For Questions That Don't Merit Their Own Thread

[WinkAllKerb'']

please define OCD over mathemical restricted syntaxes languages over metaphorical languages without syntaxe & lexical restriction *in / out*

Edited June 11, 2019 by WinkAllKerb''
& lexical

[ZooNamedGames]

NASA had plans to make their hypersonic and suborbital X-15 spaceplane into an orbital version before straight up upgrading to the X-20 Dyna-soar. Their plans was to use the Navajo missile to launch the X-15. 

My question is-  how was the Navajo missile planned to compensate for the offset center of mass center of mass since it was proposed to be side launched Space Shuttle style? Or did they just draw that concept up and put no effort into making sure it would work?

[wumpus]

1 hour ago, ZooNamedGames said:

NASA had plans to make their hypersonic and suborbital X-15 spaceplane into an orbital version before straight up upgrading to the X-20 Dyna-soar. Their plans was to use the Navajo missile to launch the X-15. 

My question is-  how was the Navajo missile planned to compensate for the offset center of mass center of mass since it was proposed to be side launched Space Shuttle style? Or did they just draw that concept up and put no effort into making sure it would work?

I doubt they got far enough to worry about such things.  I'm also continually amazed at how early some tech appears: there was a team seriously trying to put the first man in space with ramjets as a significant source of delta-v!

If you don't know what "isn't possible" with your infrastructure, there's often no reason not to try it.  Pretty much every "fancy" tech in cars (except maybe some stuff that absolutely requires computers) was available in the 1920s.  Mass producing long-lasting parts would often take till late in the 20th to early 21st tech. 

[kerbiloid]

They were going to use not Navajo itself, but a quad of Navajo's boosters (or even their engines).
http://www.astronautix.com/x/x-15b.html

Spoiler

The white one.

So, probably just something like here, but with the quad instead of the single first stage.

Spoiler

 

 

Edited June 12, 2019 by kerbiloid

[wumpus]

9 hours ago, kerbiloid said:

They were going to use not Navajo itself, but a quad of Navajo's boosters (or even their engines).
http://www.astronautix.com/x/x-15b.html

So, probably just something like here, but with the quad instead of the single first stage.

 

As much as I love the idea, two huge issues almost certainly killed it.

1.  Do you really think it is easier to provide 7000m/s to an X-15 than 9400m/s to a Mercury capsule?  They aren't light, and don't really have the delta-v (only 2400m/s) you'd expect from an upper stage.

2.  Re-entry heat.  A X-15 goes to heroic efforts to survive the heat from extreme speed, but it isn't designed for 9000m/s.  All returning spacecraft that I'm aware of keep the compressed heat away from the spacecraft to minimize heat.  A X-15 simply attempts to survive the heat, which is unlikely to work at de-orbiting speeds (it technically did re-enter from space).  It is also low-drag, so it will have to survive those temperatures for much longer and will certainly vaporize.

[ZooNamedGames]

1 hour ago, wumpus said:

As much as I love the idea, two huge issues almost certainly killed it.

1.  Do you really think it is easier to provide 7000m/s to an X-15 than 9400m/s to a Mercury capsule?  They aren't light, and don't really have the delta-v (only 2400m/s) you'd expect from an upper stage.

2.  Re-entry heat.  A X-15 goes to heroic efforts to survive the heat from extreme speed, but it isn't designed for 9000m/s.  All returning spacecraft that I'm aware of keep the compressed heat away from the spacecraft to minimize heat.  A X-15 simply attempts to survive the heat, which is unlikely to work at de-orbiting speeds (it technically did re-enter from space).  It is also low-drag, so it will have to survive those temperatures for much longer and will certainly vaporize.

Which is not doubt why they envisioned the X-20 to replace it when going to orbit.

[kerbiloid]

1 hour ago, wumpus said:

Do you really think it is easier to provide 7000m/s to an X-15 than 9400m/s to a Mercury capsule? 

It was a USAF & NASA project, they had a lot of the dismissed Navajo's boosters for free, and the military aviators of the world were considering spaceplanes as the space mainstream, while capsules as something unknown, less useful, and not reliable.
(Later this resulted into the Dyna Soar and Spiral projects.)

They were right, from a certain point of view.

They didn't need a long-term orbital ship, they needed a 1-2 turns around the Earth ready-to-launch recon/bomber/interceptor ship able to land on an appropriate airbase rather than in ocean or desert.

***

An airbase.
A launchpad with installed long-term storable launch vehicle and spaceship (like Titan+DynaSoar or Proton+Spiral). It's on duty for months.
Next to it a pilot on duty is sitting and reading journals.

There is a target to be processed, highly likely with unknown position. Maybe an aircraft carrier next to Hawaii, maybe a submarine in the Indian Ocean, maybe tank troops in Europe.
Nobody knows until the last minute what and where will it be.
The required heading is absolutely random, given at the last minutes.

Alarm. The pilot quickly gets into the ship.
The personnel quickly calculates the orbit inclination and flight plan to make the recon spaceship pass next to the target.
Launch.

***

Say, the target is an aircraft carrier moving somewhere there, at 30 kn speed in random directions.

Recon.
The recon spaceship is passing above its district, at very low orbit (150-200 km), just by several minutes after the launch.
The pilot sees the ship order, defines the aircraft carrier position with a mini-telescope, tells its current coordinates to the command center.
They launch either a missile or a bomber space ship.
The recon ship stays in orbit for one turn more. Its orbit inclination is random, not those "51°" or "37°" like normally.

***

Bomber..
The bomber space ship (from the same or another airbase) starts with 1-2 bombs with retroengines into a low orbit (say, 80-100 km).
It is not even an orbital flight, it's a circumnavigational one.
Its inclination is also random.
According to the target coordinates reconned by the recon, the bomber is heading to the target and drops the bombs.

The bombs fall as close to the target as they can.
The bomber reenters the atmosphere from his 80..100 km high periapsis, aerobrakes and...

... and founds himself in 1000 km from the nearest appropriate airbase, crossing its runway direction at 140° angle.
Because unlike the regular spaceships it enters the atmosphere at random direction and at random place.

So, the bomber has to perform a side maneuver up to 2000 km and change its flight direction on his wish.
Otherwise it will land in a desert, while the rescue teams are busy in other places. The ship will be lost, the pilot will have a long journey to the base.

***
Meanwhile the recon finishes one turn around the Earth, and passes above the target region for the second time.
It watches the results of bombardment with a telescope, makes photos, and reports to the command center that the target is destroyed.

They tell him to perform one more turn and watch another target on his way, then land.
He does this, deorbits with engine and...

... and faces the same problem like the bomber. Random place far from base, random flight direction.

***

Meanwhile they notice an enemy alternative partner's 1500-km-high satellite looking like a bad one.

They launch an inspector-interceptor ship with its pilot on duty.
They launch it in the custom direction, to make the interceptor ship pass next to the badsat in its first orbit turn (because the next orbit turn will pass in a thousand kilometers from the target).
I.e. in custom azimuth, too. Into a high single-turn orbit with random inclination.

The interceptor approaches to the badsat, the pilot looks at it through the telescope, makes photos, ensures that this sat is bad, and shoots it down with a cannon or missiles.

Then it deorbits and reenters...

... yes, it's at random place, too.

***

So, you now have three spaceships aerobraking at random places in random directions, and all what you can say about their landing zones, they will land somewhere on your territory, at +/- 2000 km from the closest airbase.

How to land them on an airbase? The only way: aerial maneuvering, i.e. a plane flight.
If they are capsules, it's bad to be them.
If they are planes, they just keep gliding, helping themselves with kerosene jets.

***

So, a spaceplane is the only way to return a combat spaceship to a base. So, the air forces (the most interested lobbyists) were wanting a spaceplane.
Irl they got just a capsule, and it can't be as flexible as a plane. Epic fail.

1 hour ago, wumpus said:

Re-entry heat.  A X-15 goes to heroic efforts to survive the heat from extreme speed, but it isn't designed for 9000m/s.  All returning spacecraft that I'm aware of keep the compressed heat away from the spacecraft to minimize heat.  A X-15 simply attempts to survive the heat, which is unlikely to work at de-orbiting speeds (it technically did re-enter from space).  It is also low-drag, so it will have to survive those temperatures for much longer and will certainly vaporize.

That's why they didn't get a spaceplane.

Edited June 12, 2019 by kerbiloid

[DDE]

On 6/11/2019 at 6:21 PM, kerbiloid said:

Tineye found similar pic here

Also they say that

Pat Rawlings' drawings about the Mars.

“Unmanned”, even though you can clearly see Apollo quads and an androgynous collar?

[DDE]

7 hours ago, wumpus said:

Re-entry heat.  A X-15 goes to heroic efforts to survive the heat from extreme speed, but it isn't designed for 9000m/s.  All returning spacecraft that I'm aware of keep the compressed heat away from the spacecraft to minimize heat.  A X-15 simply attempts to survive the heat, which is unlikely to work at de-orbiting speeds (it technically did re-enter from space).  It is also low-drag, so it will have to survive those temperatures for much longer and will certainly vaporize.

Quote

Like the original X-15B proposal, the next iteration of the craft would have had the same shape as the plain X-15. The biggest difference between the two planes was the materials used to make them. While the X-15 could get by with aluminum and steel for its frame, the X-15B’s orbital re-entry would have caused it to deal with much higher temperatures: as high as 2700 Celsius on the leading wing edges. Regular structural metals would sag and melt when subjected to that.

As a result the nickel alloy Inconel X, which was used only for the heat-resistant skin of the X-15, was restricted to the area of the plane’s frame behind the nose and above the belly. Those other two areas, as well as the wings and tail fins, had to use more exotic refractory materials like graphite, molybdenum, and beryllium oxide. Where the heat was worst, NAA planned on using thorium(IV) oxide, which means that—like its predecessor the Douglas Model 684—the X-15B would have been somewhat radioactive. Unlike the Douglas plane only structural elements for the tail fin edges and the roots of the wing edges would have used the stuff, not the whole skin.

The skin of the plane would have been even more exotic, including molybdenum, tungsten, the René-41 alloy used for the shell of the Mercury capsule, and niobium. The last of these was a particularly interesting call as at the time the Dyna-Soar was also looking as if it were going to made out of the same metal, and together they would have used up more than the world’s annual production of the metal for a few years.

https://falsesteps.wordpress.com/2012/09/15/x-15b-shortcut-to-space/

[wumpus]

23 hours ago, ZooNamedGames said:

Which is not doubt why they envisioned the X-20 to replace it when going to orbit.

Looks like the X-20 uses a similar strategy as the Shuttle in returning from orbit.  I wonder if they would have had similar (or worse) issues with tile replacement on the X-20.

23 hours ago, kerbiloid said:

It was a USAF & NASA project, they had a lot of the dismissed Navajo's boosters for free, and the military aviators of the world were considering spaceplanes as the space mainstream, while capsules as something unknown, less useful, and not reliable.
(Later this resulted into the Dyna Soar and Spiral projects.)

They were right, from a certain point of view.

A point of view that insisted that the glory of the air force officer corps trumped such unimportant issues such as mass when going into orbit for example...

Van Braun showed that missiles were an effective (if overexpensive means for delivery of conventional ordinance.  Although sending bombers straight into the RAF to attack London instead of attacking the RAF directly was probably even worse) means of delivering bombs.  It just didn't get Air Force pilots those required combat missions to advance.  Recon made a lot more sense for manned missions: the means to return film from space might have impressed Rube Goldberg (at least until electronic cameras and storage caught up).  Doesn't look like they would have any advantages of looking through less atmosphere.  Combat: see bombing run, and even less reason to drag around all of that non-weapon mass.

The X-20 program simply was a preview of the Shuttle issues, where the "spaceplanes are cool" vision won over boring issues of mass.  Seeing how it was started in 1957 (when Sputnik launched) it was hard to believe it managed to continue through 1961 (Shepard's suborbital launch) and 1962 (John Glenn's orbital flight), although it is possible that it was hard to kill space programs during the spacerace.  Oddly enough, the Saturn 1 had lifted off in 1961, paving the way to lift such heavy contraptions and might have saved the thing.  But it must have been disheartening watching the string of failures to respond to Sputnik all the while knowing you had to build a far more massive booster to heave this heavy load into orbit.

For those interested in the Dyno-Soar: it is Amy Teitel's favorite spacecraft and a number of videos should be on "Vintage Space": https://www.youtube.com/channel/UCw95T_TgbGHhTml4xZ9yIqg

[ZooNamedGames]

9 minutes ago, wumpus said:

Looks like the X-20 uses a similar strategy as the Shuttle in returning from orbit.  I wonder if they would have had similar (or worse) issues with tile replacement on the X-20.

Likely hard to say- the tiles initially were used as a way to ensure reusability for the Shuttle. If the Dyna-soar wanted to sacrifice some reusable parts for reentry, they could've created ablative tiles. Or even coated the airframe in ablative coating- which, as a reminder, worked on the X-15 test flight. The main issue with the coating during the X-15 flight was with the X-15 and not the coating. It ablated as intended, the issue was the airframe of the X-15 was designed to cool through the airframe and it's skin, which the coating prevented. Assuming they built the X-20 with this knowledge in mind they could've engineered the vehicle to survive that issue. The X-20 was also slightly smaller than the X-15 so coating would've not been a problem, minus the time spent recoating it after every mission.

[kerbiloid]

1 hour ago, wumpus said:

Van Braun showed that missiles were an effective

if your target is London-sized, motionless, 300 km far, and you don't care about particular targets because anyway can't aim.
Even with spotting ~1.5 km error (at 300 km distance).

V-2 carried < 1 t of ammo and was made mostly of the cheap iron (with aluminium inner tanks) and fueled with cheap alcohol and oxygen.
Absolutely fine when you launch them right from the backyard of an underground plant, but unlikely a really significant weapon right at the moment.

***

American army was interested in tools for her tasks, so more short-range rockets. ICBM was not matching their daily needs. So, they inherited it but weren't interested in ICBM or space too much.
Navy tried V-2 but again they needed something maching their typical distances, so ICBM was not in order, too.

USAF already had thousands of long-range heavy bombers (unlike USSR) and ICBM was an interesting-but-not-necessary thing, while an extension of aircraft abilities was greatly appreciated.
So, they were the most interested lobbyists of anything space-related, but not because of space, but because of getting better planes, spaceplanes.
Capsules-schmapsules were nerdish toys for them, never really tested and looking unreliable compared to the well-known planes, having no room for bomb bays or any reusable equipment..
While a spaceplane would be just a better plane.

And intercontinental winged missiles like Navajo and Snark. For USAF this was familiar and matching their daily needs. An uncrewed long-range bomber, i.e a plane, too.

NACA was not NASA until the oops! with R-7 and Sputnik, so they were not deciding what to choose.

***

As USSR and Germany were mostly continental states, they needed first of all tactical aviation, not flying fortresses.
They tried several, but as the resources were limited, so they had to build only tactical bombers and fighters.
While USA and UK were hiding behind the big water pools and mostly building long-range bombers and sea fighters.

After WWII USAF was mostly continuing what they always did with planes, trying also tactical missiles. While USSR was forcing both bomber and ICBM.
As a result the first ICBM (poor but existing) appeared at the Soviet side, making Americans to force their ICBMing and make von Braun a rocket boss.

***

And as we can see, the first Soviet projects implemented in metal were intercontinental winged missiles, too: Buran and Burya (Blizzard and Storm), 1950s.
Because they were more accurate, predictable, reliable, and already tested than those fancy ballistic rockets.

As we can see, before the Vostok project, the Soviet constructors were developing a ten of spaceplane projects in 1950s.
Because the airforce operates with planes, not with capsules.

***

Both capsules (Vostok and Mercury) were a big step... back to the dull reality from the spaceplane tactics.

Edited June 13, 2019 by kerbiloid

[wumpus]

9 hours ago, kerbiloid said:

if your target is London-sized, motionless, 300 km far, and you don't care about particular targets because anyway can't aim.
Even with spotting ~1.5 km error (at 300 km distance).

How does the saying go?  Horseshoes, hand grenades, and nuclear weapons?  Sputnik certainly showed that the R7 could be maintained within a few degrees of target all the way around the world (this might not hit Washington DC, but the place might as well be surrounded by "consolation targets").

The real problem was that aside from recon, there was no particular reason to send up a spaceplane.  And only the spaceplane was likely reusable, so the costs would be vastly higher than using an ICBM or a capsule.  A spaceplane is like a flying car: it is trying to cover two worlds that aren't similar enough for one design to cover both.

The Air Force certainly wanted a spaceplane.  They had plans for a spaceplane.  But the laws of physics, mainly the rocket equation (and thermodynamics for the X-15 (not that the X-20 wouldn't have reentry issues)) made it next to impossible to build an effective spaceplane.  Once Sputnik and Yuri Gurgarin made it clear that the US needed to get in space *now*, this impossible dream needed to be sidelined (but kept popping up in Shuttle and Dream Chaser).

It is almost like a faction in NASA/USAF have this steampunk-like fantasy, only instead of Victorian-era they want the sci-fi of the 1950s (with spaceplanes, not Elon Musk's tail-lander 1950's throwback).  It doesn't matter how badly this fits the situation, they just demand that style.

Edit: there also seems to be a faction demanding SSTO.  How you can make funding decisions at NASA without understanding the rocket equation I'm not sure (except after hearing second hand how such things are handled, I'm no longer surprised), but far too many things get budgets for this stupid fantasy.

Edited June 14, 2019 by wumpus
noted edit

[ARS]

Does a spacecraft DeltaV change vector is affected by the direction of the nozzle or the direction of gas that's expelled from that nozzle? I mean, if we outfit the spacecraft engine nozzle with target-type thrust reverser, the moment the thrust reverser deflector doors deployed, the thrust reversal (theoretically) takes effect and the doors block the expelled gas in the end of the engine. In this case the gas passes through the inner surface and travels frontward to provide force opposite to the heading of the spacecraft. Assuming the spacecraft is on stable orbit, should the craft:

A. DeltaV increases (velocity change in respect of gas expelled from nozzle)

B. DeltaV decreases (velocity change in respect of gas deflected frontward)

C. No change (velocity change of nozzle gas is counteracted by deflected gas)

Assume the reverser able to reverse 100% of gas from the nozzle, which one is going to happen?

[kerbiloid]

 

3 hours ago, wumpus said:

How does the saying go?  Horseshoes, hand grenades, and nuclear weapons?

?
Original accuracy/error of V-2 was ~10 km. Later they added a radio command system, the error was decreased to 1.5 km.
At just 300 km range (not 10 000 km intercontinental), with a rocket made-of/fueled-with the cheapest scrap never used later in real rockets.
So, V-2 had demonstrated ability to hit something with a rocket in short range, but absolutely not its advantage over long-range bombers and winged rockets.
Because 10000 / 300*1.5 = 50 km. You can't even be sure which state you hit with it.

Further von Braun's descendants of A4/V-2 were winged (i.e. uncrewed rocketplane missiles):
Gleiter A4, Flossengeschoss A-4, A8 (a winged hypergolic descendant of A4/V-2 ) were to have 400..550 km range.
The wingeed Flossengeschoss A4 was considered as the second stage for ICBM based on A-10 as first stage.

A4 V12/a,b,c projects had different types of wings.
The A4 V12/c with 6-meter wings became A9, the second stage for A9/A10. Distance (project) 750 km.

(And so on, they were working on a whole bunch of winged A4 descendants).

The first von Braun's official rocketship project was a winged VSHL A9 with a pilot cabin and attached ramjet, not a capsule. Range 1800 km, up to 3000.

Von Braun himself is demonstrating what is a spaceship in 1940s.

Spoiler

 

Based on his A9/A10/A11 project (with winged A9 as uncrewed orbital stage/cargo ship. 1 t of payload) and further A9/A10/A11/A12 multistage rocket with launch mass 3500 t.

Any capsule of him?

 

3 hours ago, wumpus said:

Sputnik certainly showed that the R7 could be maintained

Years later, in 1957.

Eugen Saenger's circumnavigational bomber Silbervogel - 1939-late 1940s (tests of scaled prototypes and equipment). His later projects - till 1960s.
Von Braun's winged rocketships (tests of scaled prototypes and equipment) - 1940s.

1946-47. USAF still were not sure what do they want: a ballistic or a cruise intercontinental missile.
So, they purchased several projects at once: winged MX-770,771,775 and ballistic (who knows, what if it flies) -774.
Winged Matador, Snark - 1947, Navajo - 1956.

Intercontinental ICWM accuracy in late 1940s was ~ 1km. While late 1950s ICBM ~10 km (later ~5 km).

In 1956 the range of Navajo with 3 t  of payload was 9 600 km. While Atlas could deliver just about a ton.
So, only a minitiaruzation of thermonukes allowed ICBM have a chance, when the warheads got 1 t heavy, so no huge winged missiles were required anymore to deliver it.

A sudden stop of X-15 project after 1961, being continued by numerous lifting-body crafts and later Space Shuttle.

1952-1963 - DynaSoar and its ancestors.

USSR:
1947 - Silbervogel clone project, HSHL (launch from railway), hybrid propulsion, intercontinental. Engines development, deep investigations.
1948 - Two-stage winged airborne ramjet missiles.
1953 - Two-stage ICWM EKR with winged ramjet 2nd stage, 8000 km. Korolev's bureau, equipment development and testing
1954-60 - Buran and Burya two-stage ICWM, implmeneted in metal, flight tests, actual range 6 500 km. In 1960 the general constructor Lavochkin died, the project closed.
1956-1960 Miasishchev's "satelloids" i.e. rocketplanes. Theoretical studies.
1958 - Tsybin's rocketplane to be launched by R-7. Theoretical studies.
1958 - Tupolev's spaceplane projects.
1960 - Chelomei's family of rocketplanes unified with maneuvering warheads. Practical tests of warhead prototypes

 

3 hours ago, wumpus said:

The real problem was that aside from recon, there was no particular reason to send up a spaceplane.

There was no particular reason to send a capsule.
Because the spaceplanes were being designed on purpose, not "to send". They should be performing practical tasks typical for aviation but in significantly extended range.
Nobody needed a spaceship just to fly into space.

Capsules were being studied by Korolev (just because a rocket), by Chelomei and Miasishchev (as junior members of corresponding spaceplane families) and never were a thing until the ICBM flights when every side decided "we have a rocket, let's launch at least something to shock'em all".

So, when spaceplane development faced problems, both sides launched simple capsule with limited abilities, and stopped developing spaceplanes having at the moment unclear perspectives.

Capsules were not "what they need" but just "what they could".

MOL and Almaz were quicklaunch-recon-on-duty systems with capsules, but they were whole orbital stations and couldn't be mass-launched due to their cost.
While recon spaceplanes should be quickly reusable, so were limited only by the launch vehicles cost.
While capsules were able just to deliver crew to the stations.

So, the capsule spaceships were not a win but a defeat from the practical usability point of view.

 

3 hours ago, wumpus said:

A spaceplane is like a flying car: it is trying to cover two worlds that aren't similar enough for one design to cover both.

A spaceplane is the way to save mass using stored orbital kinetic energy for atmospheric flight. More effective than an additional rocket stage.
A capsule is just a lifeboat.

Just civil needs do not at the moment require spaceplanes because they use a limited set of inclinations, and just service an orbital station, and have a crew of <6.
So,  the capsules are and always were just a temporary solution between the "space combat aviation" and "space civil aviation" epochs.

 

3 hours ago, wumpus said:

But the laws of physics, mainly the rocket equation (and thermodynamics for the X-15 (not that the X-20 wouldn't have reentry issues)) made it next to impossible to build an effective spaceplane

The laws of physics don't make it impossible.
Just in 1950s the task looked easier, and in early 1960 they got a "quick-and-dirty" solution (capsules) and postponed the space aviation till better times.

3 hours ago, wumpus said:

Once Sputnik and Yuri Gurgarin made it clear that the US needed to get in space *now*

Not actually "needed" but "simply must" for the reputation.
As well as lunar program. Noone really needed the quasi-suicidal projects of 1960s except for PR race, with puny landers attached to tiny capsules. With obviously no continuation.
The Moon was not in order in any sense.
If there were no PR race, the first lunar expeditions would happen (wait... OH, ..) now, after several LEO space station and a LOP-G as a base.

3 hours ago, wumpus said:

It is almost like a faction in NASA/USAF have this steampunk-like fantasy

Sci-fi fantasies were exactly the capsules, pure "lemme-send-da-man-in-da-space cuz it's kool !" of the rocketeers.

While the spaceplane were an absolutely practical vision of the space utilization, instead of "exploration" and "colonization" (of the vacuum, lol!).
Just they were technically too hard at that moment, nothing more.

Originally the spaceplanes were required for tactical needs, later they will be required for passenger flights.
Capsules are just a placeholder in between.

Edited June 14, 2019 by kerbiloid

[IncongruousGoat]

I was reading through the stuff that's going to launch on STP-2 and noticed among the manifest GPIM, or the Green Propellant Infusion Mission. For those who don't know, GPIM is a mission intended to test HAN (hydroxylammonium nitrate), a "green" monopropellant that's expected to get around 250s Isp (compared to straight hydrazine's ~200s).

Does anyone here know the history of this stuff? It isn't mentioned by name in Ignition!, though it seems to be related to a collection of monopropellants investigated by Clark's team that all consisted of the nitrate salt of an amine, dissolved in WFNA. Clark does offhandedly mention running across some liquid salts while making the nitrate salt of every amine he could get his hands on, and presumably HAN is one of those, but it seems like Clark gave up on those when he couldn't get them to crystallize & dissolve in the acid. Interest must have picked up again at some point, but my Google-fu is failing me as to when and under whom that happened. I have found this DOE report: https://www.osti.gov/servlets/purl/1374990 from 1998, but it's just a summary of what HAN is used for. It does mention a plutonium reclamation plant using the stuff starting in 1964, so knowledge about it is nothing new, and it seems odd that monopropellant research would have passed it over until very recently.

[DDE]

On 6/14/2019 at 5:59 AM, wumpus said:

It is almost like a faction in NASA/USAF have this steampunk-like fantasy, only instead of Victorian-era they want the sci-fi of the 1950s (with spaceplanes, not Elon Musk's tail-lander 1950's throwback).  It doesn't matter how badly this fits the situation, they just demand that style.

Edit: there also seems to be a faction demanding SSTO.

It’s based on major presuppositions about how the high-frequency launch vehicles should operate: no restacking, no fetching different stages from different locations, and if at all possible the spacecraft should be launched, retrieved and processed using the existent airport infrastructure. Professionals study logistics, hurr-durr.

[magnemoe]

On 6/12/2019 at 5:31 PM, kerbiloid said:

It was a USAF & NASA project, they had a lot of the dismissed Navajo's boosters for free, and the military aviators of the world were considering spaceplanes as the space mainstream, while capsules as something unknown, less useful, and not reliable.
(Later this resulted into the Dyna Soar and Spiral projects.)

They were right, from a certain point of view.

They didn't need a long-term orbital ship, they needed a 1-2 turns around the Earth ready-to-launch recon/bomber/interceptor ship able to land on an appropriate airbase rather than in ocean or desert.

***

An airbase.
A launchpad with installed long-term storable launch vehicle and spaceship (like Titan+DynaSoar or Proton+Spiral). It's on duty for months.
Next to it a pilot on duty is sitting and reading journals.

There is a target to be processed, highly likely with unknown position. Maybe an aircraft carrier next to Hawaii, maybe a submarine in the Indian Ocean, maybe tank troops in Europe.
Nobody knows until the last minute what and where will it be.
The required heading is absolutely random, given at the last minutes.

Alarm. The pilot quickly gets into the ship.
The personnel quickly calculates the orbit inclination and flight plan to make the recon spaceship pass next to the target.
Launch.

***

Say, the target is an aircraft carrier moving somewhere there, at 30 kn speed in random directions.

Recon.
The recon spaceship is passing above its district, at very low orbit (150-200 km), just by several minutes after the launch.
The pilot sees the ship order, defines the aircraft carrier position with a mini-telescope, tells its current coordinates to the command center.
They launch either a missile or a bomber space ship.
The recon ship stays in orbit for one turn more. Its orbit inclination is random, not those "51°" or "37°" like normally.

 ***

Bomber..
The bomber space ship (from the same or another airbase) starts with 1-2 bombs with retroengines into a low orbit (say, 80-100 km).
It is not even an orbital flight, it's a circumnavigational one.
Its inclination is also random.
According to the target coordinates reconned by the recon, the bomber is heading to the target and drops the bombs.

The bombs fall as close to the target as they can.
The bomber reenters the atmosphere from his 80..100 km high periapsis, aerobrakes and...

... and founds himself in 1000 km from the nearest appropriate airbase, crossing its runway direction at 140° angle.
Because unlike the regular spaceships it enters the atmosphere at random direction and at random place.

So, the bomber has to perform a side maneuver up to 2000 km and change its flight direction on his wish.
Otherwise it will land in a desert, while the rescue teams are busy in other places. The ship will be lost, the pilot will have a long journey to the base.

***
Meanwhile the recon finishes one turn around the Earth, and passes above the target region for the second time.
It watches the results of bombardment with a telescope, makes photos, and reports to the command center that the target is destroyed.

They tell him to perform one more turn and watch another target on his way, then land.
He does this, deorbits with engine and...

... and faces the same problem like the bomber. Random place far from base, random flight direction.

***

Meanwhile they notice an enemy alternative partner's 1500-km-high satellite looking like a bad one.

They launch an inspector-interceptor ship with its pilot on duty.
They launch it in the custom direction, to make the interceptor ship pass next to the badsat in its first orbit turn (because the next orbit turn will pass in a thousand kilometers from the target).
I.e. in custom azimuth, too. Into a high single-turn orbit with random inclination.

The interceptor approaches to the badsat, the pilot looks at it through the telescope, makes photos, ensures that this sat is bad, and shoots it down with a cannon or missiles.

Then it deorbits and reenters...

... yes, it's at random place, too.

***

So, you now have three spaceships aerobraking at random places in random directions, and all what you can say about their landing zones, they will land somewhere on your territory, at +/- 2000 km from the closest airbase.

How to land them on an airbase? The only way: aerial maneuvering, i.e. a plane flight.
If they are capsules, it's bad to be them.
If they are planes, they just keep gliding, helping themselves with kerosene jets.

***

So, a spaceplane is the only way to return a combat spaceship to a base. So, the air forces (the most interested lobbyists) were wanting a spaceplane.
Irl they got just a capsule, and it can't be as flexible as a plane. Epic fail.

That's why they didn't get a spaceplane.

Very interesting and yes it makes perfect sense to focus on spaceplanes. 
They was simply fast planes who is correct. 
Wings as range extenders are not uncommon on bombs like the SDB
https://en.wikipedia.org/wiki/GBU-39_Small_Diameter_Bomb#/media/File:Boeing_GBU-39_Small_Diameter_Bomb.jpg
Even used on artillery shells. 

However it had some downsides, outside of reentry who would be solvable however with an mass or reusablity penalty. 
And major issue is weight, you are in practice putting an miniature space shuttle into low earth orbit, obviously doable but something who require an heavy orbital rocket to do. 

An ICBM would obviously be smaller. 
Same for asat an ground controlled satellite or missile is lighter.
Leaving recon and lots of the early manned flights was into recon capabilities but then more probably more on an longer term imaging space station.
Just launching an short lived satelite who dropped an film container was far more light weight if you wanted an fast image as it could be launched by an smaller rocket. 

In short they under estimated the size and complexity of the launch system, as you could not reuse the booster and likely not the space plane itself the only benefit was man on site. 
And yes this is an very undervalued feature especially today but cost here would be very high. 

On the other hand, they might get the last laugh. Its lots of focus on hypersonic weapons now as ballistic like ICBM can be intercepted by high end SAM/ASAT systems. 
If you come in slower but fly you are far harder to intercept as you can use the air to move around.
Something like starsip would be an nice bomber, Musk has even talked about wings on it .

On the gripping hand: 

 

[kerbiloid]

28 minutes ago, magnemoe said:

However it had some downsides, outside of reentry who would be solvable however with an mass or reusablity penalty. 
And major issue is weight

Yes and no. The wings are like an transformers of kinetic energy.
In orbit a ship has 8 km/s of kinetic energy stored from the rocket fuel. Like a flywheel.
When a capsule aerobrakes, all this energy dissipates as a heat waste and brings nothing except problems.

When a lifting body or a spaceplane reenters, the wings partially transform this kinetic energy into lifting force, allowing the ship to have a longer trip, improving its maneuverability and precision, and allowing less accurate deorbit. Also if a spaceplane has reentered above an ocean, it can keep flying and reach the coast. If weather is bad at the planned runway, it can change its route in flight.
So, the wings are like an additional stage. A rocket stage for that would be much heavier.

40 minutes ago, magnemoe said:

An ICBM would obviously be smaller. 
Same for asat an ground controlled satellite or missile is lighter.

Yes, so the spaceplanes were frozen.

42 minutes ago, magnemoe said:

Leaving recon and lots of the early manned flights was into recon capabilities but then more probably more on an longer term imaging space station.
Just launching an short lived satelite who dropped an film container was far more light weight if you wanted an fast image as it could be launched by an smaller rocket. 

The orbital stations can't pass across a custom region far from their orbit plane, while a recon-on-duty can be launched in any direction and reach the area of interest in minutes.

The problems with short--livings photosats were that only iirc ~30% of photos pictured something except clouds, and couldn't report the targets until landing and photo processing.
While a crewed spaceship with recon equipment contain its own data processor - the crew brains. So, they can analyze what are they seeing, and just report to the ground center: "The target identified and confirmed. Position coordinates: ... ..."
Also in case of Almaz (which is not a plane but could be used as a fast recon) it had a huge radar seeing through the clouds. So, if put something similar in a spaceplane, it could see through the targets, too

When the electronics got harder, and data transmission rate had dramatically increased, uncrewed sats occupied this ecological niche.

55 minutes ago, magnemoe said:

could not reuse the booster and likely not the space plane itself

Spiral and Dyna Soar were reusable. And Proton launch complex was highly automated to allow launches one by one.
So, if there is enough rockets in storehouse, they could try.

57 minutes ago, magnemoe said:

On the other hand, they might get the last laugh. Its lots of focus on hypersonic weapons now as ballistic like ICBM can be intercepted by high end SAM/ASAT systems. 
If you come in slower but fly you are far harder to intercept as you can use the air to move around.

Or if suppress radio communication, breaking any fast data transmission, and making uncrewed sats useless.

Then a small crewed spaceplane of 1950s can pass above the target and report its status  and coordinates in a short Morse message. Maybe even with a flashlight or with a laser reflector. covering it with a cap and opening

[Guest]

Let's say I want an electric motor to drive a high-rpm disk.

Is it better to use a high-rpm motor with somewhat lower torque, of to use a high-torque motor with a <1 gear ratio

[magnemoe]

1 hour ago, Aperture Science said:

Let's say I want an electric motor to drive a high-rpm disk.

Is it better to use a high-rpm motor with somewhat lower torque, of to use a high-torque motor with a <1 gear ratio

You want to avoid gearing if possible so high rpm. 
Think you pretty much never gear up electric motors. 

[Flibble]

Pretty easy to find motors up to 100,000 rpm, so why complicate things?

[kerbiloid]

There were: dark-gray Mercury, black Gemini, white Gemini, metallic Apollo, army-green Soyuz, white-gray Soyuz, gray Soyuz, army-green TKS, emerald-green Almas/Salyut, white-and-maroon zebra Salyut, white/black Shuttle, black Dyna Soar, can't understand-which-color Skylab, and so on.

Same ships in various colors.

Does the surface color actually affect something at all?!
White and black variants of Gemini make me doubt.

[Spacescifi]

 

Yes it does.

Darker colors absorb more heat. Which can be a problem on long interplanetary flights.

You will not see charcoal black colored spacecraft flying interplanetary missions anytime soon.

Lighter colors reflect more light and are more susceptible to radiation pressure. Radiation pressure is accounted for on long interstellar flights where craft coast for long periods.

If it radiation pressure was not accounted for, spacecraft would be pushed off course quite a bit.

On 6/19/2019 at 10:17 AM, kerbiloid said:

There were: dark-gray Mercury, black Gemini, white Gemini, metallic Apollo, army-green Soyuz, white-gray Soyuz, gray Soyuz, army-green TKS, emerald-green Almas/Salyut, white-and-maroon zebra Salyut, white/black Shuttle, black Dyna Soar, can't understand-which-color Skylab, and so on.

Same ships in various colors.

Does the surface color actually affect something at all?!
White and black variants of Gemini make me doubt.

So in short, it may matter little, unless it is a long interplanetary mission and the ship has to coast a lot.

Edited June 20, 2019 by Spacescifi

[kerbiloid]

6 hours ago, Spacescifi said:

So in short, it may matter little, unless it is a long interplanetary mission and the ship has to coast a lot.

And there were green Almaz/Salyuts, white-maroon zebra Salyut, white Mir modules, green TKS attached to Salyut as module and flying standalone, too.
All of them spent in orbit more or less compatible time (1+ years), And they definitiely had the same mass and construction, as they are clones of the same prototype.

Gemini were 10 times lighter, and they were designed for several weeks long mission (so, the same order of magnitude of received energy to mass ratio).

As a zero-G interplanetary mission unlikely can last longer than 2..3 years, so the only difference is that the interplanetary ship flies farther from Sun than a near-Earth ship, and receives a little less light.