A Test-flight Launchpad for SH/SS

[Ionmars]

Face-palm.

I have been wondering, as many others have, why we are not seeing any construction activity and no plans for building a suitable launch pad for SS/SH. The time is fast approaching when SpaceX needs to test and launch a full stack Starship/Super-heavy booster, but we THINK we see no effort to build the necessary giant launchpad, GSE, and flame trench. Such a launch facility would normally require a five-year project, but where is it?

It finally occurred to me that they already have almost everything they need right in front of us at 39A. In fact, they have too much equipment! The answer is that Boca Chica is the initial testbed not only for building a Starship, but also for transporting it to a launch facility and launching it. The one facility lacking at BC to launch the full stack is the flame trench, so they will transfer the whole launch procedure to Florida and use the existing trench for further testing!

What facility is required to build the whole stack? A 4-acre open field somewhere near the launchpad.

How do they transport SH and SS from construction site  to 39A? Separately, on multi-wheeled beds that operate on normal roads. Always vertical.

How do they place SH onto the launch trench? By a large mobile crane parked next to 39A. No ramp required.

How do they stack SS onto SH? By the same large mobile crane parked next to 39A.

How do they load LOX into SS and SH? Through the bottom of SH, which also has a feed line up into SS. The existing LOX tanks could be used by building a branch line to serve the pad from a different angle. Optionally, they could bring in additional LOX tanks as is done at BC.

How do they load LCH4 into SH/SS? Same as LOX, using additional tanks brought in.

How do they light the stack and control the flight? I don’t know, but same as BC.

What about the Fixed Service Structure already at 39A? Don’t need it for SH/SS test flights.

Any questions? Don’t ask me, I’m just an observer. 

[Keldor]

Appearances are misleading.

My understanding is that most of the time spent in building a launchpad has to do with getting the earth beneath it to settle in order to create a solid foundation.  This involves things like piling a big mound of dirt on the site and leaving it to sit for a few years while its weight slowly compresses and drives the water out of the earth below to make a nice solid foundation.  But they've already done this at Boca Chica!

Once the ground is finally prepared for the foundation, the rest of the construction can go quite fast.  A flame trench is just a big trench in the ground with concrete sides.  The service tower is a heavy duty scaffolding with pipes running up it.  Tanks, trenches for pipes, lightning rods, launch clamps...  None of this is likely to take very long to install once the ground is ready to support it.

The foundation is everything.  It has to support thousands of tons of fueled up rocket, and then nothing shortly afterward.  This sort of dynamic load flexes and cracks and is in general much harder on the foundation than a building which just peacefully sits there.  And all this is on top of land that started out as marshy unstable coastland.

[Ionmars]

Appearances are misleading.

My understanding is that most of the time spent in building a launchpad has to do with getting the earth beneath it to settle in order to create a solid foundation.  This involves things like piling a big mound of dirt on the site and leaving it to sit for a few years while its weight slowly compresses and drives the water out of the earth below to make a nice solid foundation.  But they've already done this at Boca Chica!

Once the ground is finally prepared for the foundation, the rest of the construction can go quite fast.  A flame trench is just a big trench in the ground with concrete sides.  The service tower is a heavy duty scaffolding with pipes running up it.  Tanks, trenches for pipes, lightning rods, launch clamps...  None of this is likely to take very long to install once the ground is ready to support it.

The foundation is everything.  It has to support thousands of tons of fueled up rocket, and then nothing shortly afterward.  This sort of dynamic load flexes and cracks and is in general much harder on the foundation than a building which just peacefully sits there.  And all this is on top of land that started out as marshy unstable coastland.

I think you are right. At 39A the ground is settled and the trench is already built. It did require special cladding to withstand the high temperature and force of 13 million pounds thrust.

SpaceX says they applied for permits to launch from both BC and Florida. ISTM they could save money by using the existing trench, if they are allowed.

[IainMcClatchie]

The foundation is everything.  It has to support thousands of tons of fueled up rocket, and then nothing shortly afterward.  This sort of dynamic load flexes and cracks and is in general much harder on the foundation than a building which just peacefully sits there.

I'm curious how SeaLaunch handled this dynamic load during/after launch.  It looks like they used a semisubmersible with a minimal waterline.  The small waterline means that big waves don't kick the platform around much.  But it also means that large changes in load, requiring large changes in displacement, will cause the platform to lurch vertically in the water.

I'm also curious about how a jack-up platform deals with dynamic loads.  It has some sort of foundation: whatever the interface is between those vertical trusses and the sea floor.  Is it typical to just hammer piles into the sea floor and let the friction between the piles and the clay handle the dynamic loads?  Piledrivers don't work overnight but they don't take months either, and it does seem that you could decouple from underwater pads to tow the barge into dock, and then recouple to those same underwater pads later.

Decoupling/recoupling to an underwater LOX and LNG pipeline seems more risky, but it also seems you could have a permanent abovewater terminal for those, to which a jack-up rig and barge for carrying the SS could dock.

[Ionmars]

The foundation is everything.  It has to support thousands of tons of fueled up rocket, and then nothing shortly afterward.  This sort of dynamic load flexes and cracks and is in general much harder on the foundation than a building which just peacefully sits there.

I'm curious how SeaLaunch handled this dynamic load during/after launch.  It looks like they used a semisubmersible with a minimal waterline.  The small waterline means that big waves don't kick the platform around much.  But it also means that large changes in load, requiring large changes in displacement, will cause the platform to lurch vertically in the water.


I'm also curious about how a jack-up platform deals with dynamic loads.  It has some sort of foundation: whatever the interface is between those vertical trusses and the sea floor.  Is it typical to just hammer piles into the sea floor and let the friction between the piles and the clay handle the dynamic loads?  Piledrivers don't work overnight but they don't take months either, and it does seem that you could decouple from underwater pads to tow the barge into dock, and then recouple to those same underwater pads later.

Decoupling/recoupling to an underwater LOX and LNG pipeline seems more risky, but it also seems you could have a permanent abovewater terminal for those, to which a jack-up rig and barge for carrying the SS could dock.

I also looked into an ocean launch platform for SH/SS. I thought It was the only way SpaceX could build out a launch facility to meet their self-imposed schedule. I started a thread by that name to discuss it.

That’s why I began this thread with “face palm,” an expression of embarrassment that an obvious and  less expensive solution was readily available.

[Ludus]

A major reason for assuming that they needed a new pad was the assumption they wanted to implement the full rapid reuse system including landing SH on the launch mount. That wouldn’t be accepted at 39a, and any mods to require it would interfere with the F9/FH use of 39a.

If they put legs on SH and land both it and SS at the regular LZ that’s not a problem.

Doing it this way means giving up the ambition for very rapid reuse at first but I’m sure that’s secondary to getting it flying ASAP.

Working on both sites gives them an alternative if they hit obstacles.

[abc2010x]

So does this mean they could still launch the orbital prototype in 2020, or would the time needed to build the launch pad stop this? I know that there are other factors could also delay them beyond 2020.

[su27k]

It finally occurred to me that they already have almost everything they need right in front of us at 39A. In fact, they have too much equipment! The answer is that Boca Chica is the initial testbed not only for building a Starship, but also for transporting it to a launch facility and launching it. The one facility lacking at BC to launch the full stack is the flame trench, so they will transfer the whole launch procedure to Florida and use the existing trench for further testing!

So you're assuming they'll only build and fly Starship prototype at Boca Chica, and SuperHeavy will be built and launched at Florida?

This assumption doesn't seem to fit Elon's tweet about "Working on regulatory approval for both Boca Chica, Texas, and Cape Kennedy, Florida. Will also be building Starship & Super Heavy simultaneously in both locations."

I think regulatory approval is one of the reasons there's no construction activity, they won't start constructing a launch pad for SuperHeavy at a location until they get approval for launching SuperHeavy from that location.

[geza]

It is clear that the Hopper will be launched from the concrete pad at Boca Chica, a la Grashopper.

As the orbital prototype is under construction at Boca Chica also, it is generally assumed that it will be launched from the same pad, without a flame trench. This is surprising, because the SS is supposed to have around 1000 ton fueled mass, more than 3x heavier than a Soyuz rocket. Well, SS is supposed to be launched without a flame trench from Mars, also. However, as somebody explained in one of the many discussions here, there is no acoustic problem in the thin air of Mars.

However, nobody assume launching the SH without a flame trench. You may be right with LC39A. Without an offshore pad, SH have to be launched from there, first for hops, then for flights with SS on the top.

However, LC39A needs more than some additional pipes and tanks. it needs the structure that holds, and holds down, the entire stack, heavier than a fueled Saturn V. For the Saturn/Shuttle/Falcon launches this structure was/is located on a mobile launcher.  So the question is whether it is possible to equip the launch pad with a permanent, fixed hold down structure for SH without interfering with the F9/FH launches? The hold down structure for the Falcon transporter/erector at LC39A is reconfigured between F9 and FH launches. Something similar for the FH fixed hold down?

The fixed service tower of LC 39A is used now, as crew access arm. It will be useful later in the same role for SS. The crew escape system is in place. I can imagine, that LC39A will remain the location for crewed (maybe, cargo) launches while an offshore pad will do the more frequent, and more routine tanker launches.

 

[Ionmars]

A major reason for assuming that they needed a new pad was the assumption they wanted to implement the full rapid reuse system including landing SH on the launch mount. That wouldn’t be accepted at 39a, and any mods to require it would interfere with the F9/FH use of 39a.

If they put legs on SH and land both it and SS at the regular LZ that’s not a problem.

Doing it this way means giving up the ambition for very rapid reuse at first but I’m sure that’s secondary to getting it flying ASAP.

Working on both sites gives them an alternative if they hit obstacles.

ISTM they don’t have to give up any long term goals, such as landing on the launch mount. To meet short-term goals, however,  they are using landing legs like F9. If they pass on the landing mount, it would probably be for a technology reason.

[Ionmars]

To meet short-term schedule, a lot rides on the launch permits and whether a flame trench will be required. Alternative scenarios:

1. They receive permits for both BC and 39A in short order. ISTM they would go for 39A first to avoid the cost of building a trench and to accelerate the schedule.

2. They receive a permit for BC quickly, but 39A is delayed. ISTM they would grit their teeth and build a trench at BC first. Optionally, they could use an ocean platform if they had already started the work in secret. Second option, they could build an elevated launch framework rather than a trench and employ a mobile metal flame deflector under SH.

3. They receive a permit for 39A quickly, but BC is delayed. In this unlikely event, ISTM they would definitely go to 39A first.

4. (Added) Permits for both BC and 39A are delayed. Then the ocean launch platform may be the best route to meeting schedule. But it wouldn’t be cheap.

[speedevil]

It is clear that the Hopper will be launched from the concrete pad at Boca Chica, a la Grashopper.

As the orbital prototype is under construction at Boca Chica also, it is generally assumed that it will be launched from the same pad, without a flame trench. This is surprising, because the SS is supposed to have around 1000 ton fueled mass, more than 3x heavier than a Soyuz rocket. Well, SS is supposed to be launched without a flame trench from Mars, also. However, as somebody explained in one of the many discussions here, there is no acoustic problem in the thin air of Mars.

Very, very stupid fixes may also work.
A 10cm thick plate, and an 8m 5cm tub around the bottom of the stage around the engine bells is 'only' some 90 tons.

[Keldor]

I don't see any particular reason they couldn't start restricting F9/FH to LC-40.  They'd have to expand or replace their service tower for crewed flights, but that's not really a show stopper.  I don't think even NASA could find a reason to drag their feet over the safety of a simple tower with an elevater and an access arm.  I mean, they do have that zip line system on LC-39B, and the associated bunker, but an escape method like this on a rocket with fueling once the astronauts are inside and the ground crew evacuated and an launch escape system having any sort of practical use is pretty far fetched.

They can keep the clamps and tooling for F9 and FH nearby and ready in case LC-40 gets fragged.  Reinstalling them to convert LC-39B back to use with the Falcon rockets should be finished sooner than the fleet is ungrounded.

Since LC-39B is so historic, SpaceX wants to use it for their most prestigeous flights.  Right now that means FH and crew Dragon.  But SH/SS will overshadow that.

Eventually they will want redundancy in case something gets blown up.  They might also want more rapid launch cadence with Starlink and all.  This means a Boca Chica pad in likely to happen in the future.

If permitting drags on to the point where SpaceX has a rocket ready and it's causing delays, I wouldn't be the least bit surprised to see an executive order come down the pipe to get their butts in gear.  Permitting and associated regulations are done by the Executive branch, and the launch facilities are overseen or outright run by the feds, again Executive branch.  The president would be completely within his rights here.  Even with Boca Chica, federal law overrides state law, and the feds are the authority for launches.

[Ionmars]

I don't see any particular reason they couldn't start restricting F9/FH to LC-40.  They'd have to expand or replace their service tower for crewed flights, but that's not really a show stopper.  I don't think even NASA could find a reason to drag their feet over the safety of a simple tower with an elevater and an access arm.  I mean, they do have that zip line system on LC-39B, and the associated bunker, but an escape method like this on a rocket with fueling once the astronauts are inside and the ground crew evacuated and an launch escape system having any sort of practical use is pretty far fetched.

They can keep the clamps and tooling for F9 and FH nearby and ready in case LC-40 gets fragged.  Reinstalling them to convert LC-39B back to use with the Falcon rockets should be finished sooner than the fleet is ungrounded.

Since LC-39B is so historic, SpaceX wants to use it for their most prestigeous flights.  Right now that means FH and crew Dragon.  But SH/SS will overshadow that.

Eventually they will want redundancy in case something gets blown up.  They might also want more rapid launch cadence with Starlink and all.  This means a Boca Chica pad in likely to happen in the future.

If permitting drags on to the point where SpaceX has a rocket ready and it's causing delays, I wouldn't be the least bit surprised to see an executive order come down the pipe to get their butts in gear.  Permitting and associated regulations are done by the Executive branch, and the launch facilities are overseen or outright run by the feds, again Executive branch.  The president would be completely within his rights here.  Even with Boca Chica, federal law overrides state law, and the feds are the authority for launches.

If the full stack SH/SS is ready for testing by the end of this year, where do you think they will launch it? Will they have their permits by then?

[jstrotha0975]

I really think 39A makes the logical choice not only for initial full stack tests, but in the long term as well. For short term Starship and Superheavy can be assembled in a field near by and transported to near the pad the same way they transported the hopper and lift it by a giant crane. SH with legs first (will need minimal infrastructure, mainly CH4 supply) and the SS behind it and stacked on top. After tests are complete (by that time I believe SpaceX will have built a second fully equipped launch pad elsewhere) and F9 crew and FH are no longer needed, you upgrade the infrastructure at 39A with a new tower and landing cradle hanger and ramp.

[geza]

The minimal SH infrastructure for LC39A is a mobile launch pad, which is compatible externally with the launch pad part of the Falcon transporter-erector. Before a launch, either a the transporter goes out with the Falcon, or the SH launch pad. In the latter case a mobile crane will lift the SH to the launch pad.

[ThomasGadd]

The first couple of launches of SH will have fewer engines so the pad requirements are less. 

Boca Chica offers fewer scheduling issues than KSC.  Fear of fraging LC-39A is there as well. 

LC-39A is Spacex, LC-39B is SLS and LC-39C is unused. 

This year (2019) they are building two hoppers (the next one will be orbital), next year (2020) they are building the first SS/SH. 

Where they launch the full power stack is an interesting question and a different thread...

[envy887]

It is clear that the Hopper will be launched from the concrete pad at Boca Chica, a la Grashopper.

As the orbital prototype is under construction at Boca Chica also, it is generally assumed that it will be launched from the same pad, without a flame trench. This is surprising, because the SS is supposed to have around 1000 ton fueled mass, more than 3x heavier than a Soyuz rocket. Well, SS is supposed to be launched without a flame trench from Mars, also. However, as somebody explained in one of the many discussions here, there is no acoustic problem in the thin air of Mars.

The pad at Boca Chica does have rainbirds for sound suppression.

[enbandi]

LC-39A is Spacex, LC-39B is SLS and LC-39C is unused. 

I am afraid that LC-39C is not existing actually. As I know there had been a plan for a third Saturn class launch pad in tbe row, but only A and B have been built, and C had been cancelled. Check google maps, there are only two of the same kind.

There can be some confusion since there was a renumbering also (what we know as A was originally the C i think) and there is a small sat launcher stan next to the B whic reffered as C.

[ThomasGadd]

There is a good WIkipedia article on it:

https://en.wikipedia.org/wiki/Kennedy_Space_Center_Launch_Complex_39