problem, then the waste on S2 is an even smaller % of total cost---and they are already incredibly cheap.

In addition, mass is not everything, volume matters. It's important to keep an eye on the next big rocket coming along, NG, with a 7m fairing. This vehicle is an existential threat to SLS, honestly, and if it indeed flies in 2020, will put BO in a superior position for some payloads, even with a lower delivered mass to LEO. ITSy seems like something they would want to see in a timeframe of early NG availability, IMO.

[sevenperforce]

12 minutes ago, tater said:

I've heard the same thing regarding 39A and SLC-40 plumbing. I cannot speak for other locations (Boca Chica?).

Another important point is that Merlin has been remarkably improved over its versions to the point that possible benefit from Raptor as an US is perhaps not so great, particularly given the need for bigger tanks, which makes any such design completely novel.

This is important, because SpaceX is tooled for F9 diameter now, and will presumably retool for their next diameter (up to 9m) for ITSy, even if the later is tooling for composites vs aluminum. If they manage the fairing recovery problem, then the waste on S2 is an even smaller % of total cost---and they are already incredibly cheap.

In addition, mass is not everything, volume matters. It's important to keep an eye on the next big rocket coming along, NG, with a 7m fairing. This vehicle is an existential threat to SLS, honestly, and if it indeed flies in 2020, will put BO in a superior position for some payloads, even with a lower delivered mass to LEO. ITSy seems like something they would want to see in a timeframe of early NG availability, IMO.

Note that although NG's base diameter is 7 meters, its initial fairing looks like it will be 5 meters. The 7-meter NG will be the three-stage variant, which will probably fly later.

I would love to see a 5-meter mini-Raptor upper stage for the Falcon 9 and Falcon Heavy, potentially with an enlarged reusable cargo bay, but without cross-plumbing it simply won't happen.

[tater]

No, they dumped the 5m fairing last week or two, 7m from day one, 2-stage version.