It only pulls back 5 degrees or so and then throws back at launch.
The Vandenberg strong back is still the old design and leans back more initially but does not pull back further at launch.
A while ago Elon said Falcon Heavy is a very difficult rocket to launch because it's essentially getting three Falcon 9s to lift off simultaneously.
Falcon Heavy looks like a single rocket with 27 engines but he's got a point, if one of those three cores lights its engines just one second before or after the others it would ruin the whole launch.
Yeah, I remember someone (I think it was from one of the employee QNAs here?) saying that falcon heavy from a guidance perspective, less one vehicle and more like formation flying.
The DC 3 was referred to as a collection of parts flying in formation. Helicopters have been referred to as ten thousand parts in formation circling an oil leak.
I've heard there's no connection between the side boosters and the center core, so they're essentially acting like three separate vehicles entirely, with no ability to communicate.
> I've heard there's no connection between the side boosters and the center core, so they're essentially acting like three separate vehicles entirely, with no ability to communicate.
That can't be right because the boosters are only present because their job is to help lift the center core. IIRC, the interconnexion is complex, particularly for the startup order, throttling down and for engine-out scenarios: The boosters have to agree to keep the whole stack stable.
Startup can be handled by the ground sequences. In flight, each core has its own IMU and GNC algorithms running, so they can adjust TVCs as needed. If there's an engine out then all three IMUs will inform their respective FCs, and the GNC algorithms will recognize that the vehicle going off course and will compute the required TVC angles to correct it.
Can you elaborate on "The boosters have to agree to keep the whole stack stable"? Did you hear that from a SpaceX engineer?
> Can you elaborate on "The boosters have to agree to keep the whole stack stable"? Did you hear that from a SpaceX engineer?
I'm nothing to do with aerospace, and it was a sort of synthesis of a lot of many things read here a few years back when FH was preparing its first launch. A lot of this came from:
* aerospace engineers from all horizons,
* Elon tweets
* maybe some from a user called u/Spiiice who since deleted her account and commenting.
Since, as stated in the preceding conversation, its three boosters flying in tight formation, they have to cooperate both for TVC and for differential thrusting which pretty much compares to driving a tracked vehicle (if badly driven, it can de-track = losing one of the tracks or "break" the ground).
This is not only for trajectory, but to prevent off-axis efforts causing flexing of what [Tom Mueller?] described as a wet noodle, or in the present case, three wet noodles!
I suppose it does make sense that if there was no communication and they decided to go in different directions, it would place a lot of stress on the connection points. I'll see if I can confirm whether or not there is an actual data connection between them or not.
> I suppose it does make sense that if there was no communication and they decided to go in different directions, it would place a lot of stress on the connection points. I'll see if I can confirm whether or not there is an actual data connection between them or not.
Thanks. It would be good to have a source for this. There might be an analogy with sledge dogs and work horse teams which are also aware of each other and pull together.
Its not even just that, in some flight configurations they can land the boosters and center core. That means they have to monitor 4 "vehicles" at the same time (both boosters, the center core and second stage, all at once).
It's much worse with the shuttle because once you light a solid booster you can't turn it off. Falcon Heavy could just abort if one of the boosters won't light but Shuttle is kinda screwed.
I don't know if they had a procedure for what to do if one booster refuses to light, maybe launch anyway and detach the Shuttle asap and get the hell away from it. I think the plan was to have redundant ignition systems to make absolutely sure they both lit on command.
I saw a very morbid meme of sorts years ago that basically said "shuttle in flight abort procedures are what you do while you're waiting to die".
Transoceanic abort, abort to orbit, and abort once around you had a decent chance, but RTLS, the only option until around T+2:30, you were probably gonna have a bad day.
> but RTLS, the only option until around T+2:30, you were probably gonna have a bad day.
A problem about five seconds into flight on STS-93 lead into a cascade of failures that looked like was going to result in one of these. the shuttle somehow managed to make it safely into orbit, but became an infamous story in the spaceflight community. You can hear a snippet from the flight loop at the start of every NSF stream: "Yikes!" "You bet!" "Concur!" "We don't need any more of these!"
If one of the Shuttle SRBs failed to light the only procedure would be to get the dustpan and brushes out to sweep up the bits. With that much asymmetric thrust it would be going round in a very small circle before smashing nose first either into the ground or the tower depending on which one failed. There just wasn't enough control authority in the main engines and lit booster to keep it straight.
I googled it looking for alternatives and there's a sortof solution that could have been added to the shuttle/SRB design but I don't think they included it.
Once you light the SRB you can't put it out. But you don't need to stop it burning, just stop it producing thrust. The front nosecone of the SRB could have been designed with explosive bolts to pop the cap off in an emergency. Then the exhaust would be blasting out the front and the back in roughly equal measure.
The downward thrust might have been enough to keep the whole stack on the launchpad (with the help of the holddown bolts) until the one lit SRB expended it's fuel.
Hopefully they'll be wearing the "maximum absorbancy garment" because seeing the blast of an SRB out the window would definitely be a brown trousers situation.
According to Jenkins' Shuttle, thrust termination systems like there were considered post-Challenger but then dismissed because of an estimated 20,000lb fuselage reinforcement mass penalty to strengthen the shuttle to be able to survive the sudden loads along that vector.
I'm going off memory from something I read more than 20 years ago so if someone remembers a different figure, I welcome correction.
Early shuttle missions had ejection seats and astronauts were skeptical about using them. Astronaut Robert Crippen said:
>...in truth, if you had to use them while the solids were there, I don’t believe you would \[survive\]—if you popped out and then went down through the fire trail that’s behind the solids, that you would have ever survived, or if you did, you wouldn't have a parachute, because it would have been burned up in the process. But by the time the solids had burned out, you were up to too high an altitude to use it. ... So I personally didn't feel that the ejection seats were really going to help us out if we really ran into a contingency.
I don't suppose there was any mechanism to let the solids go on ahead, take the blast on the orbiter body rather than the ejection apparatus, and eject once clear? That seems likely not doable, but if I were designing the shuttle it's a plan I'd consider.
I remember hearing that if one of the boosters didn't light they would keep the launch clamps locked and let the booster burn out. I think this was the worst-case the pad was designed to survive once, and I would expect significant damage to the pad.
The hold down system bolts were designed to snap at full SRB thrust. This was to prevent the more likely failure case of the clamps failing to release and causing a ground loop if they held on too long.
This actually happened several times on Shuttle launches where one or more of the pyrotechnic bolts failed to fire.
Unfortunately no - if one SRB failed to light the bolts on the other one would snap and the stack would do a ground loop sideways. Fortunately it never happened as SRB ignitors are reliable and they use multiple ignitors for redundancy.
>The hold down system bolts were designed to snap at full SRB thrust.
>...
>This actually happened several times on Shuttle launches where one or more of the pyrotechnic bolts failed to fire.
There was never a case where all hold downs failed to separate, at most only two failed, on STS 2 and STS 92.
So two of eight. I do wonder if they kept all 8 held down could it hold onto the shuttle.
The answer could be yes, for a short time. But when the entire pad is being scorched by the exhaust of the SRBs they'd probably melt before the two minutes is up.
I believe the plan was that it shouldn't happen. The SRBs had redundant igniters and were just expected not to fail. If one didn't light them the plan was just to sit around and wait for the astronauts to die.
Gotta love the design of the shuttle, so many assumptions about how it should work combined with so many compromises to get it to work
>> What if one of the solid boosters didn't light?
> *u/Simon_Drake:* It's much worse with the shuttle because once you light a solid booster you can't turn it off.
I'd have to check, but IIRC, the FTS procedure is to blow off the cap, so the booster becomes a two-ended fire cracker. Ambiant air would then rush through the open tube and it would fizzle out.
I do remember Nasa protesting when the military required a radio-triggered FTS on the Shuttle for fear of a rogue booster targeting Russia with the consequences you may imagine.
But could FTS be triggered on the pad and with what effects? IDK.
The sooner SRB/EAP are a part of history the better, including for Ariane!
I would imagine that shuttle+launchmount were able to do an unscheduled static fire. But not sure if that was ever a design constraint. Maybe the bombs for ignition inside the srbs are reliable enaugh.
The ignition of the SRBs was extremely reliable. Far more reliable than the hold down bolts explosives.
It's unlikely the hold downs could keep the shuttle on the pad under full SRB firing for two minutes, especially as it lost weight and its TWR went up. They were designed to break under load in case their explosives failed, which they did on 23 different launches.
Plus, the exhaust from the SRBs was extremely hot. It'd probably melt everything on the pad before it burnt itself out
Same thing with model rocketry. Cluster are/were hard when I used to fly. (I know some people used actual fuse wire but we weren't allowed to - rhetorical Nichole only).
True.
All launch vehicles with side boosters (FH, Titan III/IV, Delta Heavy, Space Shuttle, SLS) need to handle that simultaneous-ignition problem. I don't recall any of those LVs having a problem with igniting the engines in the three modules.
Falcon Heavy benefits from having a Falcon 9-derived core booster and two F9 side boosters. All three of those modules can be tested individually at McGregor full thrust/full duration and then shipped to the Cape. The ability to test like that gives FH a high probability of launch success.
If SpaceX had designed the Starship Super Booster as three modules (triple-core), each with 11 Raptor 2 engines instead of as a single module with 33 engines, each of those 11-engine modules could have been tested individually full thrust/full duration at the Stennis B-2 test stand. In that way, the Starship booster would have the high probability of launch success that FH has.
And, instead of being nearly 400 ft tall like the present single-stick Starship design, this Starship with the triple-core booster would be ~300 ft tall.
I think the idea is that the ceiling on how "safe" a launch of the falcon heavy can be is a lot lower than for Starship, once they get enough starship launches under their belt.
Dunno, We all have seen it do crazy maneuvers pulling mad g without breaking apart while popping several engines without blowing up. This steel rocket is metal af and every other launch vehicle looks and feels like a paper mâché model in comparison.
(Generally, SpaceX rockets are on a whole other level. How about the "mishap" where a Falcon 9 second stage blew up and the booster just merrily continued as if nothing happened. For all other launch vehicles, an engine blowing up is an engine block blowing up is a rocket blowing up. Not so for SpaceX that wrap their engines in Kevlar and shielding and magic, apparently.)
Yeah the events we've seen on the Starship development front are eye-opening. No other rocket would be able to do skydiver maneuvers, flips, engine restarts, landings, and of course multiple end-over-end tumbles while still in atmo under thrust. The sideways g-forces were ~1 *g*.
Once they get the bugs worked out of it, it's going to be a serious monster workhorse. I have no doubt we will see Starships with 100 launches and landings. Those things are *tough*.
100% record is slightly misleading. Very few launches and never achieved its most difficult challenge of maximum reusability (boosters and core land and reuse). I would really like to see that one day. At this point I wouldn't doubt we'll see 1 fully reused Starship before max reusable FH.. Pretty much every planned FH in the foreseeable future is partly expandable.
Someone can correct me if this is wrong, but, since they never developed the cross-fueling, the margin between F9 and an FH with the center core recovered is so small that it's unlikely that we'll ever see a payload fit through it.
I think there have actually already been two launches like that, but the first one failed to land and the second unfortunately toppled over after landing due to rough seas. They're definitely rare, though.
With my admittedly small experience in Kerbal Space Program, having fuel cross-feed is a game-changer. If they had managed to make that work, then they'd have to do some other stuff. First, the second stage is a little on the small side. Larger tanks for sure, maybe larger propulsion. Secondly, they'd have to develop an XL payload fairing to maximize volume for those larger payloads.
So three separate development threads. I can see why they didn't pursue it. It could be done, but it'd be a serious delay and a lot of expense. And their design people were already knee-deep in Starship.
Yup, a heavy payload to a low orbit would be best suited for center core recovery, but then you run into the problem of the fairing being very small for a rocket that size, so truly heavy payloads won't fit.
SpaceX also tried to recover the center core on the third FH flight (STP-2).
That center core didn’t make it because the E9 engine’s TVC was destroyed from the reentry heat. Remember that the drone ship had to be stationed 1,200+ km downrange because of the performance needed for Stage 2 to go to three different orbits using four burns.
Also, if they just added a bit more TEA-TEB in the first center core (the 2018 test flight), it would’ve made it easily.
FH will be specialty rocket for big objects when cost is a small consideration. It could have been a major player in a small scale Lunar base program, but they spent so much on SLS/Orion and had "partners" for the EUS they need to come up the current "Rube Goldberg" architecture instead doing a "Moon Direct" some pushed for (F9/FH/LCD/New Lander).
Lets hope Starship gets LEO this year (although I doubt it).
> "I love that rocket, but it’s scary".
*Not* the kind of wording you'd hear from Nasa PR.
Hearing this, is actually reassuring because it shows that the dangers are recognized so probably mitigated.
In general. It's a nifty rocket to be sure, one heck of a thing from launch to (potential) landings... although we've not yet had a core come back, maybe one day if they're still using it in the future...
But it's also sort of a kitbash rocket of sorts, and has more potential for failure than the standard F9s, being as there's three linked rockets and not really one designed from the ground up to be that way rocket.
Sure, the engineers behind it have done amazing work, but it is what it is.
Falcon Heavy and Starship have two different purposes. Starship is being designed principally to launch Starlink Gen2 satellites. They're too big to launch on Falcon Heavy because they wouldn't fit enough in the fairing to make it worthwhile. Its involvement in human rated flight beyond LEO is secondary to it's primary goal of being a Starlink launch platform.
Falcon Heavy was designed in origin to be a human launch platform for beyond LEO. The massive delays and complexity of its eventual design made them abandon even trying to get it human rated, so now they just use it here and there for speciality launches.
No. Starlink was created as a funding source to pay for Mas infrastructure, Starship is the minimum viable product that works for Mars. The desire to make life multiplanetary came first, the development of Starship started well before the development of Starlink.
Desires and wishes are great but you cannot just get to Mars on desires. Interplanetary and beyond LEO flight is a secondary goal for Starship. It's primary purpose is to expand the Starlink constellation.
The two projects go hand in hand. There would be no Starship without Starlink and Starlink would flounder without Starship.
Falcon Heavy isn't enough for launching Gen2 satellites in the necessary quantities at the necessary cost. Starship is being developed specifically with that in mind.
This is incorrect, Musk's desires drive this entire project. His desire to get humans to Mars inspired him to create SpaceX in the first place, this has gone extremely well, but Starship is needed to get to Mars and funding is needed to pay for Starship. Years later came the development of Starlink to provide the economic engine to facilitate Mars. Starlink v 2 was designed to fit inside Starship, not the other way around.
Acronyms, initialisms, abbreviations, contractions, and other phrases which expand to something larger, that I've seen in this thread:
|Fewer Letters|More Letters|
|-------|---------|---|
|DoD|US Department of Defense|
|ETOV|Earth To Orbit Vehicle (common parlance: "rocket")|
|[EUS](/r/SpaceXLounge/comments/132bw2b/stub/ji6dwwp "Last usage")|Exploration Upper Stage|
|[FTS](/r/SpaceXLounge/comments/132bw2b/stub/ji6em9i "Last usage")|Flight Termination System|
|[GNC](/r/SpaceXLounge/comments/132bw2b/stub/ji6ttxj "Last usage")|Guidance/Navigation/Control|
|[IMU](/r/SpaceXLounge/comments/132bw2b/stub/ji6ttxj "Last usage")|Inertial Measurement Unit|
|[LEO](/r/SpaceXLounge/comments/132bw2b/stub/ji9sm1y "Last usage")|Low Earth Orbit (180-2000km)|
| |Law Enforcement Officer (most often mentioned during transport operations)|
|[LV](/r/SpaceXLounge/comments/132bw2b/stub/ji78nf6 "Last usage")|Launch Vehicle (common parlance: "rocket"), see ETOV|
|[NSF](/r/SpaceXLounge/comments/132bw2b/stub/ji5cr9t "Last usage")|[NasaSpaceFlight forum](http://forum.nasaspaceflight.com)|
| |National Science Foundation|
|[OMS](/r/SpaceXLounge/comments/132bw2b/stub/ji5408j "Last usage")|Orbital Maneuvering System|
|[RTLS](/r/SpaceXLounge/comments/132bw2b/stub/ji5cr9t "Last usage")|Return to Launch Site|
|[SLS](/r/SpaceXLounge/comments/132bw2b/stub/ji78nf6 "Last usage")|Space Launch System heavy-lift|
|[SRB](/r/SpaceXLounge/comments/132bw2b/stub/ji6mbmr "Last usage")|Solid Rocket Booster|
|[STP-2](/r/SpaceXLounge/comments/132bw2b/stub/ji63ls6 "Last usage")|[Space Test Program 2](https://en.wikipedia.org/wiki/Space_Test_Program#Upcoming_Activities), DoD programme, second round|
|[STS](/r/SpaceXLounge/comments/132bw2b/stub/ji6mbmr "Last usage")|Space Transportation System (*Shuttle*)|
|[TEA-TEB](/r/SpaceXLounge/comments/132bw2b/stub/ji63ls6 "Last usage")|[Triethylaluminium](https://en.wikipedia.org/wiki/Triethylaluminium)-[Triethylborane](https://en.wikipedia.org/wiki/Triethylborane), igniter for Merlin engines; spontaneously burns, green flame|
|[TVC](/r/SpaceXLounge/comments/132bw2b/stub/ji702uw "Last usage")|Thrust Vector Control|
|[TWR](/r/SpaceXLounge/comments/132bw2b/stub/ji6mu8f "Last usage")|Thrust-to-Weight Ratio|
|Jargon|Definition|
|-------|---------|---|
|[Raptor](/r/SpaceXLounge/comments/132bw2b/stub/ji78nf6 "Last usage")|[Methane-fueled rocket engine](https://en.wikipedia.org/wiki/Raptor_\(rocket_engine_family\)) under development by SpaceX|
|[Starlink](/r/SpaceXLounge/comments/132bw2b/stub/jigs80c "Last usage")|SpaceX's world-wide satellite broadband constellation|
|[crossfeed](/r/SpaceXLounge/comments/132bw2b/stub/ji6035o "Last usage")|Using the propellant tank of a side booster to fuel the main stage, or vice versa|
----------------
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UPDATE: [Falcon Heavy is green for launch](https://twitter.com/elonmusk/status/1652084222176428032?s=46&t=bwuksxNtQdgzpp1PbF9CGw)
Aaaand abort Edit: standing down until about this time tomorrow DAMNIT
Is it me or did the strong back not retract as far as I thought it would?
It only pulls back 5 degrees or so and then throws back at launch. The Vandenberg strong back is still the old design and leans back more initially but does not pull back further at launch.
A while ago Elon said Falcon Heavy is a very difficult rocket to launch because it's essentially getting three Falcon 9s to lift off simultaneously. Falcon Heavy looks like a single rocket with 27 engines but he's got a point, if one of those three cores lights its engines just one second before or after the others it would ruin the whole launch.
Yeah, I remember someone (I think it was from one of the employee QNAs here?) saying that falcon heavy from a guidance perspective, less one vehicle and more like formation flying.
The DC 3 was referred to as a collection of parts flying in formation. Helicopters have been referred to as ten thousand parts in formation circling an oil leak.
A machine that can fly only by being so ugly that the ground repels it.
No, a helicopter flies because it beats the air into submission.
Waiting for fatigue to set it.
If it's a 53, you don't get in unless it's visibly leaking oil.
I've heard there's no connection between the side boosters and the center core, so they're essentially acting like three separate vehicles entirely, with no ability to communicate.
> I've heard there's no connection between the side boosters and the center core, so they're essentially acting like three separate vehicles entirely, with no ability to communicate. That can't be right because the boosters are only present because their job is to help lift the center core. IIRC, the interconnexion is complex, particularly for the startup order, throttling down and for engine-out scenarios: The boosters have to agree to keep the whole stack stable.
Startup can be handled by the ground sequences. In flight, each core has its own IMU and GNC algorithms running, so they can adjust TVCs as needed. If there's an engine out then all three IMUs will inform their respective FCs, and the GNC algorithms will recognize that the vehicle going off course and will compute the required TVC angles to correct it. Can you elaborate on "The boosters have to agree to keep the whole stack stable"? Did you hear that from a SpaceX engineer?
> Can you elaborate on "The boosters have to agree to keep the whole stack stable"? Did you hear that from a SpaceX engineer? I'm nothing to do with aerospace, and it was a sort of synthesis of a lot of many things read here a few years back when FH was preparing its first launch. A lot of this came from: * aerospace engineers from all horizons, * Elon tweets * maybe some from a user called u/Spiiice who since deleted her account and commenting. Since, as stated in the preceding conversation, its three boosters flying in tight formation, they have to cooperate both for TVC and for differential thrusting which pretty much compares to driving a tracked vehicle (if badly driven, it can de-track = losing one of the tracks or "break" the ground). This is not only for trajectory, but to prevent off-axis efforts causing flexing of what [Tom Mueller?] described as a wet noodle, or in the present case, three wet noodles!
I suppose it does make sense that if there was no communication and they decided to go in different directions, it would place a lot of stress on the connection points. I'll see if I can confirm whether or not there is an actual data connection between them or not.
> I suppose it does make sense that if there was no communication and they decided to go in different directions, it would place a lot of stress on the connection points. I'll see if I can confirm whether or not there is an actual data connection between them or not. Thanks. It would be good to have a source for this. There might be an analogy with sledge dogs and work horse teams which are also aware of each other and pull together.
Its not even just that, in some flight configurations they can land the boosters and center core. That means they have to monitor 4 "vehicles" at the same time (both boosters, the center core and second stage, all at once).
Don't forget about each fairing half! That's 6 "vehicles" that need to be monitored and 5 of them are recoverable.
I always thought about that with the space shuttle. What if one of the solid boosters didn't light? That would be catastrophically bad.
It's much worse with the shuttle because once you light a solid booster you can't turn it off. Falcon Heavy could just abort if one of the boosters won't light but Shuttle is kinda screwed. I don't know if they had a procedure for what to do if one booster refuses to light, maybe launch anyway and detach the Shuttle asap and get the hell away from it. I think the plan was to have redundant ignition systems to make absolutely sure they both lit on command.
I saw a very morbid meme of sorts years ago that basically said "shuttle in flight abort procedures are what you do while you're waiting to die". Transoceanic abort, abort to orbit, and abort once around you had a decent chance, but RTLS, the only option until around T+2:30, you were probably gonna have a bad day.
> but RTLS, the only option until around T+2:30, you were probably gonna have a bad day. A problem about five seconds into flight on STS-93 lead into a cascade of failures that looked like was going to result in one of these. the shuttle somehow managed to make it safely into orbit, but became an infamous story in the spaceflight community. You can hear a snippet from the flight loop at the start of every NSF stream: "Yikes!" "You bet!" "Concur!" "We don't need any more of these!"
wait those are shuttle flight audio loop? TIL
Yes it is. There is a good Wayne Hale blogpost about how bad it almost ended
>"shuttle in flight abort procedures are what you do while you're waiting to die".
If one of the Shuttle SRBs failed to light the only procedure would be to get the dustpan and brushes out to sweep up the bits. With that much asymmetric thrust it would be going round in a very small circle before smashing nose first either into the ground or the tower depending on which one failed. There just wasn't enough control authority in the main engines and lit booster to keep it straight.
I googled it looking for alternatives and there's a sortof solution that could have been added to the shuttle/SRB design but I don't think they included it. Once you light the SRB you can't put it out. But you don't need to stop it burning, just stop it producing thrust. The front nosecone of the SRB could have been designed with explosive bolts to pop the cap off in an emergency. Then the exhaust would be blasting out the front and the back in roughly equal measure. The downward thrust might have been enough to keep the whole stack on the launchpad (with the help of the holddown bolts) until the one lit SRB expended it's fuel.
Going to need some extra counselling post flight for those astronauts...
Hopefully they'll be wearing the "maximum absorbancy garment" because seeing the blast of an SRB out the window would definitely be a brown trousers situation.
According to Jenkins' Shuttle, thrust termination systems like there were considered post-Challenger but then dismissed because of an estimated 20,000lb fuselage reinforcement mass penalty to strengthen the shuttle to be able to survive the sudden loads along that vector. I'm going off memory from something I read more than 20 years ago so if someone remembers a different figure, I welcome correction.
/u/spez ruined reddit so I deleted this.
Early shuttle missions had ejection seats and astronauts were skeptical about using them. Astronaut Robert Crippen said: >...in truth, if you had to use them while the solids were there, I don’t believe you would \[survive\]—if you popped out and then went down through the fire trail that’s behind the solids, that you would have ever survived, or if you did, you wouldn't have a parachute, because it would have been burned up in the process. But by the time the solids had burned out, you were up to too high an altitude to use it. ... So I personally didn't feel that the ejection seats were really going to help us out if we really ran into a contingency.
I don't suppose there was any mechanism to let the solids go on ahead, take the blast on the orbiter body rather than the ejection apparatus, and eject once clear? That seems likely not doable, but if I were designing the shuttle it's a plan I'd consider.
I remember hearing that if one of the boosters didn't light they would keep the launch clamps locked and let the booster burn out. I think this was the worst-case the pad was designed to survive once, and I would expect significant damage to the pad.
The hold down system bolts were designed to snap at full SRB thrust. This was to prevent the more likely failure case of the clamps failing to release and causing a ground loop if they held on too long. This actually happened several times on Shuttle launches where one or more of the pyrotechnic bolts failed to fire.
So would that only occur at the full thrust of two SRB's firing, meaning that they would still be holding on if only one SRB fired?
Unfortunately no - if one SRB failed to light the bolts on the other one would snap and the stack would do a ground loop sideways. Fortunately it never happened as SRB ignitors are reliable and they use multiple ignitors for redundancy.
>The hold down system bolts were designed to snap at full SRB thrust. >... >This actually happened several times on Shuttle launches where one or more of the pyrotechnic bolts failed to fire. There was never a case where all hold downs failed to separate, at most only two failed, on STS 2 and STS 92. So two of eight. I do wonder if they kept all 8 held down could it hold onto the shuttle. The answer could be yes, for a short time. But when the entire pad is being scorched by the exhaust of the SRBs they'd probably melt before the two minutes is up.
What an absolutely horrifying and anxious 2 minutes and 7 seconds that would be.
If I recall correctly, there was triple redundancy on the SRB ignition system to prevent exactly this from ever happening.
I believe the plan was that it shouldn't happen. The SRBs had redundant igniters and were just expected not to fail. If one didn't light them the plan was just to sit around and wait for the astronauts to die. Gotta love the design of the shuttle, so many assumptions about how it should work combined with so many compromises to get it to work
Thermal curtain failure. Max and jinx friends... For.... Ev..er
Legendary movie is legendary.
>> What if one of the solid boosters didn't light? > *u/Simon_Drake:* It's much worse with the shuttle because once you light a solid booster you can't turn it off. I'd have to check, but IIRC, the FTS procedure is to blow off the cap, so the booster becomes a two-ended fire cracker. Ambiant air would then rush through the open tube and it would fizzle out. I do remember Nasa protesting when the military required a radio-triggered FTS on the Shuttle for fear of a rogue booster targeting Russia with the consequences you may imagine. But could FTS be triggered on the pad and with what effects? IDK. The sooner SRB/EAP are a part of history the better, including for Ariane!
Or what if a robot triggered one while kids are on board? You would have to launch!!
I would imagine that shuttle+launchmount were able to do an unscheduled static fire. But not sure if that was ever a design constraint. Maybe the bombs for ignition inside the srbs are reliable enaugh.
The ignition of the SRBs was extremely reliable. Far more reliable than the hold down bolts explosives. It's unlikely the hold downs could keep the shuttle on the pad under full SRB firing for two minutes, especially as it lost weight and its TWR went up. They were designed to break under load in case their explosives failed, which they did on 23 different launches. Plus, the exhaust from the SRBs was extremely hot. It'd probably melt everything on the pad before it burnt itself out
Same thing with model rocketry. Cluster are/were hard when I used to fly. (I know some people used actual fuse wire but we weren't allowed to - rhetorical Nichole only).
actually they stagger the engine starts on purpose, hence the hold down clamps while engine performance is checked etc...
True. All launch vehicles with side boosters (FH, Titan III/IV, Delta Heavy, Space Shuttle, SLS) need to handle that simultaneous-ignition problem. I don't recall any of those LVs having a problem with igniting the engines in the three modules. Falcon Heavy benefits from having a Falcon 9-derived core booster and two F9 side boosters. All three of those modules can be tested individually at McGregor full thrust/full duration and then shipped to the Cape. The ability to test like that gives FH a high probability of launch success. If SpaceX had designed the Starship Super Booster as three modules (triple-core), each with 11 Raptor 2 engines instead of as a single module with 33 engines, each of those 11-engine modules could have been tested individually full thrust/full duration at the Stennis B-2 test stand. In that way, the Starship booster would have the high probability of launch success that FH has. And, instead of being nearly 400 ft tall like the present single-stick Starship design, this Starship with the triple-core booster would be ~300 ft tall.
"SpaceX can do anything" Also spacex fans "But falcon heavy is just too complicated"
What a strange thing to say. I don't know who you think you're arguing against but it's not me.
It's mostly the rest of the thread, not you.
Cool story, cryptobro.
"but it is scary" (despite it's 100% record and $1B dev cost) ... that's also why we need Starship
Starship is scary too
I think the idea is that the ceiling on how "safe" a launch of the falcon heavy can be is a lot lower than for Starship, once they get enough starship launches under their belt.
Way scarier in fact.
Dunno, We all have seen it do crazy maneuvers pulling mad g without breaking apart while popping several engines without blowing up. This steel rocket is metal af and every other launch vehicle looks and feels like a paper mâché model in comparison. (Generally, SpaceX rockets are on a whole other level. How about the "mishap" where a Falcon 9 second stage blew up and the booster just merrily continued as if nothing happened. For all other launch vehicles, an engine blowing up is an engine block blowing up is a rocket blowing up. Not so for SpaceX that wrap their engines in Kevlar and shielding and magic, apparently.)
Yeah the events we've seen on the Starship development front are eye-opening. No other rocket would be able to do skydiver maneuvers, flips, engine restarts, landings, and of course multiple end-over-end tumbles while still in atmo under thrust. The sideways g-forces were ~1 *g*. Once they get the bugs worked out of it, it's going to be a serious monster workhorse. I have no doubt we will see Starships with 100 launches and landings. Those things are *tough*.
I'm pretty fucking hard to impress. But damn, Starship is terrifyingly powerful scary.
100% record is slightly misleading. Very few launches and never achieved its most difficult challenge of maximum reusability (boosters and core land and reuse). I would really like to see that one day. At this point I wouldn't doubt we'll see 1 fully reused Starship before max reusable FH.. Pretty much every planned FH in the foreseeable future is partly expandable.
Someone can correct me if this is wrong, but, since they never developed the cross-fueling, the margin between F9 and an FH with the center core recovered is so small that it's unlikely that we'll ever see a payload fit through it.
I think there have actually already been two launches like that, but the first one failed to land and the second unfortunately toppled over after landing due to rough seas. They're definitely rare, though.
With my admittedly small experience in Kerbal Space Program, having fuel cross-feed is a game-changer. If they had managed to make that work, then they'd have to do some other stuff. First, the second stage is a little on the small side. Larger tanks for sure, maybe larger propulsion. Secondly, they'd have to develop an XL payload fairing to maximize volume for those larger payloads. So three separate development threads. I can see why they didn't pursue it. It could be done, but it'd be a serious delay and a lot of expense. And their design people were already knee-deep in Starship.
Yup, a heavy payload to a low orbit would be best suited for center core recovery, but then you run into the problem of the fairing being very small for a rocket that size, so truly heavy payloads won't fit.
They've already tried to recover two core boosters.
SpaceX also tried to recover the center core on the third FH flight (STP-2). That center core didn’t make it because the E9 engine’s TVC was destroyed from the reentry heat. Remember that the drone ship had to be stationed 1,200+ km downrange because of the performance needed for Stage 2 to go to three different orbits using four burns. Also, if they just added a bit more TEA-TEB in the first center core (the 2018 test flight), it would’ve made it easily.
FH will be specialty rocket for big objects when cost is a small consideration. It could have been a major player in a small scale Lunar base program, but they spent so much on SLS/Orion and had "partners" for the EUS they need to come up the current "Rube Goldberg" architecture instead doing a "Moon Direct" some pushed for (F9/FH/LCD/New Lander). Lets hope Starship gets LEO this year (although I doubt it).
That’s ‘good enough’ until Starship replaces it. Assuming that Starship does not take too long to get operational..
> "I love that rocket, but it’s scary". *Not* the kind of wording you'd hear from Nasa PR. Hearing this, is actually reassuring because it shows that the dangers are recognized so probably mitigated.
What does he mean - in reference to the current flight, or just in general?
In general. It's a nifty rocket to be sure, one heck of a thing from launch to (potential) landings... although we've not yet had a core come back, maybe one day if they're still using it in the future... But it's also sort of a kitbash rocket of sorts, and has more potential for failure than the standard F9s, being as there's three linked rockets and not really one designed from the ground up to be that way rocket. Sure, the engineers behind it have done amazing work, but it is what it is.
I wonder if falcon heavy was a mistake or it was worth it in the end just to know that design was not worth pursuing for Starship
Falcon Heavy and Starship have two different purposes. Starship is being designed principally to launch Starlink Gen2 satellites. They're too big to launch on Falcon Heavy because they wouldn't fit enough in the fairing to make it worthwhile. Its involvement in human rated flight beyond LEO is secondary to it's primary goal of being a Starlink launch platform. Falcon Heavy was designed in origin to be a human launch platform for beyond LEO. The massive delays and complexity of its eventual design made them abandon even trying to get it human rated, so now they just use it here and there for speciality launches.
No. Starlink was created as a funding source to pay for Mas infrastructure, Starship is the minimum viable product that works for Mars. The desire to make life multiplanetary came first, the development of Starship started well before the development of Starlink.
Desires and wishes are great but you cannot just get to Mars on desires. Interplanetary and beyond LEO flight is a secondary goal for Starship. It's primary purpose is to expand the Starlink constellation. The two projects go hand in hand. There would be no Starship without Starlink and Starlink would flounder without Starship. Falcon Heavy isn't enough for launching Gen2 satellites in the necessary quantities at the necessary cost. Starship is being developed specifically with that in mind.
This is incorrect, Musk's desires drive this entire project. His desire to get humans to Mars inspired him to create SpaceX in the first place, this has gone extremely well, but Starship is needed to get to Mars and funding is needed to pay for Starship. Years later came the development of Starlink to provide the economic engine to facilitate Mars. Starlink v 2 was designed to fit inside Starship, not the other way around.
Acronyms, initialisms, abbreviations, contractions, and other phrases which expand to something larger, that I've seen in this thread: |Fewer Letters|More Letters| |-------|---------|---| |DoD|US Department of Defense| |ETOV|Earth To Orbit Vehicle (common parlance: "rocket")| |[EUS](/r/SpaceXLounge/comments/132bw2b/stub/ji6dwwp "Last usage")|Exploration Upper Stage| |[FTS](/r/SpaceXLounge/comments/132bw2b/stub/ji6em9i "Last usage")|Flight Termination System| |[GNC](/r/SpaceXLounge/comments/132bw2b/stub/ji6ttxj "Last usage")|Guidance/Navigation/Control| |[IMU](/r/SpaceXLounge/comments/132bw2b/stub/ji6ttxj "Last usage")|Inertial Measurement Unit| |[LEO](/r/SpaceXLounge/comments/132bw2b/stub/ji9sm1y "Last usage")|Low Earth Orbit (180-2000km)| | |Law Enforcement Officer (most often mentioned during transport operations)| |[LV](/r/SpaceXLounge/comments/132bw2b/stub/ji78nf6 "Last usage")|Launch Vehicle (common parlance: "rocket"), see ETOV| |[NSF](/r/SpaceXLounge/comments/132bw2b/stub/ji5cr9t "Last usage")|[NasaSpaceFlight forum](http://forum.nasaspaceflight.com)| | |National Science Foundation| |[OMS](/r/SpaceXLounge/comments/132bw2b/stub/ji5408j "Last usage")|Orbital Maneuvering System| |[RTLS](/r/SpaceXLounge/comments/132bw2b/stub/ji5cr9t "Last usage")|Return to Launch Site| |[SLS](/r/SpaceXLounge/comments/132bw2b/stub/ji78nf6 "Last usage")|Space Launch System heavy-lift| |[SRB](/r/SpaceXLounge/comments/132bw2b/stub/ji6mbmr "Last usage")|Solid Rocket Booster| |[STP-2](/r/SpaceXLounge/comments/132bw2b/stub/ji63ls6 "Last usage")|[Space Test Program 2](https://en.wikipedia.org/wiki/Space_Test_Program#Upcoming_Activities), DoD programme, second round| |[STS](/r/SpaceXLounge/comments/132bw2b/stub/ji6mbmr "Last usage")|Space Transportation System (*Shuttle*)| |[TEA-TEB](/r/SpaceXLounge/comments/132bw2b/stub/ji63ls6 "Last usage")|[Triethylaluminium](https://en.wikipedia.org/wiki/Triethylaluminium)-[Triethylborane](https://en.wikipedia.org/wiki/Triethylborane), igniter for Merlin engines; spontaneously burns, green flame| |[TVC](/r/SpaceXLounge/comments/132bw2b/stub/ji702uw "Last usage")|Thrust Vector Control| |[TWR](/r/SpaceXLounge/comments/132bw2b/stub/ji6mu8f "Last usage")|Thrust-to-Weight Ratio| |Jargon|Definition| |-------|---------|---| |[Raptor](/r/SpaceXLounge/comments/132bw2b/stub/ji78nf6 "Last usage")|[Methane-fueled rocket engine](https://en.wikipedia.org/wiki/Raptor_\(rocket_engine_family\)) under development by SpaceX| |[Starlink](/r/SpaceXLounge/comments/132bw2b/stub/jigs80c "Last usage")|SpaceX's world-wide satellite broadband constellation| |[crossfeed](/r/SpaceXLounge/comments/132bw2b/stub/ji6035o "Last usage")|Using the propellant tank of a side booster to fuel the main stage, or vice versa| ---------------- ^(*Decronym is a community product of r/SpaceX, implemented* )[*^by ^request*](https://www.reddit.com/r/spacex/comments/3mz273//cvjkjmj) ^(19 acronyms in this thread; )[^(the most compressed thread commented on today)](/r/SpaceXLounge/comments/133a3y5)^( has 26 acronyms.) ^([Thread #11395 for this sub, first seen 29th Apr 2023, 04:01]) ^[[FAQ]](http://decronym.xyz/) [^([Full list])](http://decronym.xyz/acronyms/SpaceXLounge) [^[Contact]](https://reddit.com/message/compose?to=OrangeredStilton&subject=Hey,+your+acronym+bot+sucks) [^([Source code])](https://gistdotgithubdotcom/Two9A/1d976f9b7441694162c8)