Starship, how many decades did we loose?

[tater]

I'm personally not very worried about NTR failures, but I think it's a non-starter to the public at large.

[magnemoe]

14 minutes ago, Dragon01 said:

Except you need 1G for reuse, anyway, unless you're not doing propulsive landing. Things like helicopter catch are risky and very involved to set up. If it's going to be anything like an airplane, the least you can do is a single stage suborbital booster with a reusable spacecraft. 

Or an NTR. It has high Isp, and running on methane can allow you to actually save mass on tankage over LH2. An airbreather is the next best thing, but it pretty much requires hydrogen as fuel, with all the problems that entails. 

No need for nuclear spaceplanes, either, you could have a VTVL SSTO with methane. Ultimately, every chemical attempt at reuseability will have similar problems to Space Shuttle.

You need 1G of an almost empty stage falcon 9 second stage is +100 ton at separation including payload and fairing, 5 ton empty. 4 ton empty. 
Yes an helicopter catch is risky, you might loose the second stage who you also sell as disposable, with that sort of setup you calculate in losses. 
Note that this is mostly relevant for an fully reusable small sat launcher. Replacing one web and starlink birds. Upper stage dry mass will here be <1 ton. 

NTR don't work for an reusable vehicle who land because of neutron make everything they hit radioactive over time. 
Soviet union would not be crazy enough to try this. 

[magnemoe]

4 hours ago, Lisias said:

IMHO the problem is not the cost of development, but the potential savings themselves.

NASA budget is approved by the Congress, and congressmen get elected by bringing the pork home.

The very Space Shuttle Program was constrained by this: a lot of technical decisions were taken on political criteria - as the booster's width!

Once the program was running, savings would need to be achieved indirectly (as not painting anymore the external fuel tank, did only once on the first flight of Columbia) as trying to really optimize the vehicle would reduce the "pork going home". That would hinder NASA funding next year.

Pure research and development are easier to fund on a new Space Race - that commandment from Trump to lay feet on the Moon in 5 years would probably keep NASA somewhat shielded from Pork Politics, as anything hindering this program would face direct presidential backslash.

But then someone else would need to fulfil now mundane tasks, as provisioning the ISS. Again, relying on a foreign (and not necessarily friendly) nation to provide such critical role is terribly problematic on a strategic point of view, but also on a finantial one: the Pork is going overseas, no congressmen wants to be responsible to this!

I expect that at least some SpaceX decisions end up having to secure some Pork to someone - but  not to the point of undermine the profitability of the enterprise.

 

Booster width was constrained by maximum width on railroads. This is just an bit wider than the width of an M1 tank for the same reason. it also restrict the width of an falcon 9 even if not transported by rail the 3.5 meter width is maximum you can move on roads without serious and expensive preparations. 
The booster company probably also made ICBM who are not used much, who is nice, I do not want to live in an timeline there an clip loader for Ohio subs are an thing
On the other hand during WW2 feeding battleships at sea was SOP, other stuff you don't want to be standard operational procedure.  

Then again the B1 bomber had parts build in far more than 40 states. Its not an US thing either. In Norway, over an 30 year period it was an non aligned faction focusing on using road construction money on building tunnels and bridges in their provinces. You vote for me and I vote for you. And yes it took an generation to spot this. 
 

[magnemoe]

41 minutes ago, tater said:

It doesn't need to hover, it needs to reach low velocity at h=0.

Regardless, engines on upper stages need to push the full vehicle (mostly propellant), and only need to propulsively land a time % of that (dry mass plus any return payload. Something like Starship is 1300 tonnes wet, and with landing props, 100-something. Thrust is not really an issue.

Even TSTO with horizontal landing is better.

Take any SSTO spaceplane you envision. Lower the propellant tankage, and/or increase the payload. Put it on top of a similar, but much larger vehicle that accelerates it up to the speed where it would just about go full rocket and head to space. You now have a 100% reusable vehicle with better payload. It adds the complexity of staging, but eliminates the complexity of dual modes for the spacecraft, and allows the 2 stages to be optimized for their respective tasks.

TSTO horizontal landing would probably work well, might work better than starship if your focus is LEO only, and its second stage. 
You could just stall and tail land if no runway but this is an design decision or Micronesia 

[tater]

5 minutes ago, magnemoe said:

TSTO horizontal landing would probably work well, might work better than starship if your focus is LEO only, and its second stage. 
You could just stall and tail land if no runway but this is an design decision or Micronesia 

Yeah, many of the early VTHL shuttle design concepts had two stages that both landed horizontally. They had tiny wings, but the AF crossrange requirement ended up killing the small wing versions. It might be interesting to see a LEO cargo variant (tanker?) of SS that adds gear and glides in.

[Guest]

1 hour ago, magnemoe said:

NTR don't work for an reusable vehicle who land because of neutron make everything they hit radioactive over time. 
Soviet union would not be crazy enough to try this. 

Neutron activation can be worked around. For starters, you can give the thing a coating of boron-10, which will neatly take care of neutron radiation. Hydrogen isn't subject to activation, and IIRC methane isn't, either. That leaves you with reactor components, in which case it probably wouldn't be worse than in any naval reactor. NTR exhaust is typically not radioactive, and if you pick the pad materials right, the pad won't be activated, either.

NTRs only work for a reusable vehicle, because of the costs of building one. The only question is whether you reuse it on orbit or land it back on Earth. You don't want to throw away fully functional nuclear reactors.

Oh, and BTW, Soviet Union actively researched gas core nuclear rockets and were well on their way to building one when the engineers involved were reassigned to working on Zenit instead. So an NTR liftoff is really nothing they wouldn't consider, if they had the tech to implement it at the time.

1 hour ago, tater said:

I'm personally not very worried about NTR failures, but I think it's a non-starter to the public at large.

Russians don't seem too concerned, what with their airbreathing nuclear jet for cruise missiles. Yes, they do have a real, flight-proven nuclear jet engine. If their space industry was less neglected then they could probably try going into nuclear LVs. 

Edited May 17, 2019 by Guest

[sh1pman]

 

22 minutes ago, Dragon01 said:

Russians don't seem too concerned, what with their airbreathing nuclear jet for cruise missiles.

Those cruise missiles are supposed to be used as a last resort in situations where public opinion is irrelevant and radioactive pollution of targeted territory is desirable. Not what you’d want during a regular orbital launch.

...also, I don’t think this nuclear jet cruise missile is real, but that’s another story.

[Guest]

It's real enough to cause an incident during testing when it fell into the sea, reactor and all. Yes, they were testing them in arctic (somewhere around Kamchatka, IIRC) under nuclear power. Also, it's Russia. Public opinion is irrelevant anyway.  Helps with running projects like this, that's for sure.

Not that there is any cause for concern, as I said, NTR exhaust doesn't cause radioactive pollution. This isn't project Pluto. The reactor elements themselves can be shielded to prevent escape of radioactive material into the airstream (I sure hope they did shield the ones in Burevestnik, or at least in the test vehicles...). A RUD involving an NTR would be a cause for concern, but NERVA team did a destructive test and it proved their design safe in that situation. I'm sure any new NTR will only be better on that front, NERVA was a very primitive design. 

Edited May 17, 2019 by Guest

[mikegarrison]

All it takes is one bad COPV and your launch vehicle is scattered in bits downrange or exploded at your launch pad. I don't want it to be highly radioactive when that happens.

[tater]

1 hour ago, mikegarrison said:

All it takes is one bad COPV and your launch vehicle is scattered in bits downrange or exploded at your launch pad. I don't want it to be highly radioactive when that happens.

I know the NTR guys at Marshall have considered this, and their design is basically an RV that can survive any RUD, and be pulled off the ocean floor and reused (as an RTG once was). They've also switched to far less enriched fuels.

Doesn't entirely mitigate the threat---and certainly not for aircraft flying over land masses---but it's probably possible to not be terribly concerning. Regardless, however, I don;t see nuclear aircraft as a viable alternatove any time soon, and even if they were, TSTO versions would still be better.

[Lisias]

On 5/17/2019 at 6:54 PM, magnemoe said:

Booster width was constrained by maximum width on railroads. This is just an bit wider than the width of an M1 tank for the same reason. it also restrict the width of an falcon 9 even if not transported by rail the 3.5 meter width is maximum you can move on roads without serious and expensive preparations. 

That was an issue due the decision to build and refurbish the SRB on Utah.

Quote

By the early 1970's NASA researchers had already conducted a separate 10-year, $150 million program to develop very large booster rockets, and they considered only those with no segments, joints or troublesome O rings. Contrary to customary agency procedures, officials of that program were excluded from deliberations on the final choice of booster rockets for the space shuttle.

https://www.nytimes.com/1986/12/07/us/nasa-chief-might-not-take-part-in-decisions-on-booster-contracts.html

 

Edited May 20, 2019 by Lisias
Kraken carry the mobile autocomplete!

[DerekL1963]

On 5/17/2019 at 7:27 PM, Lisias said:

That was an issue due the decision to build and refurbish the SRB on Utah.

Every choice of SRB was fraught with problems.  Every single one.

Those big rockets?  Huge problems...  Starting with "nobody knew how to handle them".  They have to be cast nose down , handled level, and raised nosed up for assembly - and their size and weight posed serious challenges to handling and moving them w/o potentially damaging the grain.  They'd be a serious challenge even today.  They're heavy enough and large enough that they can't be practically transported any distance, so they'd have to be cast at KSC.  (Heck, they're large enough and heavy enough that even transporting them within the bounds of KSC posed a daunting problem.)  That's a significant safety problem.  Storing them would also be a significant safety problem due to the sheer mass of explosive in each booster. 

Speaking of casting the motors...  that's another (huge) known unknown.  The SRB's had to match (IIRC) within 5% - and the batch size was for a matched LH and RH segment pair was within the bounds of existing technology.  Nobody knew how to cast a pair of matched monolithic boosters.  Heck, they'd had problems casting even one during the testing down in South Florida.  (IIRC, the final test blew the nozzle off due to rough combustion attributed to casting problems.)

Etc... etc...

Big monolithic SRB's, contrary to the nonsense believed by many, were not a magic solution.  They would have required an expensive and extensive R&D program to a TRL where they could be considered ready for flight...  and even then, as outlined above, extensive problems remained to be tackled.

[Guest]

The problems with SRBs ultimately all come down to them being SRBs. One advantage of a solid rocket is that it's cheaper, and thus throwing it away is no big loss. Designing a rocket to be reusable increases its cost considerably, stripping away all advantages SRBs had. 

"Political interference" (that is, budget cuts) is what forced them to use SRBs in first place. All things considered, they went with the least bad option that they were given. Although adding thrust termination ports probably wouldn't have hurt, in retrospect...

[Vanamonde]

An argument about politics was turning personal and has been snipped from this thread. Keep it on-topic, please, and as always, leave politics out of things. 

[wumpus]

On 5/22/2019 at 6:37 PM, DerekL1963 said:

Every choice of SRB was fraught with problems.  Every single one.

Those big rockets?  Huge problems...  Starting with "nobody knew how to handle them".  They have to be cast nose down , handled level, and raised nosed up for assembly - and their size and weight posed serious challenges to handling and moving them w/o potentially damaging the grain.  They'd be a serious challenge even today.  They're heavy enough and large enough that they can't be practically transported any distance, so they'd have to be cast at KSC.  (Heck, they're large enough and heavy enough that even transporting them within the bounds of KSC posed a daunting problem.)  That's a significant safety problem.  Storing them would also be a significant safety problem due to the sheer mass of explosive in each booster. 

Speaking of casting the motors...  that's another (huge) known unknown.  The SRB's had to match (IIRC) within 5% - and the batch size was for a matched LH and RH segment pair was within the bounds of existing technology.  Nobody knew how to cast a pair of matched monolithic boosters.  Heck, they'd had problems casting even one during the testing down in South Florida.  (IIRC, the final test blew the nozzle off due to rough combustion attributed to casting problems.)

Etc... etc...

Big monolithic SRB's, contrary to the nonsense believed by many, were not a magic solution.  They would have required an expensive and extensive R&D program to a TRL where they could be considered ready for flight...  and even then, as outlined above, extensive problems remained to be tackled.

True, but many of those problem could be reduced by using 4 smaller SRBs (perhaps Aerojet200s?, where 200~=260*sin(pi/4)).  I'd expect that this was a valid course of action, and if the lunar rendezvous wasn't the plan they would probably have used something descended from the Aerojet260.  As long as the F-1 could get there (and I don't see a single Aerojet260 replacing it, although that might be a good plan for smaller cargo craft) and you needed the F-1, there was no reason to develop some other means of blowing up your rocket.

- Edit: Anybody know how they determined the size of the Aerojet260?  Did they want two boosters so they only had to worry about a single dimension for their gimbals?  I'd assume that four boosters would average out the errors more (and that X-rays could get a good idea of how much thrust each booster would produce.  You can X-ray them without ignition, right?).

"They would have required an expensive and extensive R&D program to a TRL where they could be considered ready for flight": pretty much the description of the entire Apollo program (although some of it was proven in Gemini, but the whole point of Gemini was to prove things for Apollo).

 

Edited May 25, 2019 by wumpus

[DerekL1963]

18 hours ago, wumpus said:

Did they want two boosters so they only had to worry about a single dimension for their gimbals?

I suspect that had more to do with limited attach points where the SRB thrust was symmetric and jettisoned SRB's wouldn't hit the Orbiter.
 

18 hours ago, wumpus said:

"They would have required an expensive and extensive R&D program to a TRL where they could be considered ready for flight": pretty much the description of the entire Apollo program (although some of it was proven in Gemini, but the whole point of Gemini was to prove things for Apollo).

Not quite, the Apollo Program managers avoided new tech absolutely as much as possible.  That is, they avoided research (as much as possible) and concentrated (where possible) on systems that only required development. It's a subtle, but important distinction.

Ditto Gemini.  Gemini was conceived after Apollo, and the design definition of the latter was largely complete and the design frozen two years before Gemini flew.  Gemini contributed a great deal in terms of flight experience, but very little in the way of hardware or specific technologies.
 

On 5/24/2019 at 3:00 AM, Dragon01 said:

Although adding thrust termination ports probably wouldn't have hurt, in retrospect...

 
They did examine thrust termination ports...  But the problem was the shocks and loads of sudden loss of thrust were sufficient to shred the ET, tossing the orbiter uncontrolled into the airstream.  (This is basically what happened to Challenger,  and she was destroyed by aerodynamic forces.)  It was proposed to add a solid rocket to the orbiter in order to provide the necessary control, but it was too heavy. 

[wumpus]

8 hours ago, DerekL1963 said:

Not quite, the Apollo Program managers avoided new tech absolutely as much as possible.  That is, they avoided research (as much as possible) and concentrated (where possible) on systems that only required development. It's a subtle, but important distinction.

Reminds me of the quote "I never, never want to be a pioneer" by none other than Seymour Cray (a man responsible for the fastest computers in the world from 1960s-1980s, often holding the title until his next computer eclipsed the old one).  Still, Apollo simply had to push a lot of tech in a lot of directions.  And developing things like the F-1 engine (which was far beyond a simple scale up of the old systems) might as well been a research project on its own (they blew up an amazing number of combustion chambers trying to find a means of combustion stability).

To be honest, I think the idea of massive monolithic SRBs died when Apollo decided they didn't need them.  Certainly there are some hefty boosters left with 1 minute burns, but nothing quite like the Aerojet260s.  One potential fit might be using something like the SR118 (Peacekeeper first stage) for a large rocket's auxiliary boosters (they burn for 56.6s).  Orbital/Northrop has considerable experience using them for the Minotaur rockets, so could potentially try something like that (I doubt that anyone else would be interested).

[magnemoe]

21 hours ago, wumpus said:

Reminds me of the quote "I never, never want to be a pioneer" by none other than Seymour Cray (a man responsible for the fastest computers in the world from 1960s-1980s, often holding the title until his next computer eclipsed the old one).  Still, Apollo simply had to push a lot of tech in a lot of directions.  And developing things like the F-1 engine (which was far beyond a simple scale up of the old systems) might as well been a research project on its own (they blew up an amazing number of combustion chambers trying to find a means of combustion stability).

To be honest, I think the idea of massive monolithic SRBs died when Apollo decided they didn't need them.  Certainly there are some hefty boosters left with 1 minute burns, but nothing quite like the Aerojet260s.  One potential fit might be using something like the SR118 (Peacekeeper first stage) for a large rocket's auxiliary boosters (they burn for 56.6s).  Orbital/Northrop has considerable experience using them for the Minotaur rockets, so could potentially try something like that (I doubt that anyone else would be interested).

They did a load of inventions. 
However they did not invent if brute force worked also cost was not much of an issue , time was the main constrain. 
They probably drew lots of their experience from WW2 there development faced the same issues, time was the ultimate currency. 
Granted during WW2 they had lots of fall back projects like the B36 bomber, yes it was pretty much on hold once they know it was not needed. 

[DerekL1963]

On 5/25/2019 at 5:39 PM, wumpus said:

Reminds me of the quote "I never, never want to be a pioneer" by none other than Seymour Cray (a man responsible for the fastest computers in the world from 1960s-1980s, often holding the title until his next computer eclipsed the old one).  Still, Apollo simply had to push a lot of tech in a lot of directions.  And developing things like the F-1 engine (which was far beyond a simple scale up of the old systems) might as well been a research project on its own (they blew up an amazing number of combustion chambers trying to find a means of combustion stability).

But that's the thing - the F1 was already in development before the Apollo project.  The CSM's design was well advanced (as a general purpose Earth orbiter) before Kennedy set us on the road to the Moon.  Sometimes I get this feeling that folks think that NASA managers sat down with a blank sheet and got started the morning after Kennedy's speech...  When nothing could be further from the truth.  The only part of Apollo that was anything resembling clean sheet was the LEM.  Much of the rest of the Apollo Project was largely cobbled together and adapted/developed from bits and pieces of programs and projects that were already in progress.  This wasn't an accident.
 

15 hours ago, magnemoe said:

They probably drew lots of their experience from WW2 there development faced the same issues, time was the ultimate currency. 

WWII and the Cold War...  When you read the biographies of a lot of middle and senior folks at NASA and with the contractors during Apollo, they're often a litany of ever larger and more complicated aerospace projects in the 1950's.  That's one of the unsung secrets of Apollo's success, the level of recent engineering and management experience with the rapid development and deployment of cutting edge aerospace systems.

[wumpus]

24 minutes ago, DerekL1963 said:

But that's the thing - the F1 was already in development before the Apollo project. 

Designing an F-1 before Apollo would have similar criticisms to SLS today: it was an engine to nowhere.  Obviously R&D groups have a place for such things, but there would never be the funding to fix its combustion instability (perhaps using the Soviet solution of more combustion chambers).

Perhaps a better example would be the Saturn 1 (aka "clusters last stand").  The thing had a first stage of 8 H-1 engines (apparently an on going design like the F-1) and fuel tanks from Redstone and Juno missiles.  The upper stage was another cluster of 6 RL-10s (replaced by a single J-2 in the Saturn IB).  All of these were clearly cobbled together from projects before the Kennedy speech, but the Saturn IB was still the primary means for putting men in orbit (when you don't need a heavy lift) until the Shuttle (used for Skylab and Apollo-Soyuz).

Still, the project employed something like 50,000 people over 10 years (I assume there was a ramp-up and ramp-down on the total), even a combination of trying to play "KSP with real parts*" and developing those parts into exactly what they needed took mind boggling amounts of labor.

24 minutes ago, DerekL1963 said:

WWII and the Cold War...  When you read the biographies of a lot of middle and senior folks at NASA and with the contractors during Apollo, they're often a litany of ever larger and more complicated aerospace projects in the 1950's.  That's one of the unsung secrets of Apollo's success, the level of recent engineering and management experience with the rapid development and deployment of cutting edge aerospace systems.

One thing the Smithsonian emphasises at the Enola Gay exhibit was that designing/building the B-29 that dropped the bomb (and had already flattened much of Japan) was a *bigger* project than the Manhattan Project itself.  I can only imagine what it took to build the B-52 (and civilian jets as well).

As an engineer, I'm fairly surprised that Elon Musk could try to use Silicon Valley style engineering and management for aerospace and auto development, but it appears to work.  I suspect that Paypal had to be significantly more secure than your typical web page or windows app, and he insists on a stronger engineering foundation than typical in San Jose.  In any event, it certainly understands "rapid development and deployment" in a way that aerospace (and particularly the military-industrial side of things that typically runs space projects in the USA) has largely forgotten.

* "KSP with real parts" appears to be Orbital/Northrup's main line of work.  Just look at how they've made rockets since Pegasus.

[DerekL1963]

On 5/27/2019 at 7:06 AM, wumpus said:

Designing an F-1 before Apollo would have similar criticisms to SLS today: it was an engine to nowhere. 

Not really, no.  The political environment of the 1950's-early 1960's was radically different from today.  Rockets were growing by leaps and bounds, and a huge engine with no current requirement seemed like a prudent investment in the future.  The F-1 wasn't the only such speculative project...  Just one of the few that eventually saw the light of day.  In some ways, the Apollo CSM itself (in it's earliest incarnations) can be seen as equally speculative...  A general purpose earth orbiter, when no clear requirement for such existed.  Later, a lunar lander when NASA had no significant funding for such a venture and only the vaguest intention of going to the Moon sometime in the future.   ("Possibly in time for the country's 200th birthday" according to some early documents.)

 

[IncongruousGoat]

On 5/27/2019 at 10:06 AM, wumpus said:

Perhaps a better example would be the Saturn 1 (aka "clusters last stand").  The thing had a first stage of 8 H-1 engines (apparently an on going design like the F-1) and fuel tanks from Redstone and Juno missiles.  The upper stage was another cluster of 6 RL-10s (replaced by a single J-2 in the Saturn IB).  All of these were clearly cobbled together from projects before the Kennedy speech, but the Saturn IB was still the primary means for putting men in orbit (when you don't need a heavy lift) until the Shuttle (used for Skylab and Apollo-Soyuz).

Still, the project employed something like 50,000 people over 10 years (I assume there was a ramp-up and ramp-down on the total), even a combination of trying to play "KSP with real parts*" and developing those parts into exactly what they needed took mind boggling amounts of labor.

Well, the Saturn I is kind of an odd one, and the history of how it came about has nearly nothing to do with Apollo. The proposal that would eventually lead to the Saturn I was called the Saturn A-1. It was developed (along with the rest of the Saturn family) by von Braun's team at ABMA (later, NASA Huntsville), and had that Jupiter/Redstone cluster as a first stage, the first stage of a Titan I as the second stage, and Centaur as the third stage. It was proposed in 1959 as the fastest way for the U.S. to get heavy-lift capability in excess of that of the USSR, and at first it was greenlit exactly as written. Then, things started getting complicated. The Air Force got involved in the whole thing, partially because of the need on ABMA's part to negotiate with them regarding contracts and supply for Titan I first stages, and partly because these early LV programs were organizational tangles. From the Air Force's involvement came a demand for a 160-inch hydrogen-fueled second stage (as opposed to the 120-inch kerosene-fueled Titan stage then planned), which would be needed for Saturn to be able to launch Dynasoar. After some political twists and turns, including a largely fanciful proposal for a Titan-derived heavy lift vehicle from the Air Force, the Saturn program was eventually switched over to that 160-inch hydrogen stage, for use with Dynasoar. The second production lot of Saturn Is was even configured to launch Dynasoar... which was switched to launching on the Titan 3C, and then cancelled. Saturn I, of course, only flew a handful of times before being replaced by the (Apollo-derived) Saturn IB.

The worst part is that I just covered a part of the history after 1959. The earlier stuff is even wackier, especially some of the configuations that were considered for that first stage. Chestnuts like an R-7-ish purely parallel-staged booster, or a first stage with the liquid kerosene tank wrapped around the LOX tank.

There's some more reading on the subject here: http://astronautix.com/s/saturni.html

Edited May 29, 2019 by IncongruousGoat