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#251 2008-02-23 09:43:48

Terraformer
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From: Ceres
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Re: Earth to LEO - discuss

Well, technically a double afterburner. I don't know what an Acid/Alkali rockets thrust would be though. It should be possible to work it out from the thrust of a vineger/baking soda rocket, and some simple equations for how the explosive power increases as the PH gap goes up.


"I'm gonna die surrounded by the biggest idiots in the galaxy." - If this forum was a Mars Colony

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#252 2008-02-23 16:34:31

Terraformer
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Re: Earth to LEO - discuss

Hello, anyone except jumpboy11j going to comment on the idea?


"I'm gonna die surrounded by the biggest idiots in the galaxy." - If this forum was a Mars Colony

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#253 2008-02-23 16:45:54

GCNRevenger
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Re: Earth to LEO - discuss

Austin Stanley is correct, acid-base reactions look pretty impressive in their ability to generate heat sitting on the table in a lab, but are really quite poor per-gram compared to traditional rocket fuels. They would never make good fuels, especially with their corrosive nature.

And again, almost exclusively Hydrogen is consumed and combined with other chemicals in acid-base reactions and not rendered as H2.

They also tend to create solid ionic byproducts at relatively low temperatures (a bit above the boiling point of water), and since these don't expand like gasses, it would be difficult to make them contribute to the thrust very well. It would also serve to clog the engine too I would imagine, leading to catastrophic failure (boom). They will also be relatively heavy, and reduce Isp still further.

And finally, if you get energy out from burning Hydrogen and (shiver) Fluorine (deadly stuff), then it will take a lot of energy to break it back apart again. This is actually one reason why HF is a rather weak acid!


"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw

The glass is at 50% of capacity

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#254 2008-02-23 16:53:29

Terraformer
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Re: Earth to LEO - discuss

Seems the net has lied to me again. It told me Hydrofluric acid was more reactive than Hydrofluric, and would cause really bad damage if I got some on myself. I assumed it would react with a base like calcium to form Calcium Fluride and Hydrogen. I'll see whether I can do some tests in the schools tiny, ill-equipped science classroom.  lol  big_smile  smile  big_smile  lol  8)  8)

I'm sure Austin Stanley's post didn't turn up before now.


"I'm gonna die surrounded by the biggest idiots in the galaxy." - If this forum was a Mars Colony

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#255 2008-02-23 18:54:24

GCNRevenger
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Re: Earth to LEO - discuss

HF is especially nasty to people because it doesn't readily release its hydrogen atom; because the molecule is so small and remains uncharged since it keeps its Hydrogen, it simply slips deep into the tissue and through the cell walls in your cells. There, it does slowly split into H+ and F-, and this F- binds Calcium ions as CaF2 and causes cell death. The H+ stays in solution and is not evolved as H2 either. Hydrochloric acid, unlike Hydrofluoric, readily gives up its H+ ion, and as charged H+ & Cl-, which doesn't penetrate cell walls very well.

And on a personal note, you had better not play with Hydrofluoric acid, it is quite dangerous stuff due to the above. I am a professional chemist and I have to work with the stuff from time to time, stay away from it and always wear eye protection and vinyl, neoprene/chloroprene, or nitrile gloves. Most acids will just burn the heck out of your skin and yield superfical damage, but the usual treatment for severe HF exposure is amputation.


"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw

The glass is at 50% of capacity

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#256 2008-02-23 20:44:14

Austin Stanley
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From: Texarkana, TX
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Re: Earth to LEO - discuss

Seems the net has lied to me again. It told me Hydrofluric acid was more reactive than Hydrofluric, and would cause really bad damage if I got some on myself. I assumed it would react with a base like calcium to form Calcium Fluride and Hydrogen. I'll see whether I can do some tests in the schools tiny, ill-equipped science classroom.  lol  big_smile  smile  big_smile  lol  8)  8)

Hydrofluoric acid is simple Hydrogen Fluoride in an aqueous (water) solution.   Hopefully no chemistry teacher in his/her right mind will allow a highschool student to play around with HF.  Heck, hopefully most highschool chem labs don't even stock the stuff!  As GCRN HF is a particularly nasty substance in acid or (god help you) pure form.

However measuring the enthalpy of a acid-base reaction is really simple test that can easily be done in a high-school lab (heck you could do it in your kitchen if you had the right stuff).  A decent calorimeter can be made out of a couple nested Styrofoam cups.  And a good high school lab should have HCl, in both strong and probably already diluted to easy to handle concentrations.  Likewise it should be well stocked with a strong base (likely NaOH, lye), but you can easily get your hands on one of these if you like.  It really is a simple experiment, you can find a ready made procedure for it probably in a good chem 101 (possibly even high-school) text book/lab book, or on the net if that fails.  A great learning opportunity any teacher would jump on!


He who refuses to do arithmetic is doomed to talk nonsense.

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#257 2008-02-23 22:13:16

GCNRevenger
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Re: Earth to LEO - discuss

It really is a simple experiment, you can find a ready made procedure for it probably in a good chem 101 (possibly even high-school) text book/lab book, or on the net if that fails. A great learning opportunity any teacher would jump on!

Certainly, if you wear proper protection (safety glasses, non-latex gloves) and ventilation if you use high-strength acids. Having water close by is a good idea too (sink).

Liquid HF is reaaaally evil stuff, much worse than regular aqueous, neither of which anyone should be playing with!

PS: If you don't know what liquid vs aqueous means, you really really shouldn't be handling either.


"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw

The glass is at 50% of capacity

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#258 2008-02-24 07:01:59

Terraformer
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Re: Earth to LEO - discuss

Is it obvious? I'd assume aquaus means it's in water, whereas liquid is distilled stuff that's not in water?

Points taken, I was just using HF as an example.


"I'm gonna die surrounded by the biggest idiots in the galaxy." - If this forum was a Mars Colony

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#259 2022-09-14 06:04:37

Mars_B4_Moon
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Re: Earth to LEO - discuss

Concepts like Space Elevators seem like Scifi for now

Although this article claims, 'built within a decade'

Sci-Fi Space Elevators and Orbital Rings Will be Built with-in a Decade
https://markets.buffalonews.com/buffnew … n-a-decade

There is Pegasus, the mothership Stargazer there was an Orbital Space Plane Program https://web.archive.org/web/20061210225 … saacrv.htm Rocketplane XP, Dream Chaser, SpaceShipTwo, or the idea for Skylon  a combined-cycle air-breathing rocket propulsion system.

"Space Access: SKYLON – Technical".

https://web.archive.org/web/20151217042 … _tech.html

https://web.archive.org/web/20160820132 … kylon.html

The Chinese are testing Spaceplanes and making Private Companies

It could be argued reusable concepts existed before Shuttle and Buran, the Von Braun Ferry Rocket or General Dynamics Nexus, different times and even in the 90s Russia was once considered a partner for Space launch for tourism flights to the ISS, a place someone could buy from, however it is isolated with sanctions after the War in Ukraine, Russia calls ageing space station "dangerous" as it plans successor its own Russian Station, war and politics is against them it seems Russians won't be doing much in the future. Reusable launch vehicle has made space cheaper,  first reusable Space Plane launch vehicles were manufactured, named the STS Space Shuttle and Buran Energia. The big change since the thread was first posted is Elon Musk's ability to make space cheaper and more frequent access to reusable Heavy rockets.

NASA's SLS hydrogen leak is a sign of the Artemis program's outdated technology
https://interestingengineering.com/inno … technology

Inside NASA’s Struggle to Launch America Back to the Moon
https://www.yahoo.com/video/inside-nasa … 09318.html

Last edited by Mars_B4_Moon (2022-09-14 06:18:39)

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#260 2022-09-14 11:37:04

GW Johnson
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Re: Earth to LEO - discuss

The SABRE engine might work yet,  and has not been cancelled to the best of my knowledge.  Although it has languished for lack of funds a lot.  It's a liquid air cycle engine,  which by extremely-fast liquifaction using cryogenic hydrogen,  is how you do not exceed the air temperature limits that all types of turbomachinery otherwise have.

The Skylon vehicle was cancelled long ago. 

There were fatal problems with that design,  the most egregious of which is its inability to survive entry,  because of shock impingement heating. The shocks shed by the engine inlet spikes would impinge upon the adjacent wing leading edges,  and essentially cut the wings off in a matter of seconds.   Which is why no entry spacecraft has ever had parallel nacelles,  and none ever will.

Not so egregious,  but just as fatal,  is the lack of a published heat protection solution for nosetips and leading edges in any of the descriptions I have ever found for how that airframe was to be built.  That violates my prime rule for hypersonic vehicle designs:  "if you don't have a heat protection solution,  you don't have a design". 

What might work for lateral skins will NOT work for nosetips and leading edges.  We already know that.

I keep seeing Skylon crop up as a "good design we ought to try",  and I keep reminding people it would never have worked because of those fatal flaws.

GW


GW Johnson
McGregor,  Texas

"There is nothing as expensive as a dead crew,  especially one dead from a bad management decision"

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#261 2022-09-14 15:50:52

Calliban
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From: Northern England, UK
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Re: Earth to LEO - discuss

I am not a rocket engineer, but an air breathing space plane would appear to me to be an impractical concept, regardless of how it is designed.  At orbital velocity, the relative kinetic energy of the atmosphere hitting the plane at 17,500mph, will be about 30MJ/kg.  That is enough to covert it to plasma with temperature of several thousand Kelvin.  That is about 10x more energy than can be released by combustion of that same unit mass of air in the engines.  This would imply that the atmosphere will only provide net benefit as a source of propellant at much lower speeds than orbital velocity and at much lower altitudes than typical LEO.  Beyond a certain altitude, scramjet engines and wings are just dead weight that must be accelerated to orbital velocity.

Physics would seem to be against the idea of a single stage space plane and scramjet engines.  The idea looks better if the space plane is limited to the function of first stage, with relatively low peak speed and burn out altitude.  This would seem to be exactly the design philosophy behind air launch.  The plane is slow moving and flies at barely a few percent orbital altitude.  But it allows the rocket stage to ignite in the stratosphere where it achieves a better expansion ratio.  That boosts payload fraction and also allows aerodynamic considerations to relax somewhat.

Skylon was never going to work as a practical machine.  It was almost irrelevant what design decisions were made regarding the position of the engines, as the design goal was never going to be achievable for a real machine.  Air combusted in an engine, has a dHc of about 3MJ/kg.  It changes remarkably little regardless of what fuel is burned in it.  This means that at speeds greater than about 1500m/s, the frontal pressure of air on the engine inlet will begin to approach the thrust generated by the engine.  This woukd seem to be a hard limit for an airbreathing engine.  You might be able to squeeze a little more by virtue of the exhaust having lower molecular weight than the incoming air.  But I don't see how any airbreathing engine can be efficient at speeds greater than Mach 5-6.  The fundamental limit is imposed by the energy density of a fuel air mix.  If that energy density is lower than the kinetic energy of the same mass of air entering the engine, then the engines will generate net drag.  I cannot see a way around this, as even ramjets need to compress air into their combustion chambers.  This involves converting kinetic energy into pressure energy.

Last edited by Calliban (2022-09-14 16:10:22)


"Plan and prepare for every possibility, and you will never act. It is nobler to have courage as we stumble into half the things we fear than to analyse every possible obstacle and begin nothing. Great things are achieved by embracing great dangers."

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#262 2022-09-14 16:21:56

GW Johnson
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Re: Earth to LEO - discuss

Skylon's engines operated as a liquid air cycle airbreather only to Mach 5-ish speeds at only about 100,000 feet (30 km).  The rest of the way,  they were supposed to operate as LOX-LH2 rocket propulsion.

Prior studies have shown conclusively that 3 things are import to operating a 2-stage vehicle to LEO,  whether launched vertically or horizontally.  Those are speed at staging,  path angle at staging,  and altitude at staging.  Speed is the most important,  altitude the least. 

There is a very severe constraint regarding path angle:  if you cannot pull your 1st stage up to a path angle exceeding 45 degrees,  the second stage has to pull up steep before it can accelerate into the thinner air.  That's a big radius turn at high lifting gees,  which means large amounts of drag due to lift. 

The vertically-launched rocket is already at a very steep path angle at staging,  which relieves the second stage of some very severe design requirements,  and allows you to stage at a lower speed.

That high-altitude pull-up penalty is what Pegasus and similar have to fight,  and it is exactly why they have not been any more popular than they have been.  It really lowers deliverable payload to orbit if you do it that way.  But it is possible to do it that way.

The problem with airbreather-powered spaceplane concepts,  no matter how they are launched,  is the service ceiling problem that ALL (I repeat ALL !!!) airbreather-powered airplanes suffer from.  If the air is too thing,  (1) your available lift cannot exceed your path-normal weight component,  and may in fact be less,  and (2) your thrust (which is more or less proportional to the ambient air pressure) cannot exceed the sum of drag and the path-parallel weight component.  Weight does not scale down with air pressure.  Lift,  drag,  and airbreather thrust do!  You simply cannot accelerate or climb. 

At "only" hypersonic speeds,  that's about 100,000 to 130,000 feet (30-35 km) altitudes.  The far better choice of propulsion from there to orbital speeds is rocket.  And if you are using a rocket,  then why the hell are you down in the atmosphere facing drag,  when you could be doing a thrusted gravity turn in vacuum?

GW


GW Johnson
McGregor,  Texas

"There is nothing as expensive as a dead crew,  especially one dead from a bad management decision"

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#263 2022-09-14 17:04:10

Quaoar
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Re: Earth to LEO - discuss

GW Johnson wrote:

Skylon's engines operated as a liquid air cycle airbreather only to Mach 5-ish speeds at only about 100,000 feet (30 km).  The rest of the way,  they were supposed to operate as LOX-LH2 rocket propulsion.

Prior studies have shown conclusively that 3 things are import to operating a 2-stage vehicle to LEO,  whether launched vertically or horizontally.  Those are speed at staging,  path angle at staging,  and altitude at staging.  Speed is the most important,  altitude the least. 

There is a very severe constraint regarding path angle:  if you cannot pull your 1st stage up to a path angle exceeding 45 degrees,  the second stage has to pull up steep before it can accelerate into the thinner air.  That's a big radius turn at high lifting gees,  which means large amounts of drag due to lift. 

The vertically-launched rocket is already at a very steep path angle at staging,  which relieves the second stage of some very severe design requirements,  and allows you to stage at a lower speed.

That high-altitude pull-up penalty is what Pegasus and similar have to fight,  and it is exactly why they have not been any more popular than they have been.  It really lowers deliverable payload to orbit if you do it that way.  But it is possible to do it that way.

The problem with airbreather-powered spaceplane concepts,  no matter how they are launched,  is the service ceiling problem that ALL (I repeat ALL !!!) airbreather-powered airplanes suffer from.  If the air is too thing,  (1) your available lift cannot exceed your path-normal weight component,  and may in fact be less,  and (2) your thrust (which is more or less proportional to the ambient air pressure) cannot exceed the sum of drag and the path-parallel weight component.  Weight does not scale down with air pressure.  Lift,  drag,  and airbreather thrust do!  You simply cannot accelerate or climb. 

At "only" hypersonic speeds,  that's about 100,000 to 130,000 feet (30-35 km) altitudes.  The far better choice of propulsion from there to orbital speeds is rocket.  And if you are using a rocket,  then why the hell are you down in the atmosphere facing drag,  when you could be doing a thrusted gravity turn in vacuum?

GW

Hi, GW

Climbing a part, once in orbit, would Skylon have some trouble in atmospheric entry due to the shockwave between the engine nacelles on the tip of the wings?

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#264 2022-09-15 08:56:24

GW Johnson
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From: McGregor, Texas USA
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Re: Earth to LEO - discuss

Hi Quaoar:

Yeah,  it's called shock impingement heating,  and it did near-fatal damage to an X-15 back in 1968.  I covered that fatal risk to the Skylon parallel-nacelle design in post 260 above,  along with a lack of published solutions for the leading edge and nosetip problems. 

GW


GW Johnson
McGregor,  Texas

"There is nothing as expensive as a dead crew,  especially one dead from a bad management decision"

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#265 2022-09-15 17:29:07

Mars_B4_Moon
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Registered: 2006-03-23
Posts: 4,330

Re: Earth to LEO - discuss

I mirrored archived a pic by RobertDyck from another new mars discussion, DreamChaser based on HL-20 yet inspired by BOR-4  "Unpiloted Orbital Rocketplane" there was also a Dyna-Soar mockup

https://pic8.co/sh/UvdUuH.jpeg

The space plane that wasn’t: everything you never needed to know about Dyna-Soar
https://www.popsci.com/space-plane-wasn … dyna-soar/

Though the human side of Dyna-Soar was coming together, the program on the whole was starting to lose momentum. Early in 1962, the Air Force cancelled all development towards stage III, the multi-orbital phase of the program. Suborbital flights were next to go following a recommendation from Boeing. Then the military version of Dyna-Soar was cancelled. By spring, the hypersonic boost-glide vehicle had been restructured into nothing more than an orbital research program. This amendment was formalized in June when the DOD gave Dyna-Soar its secondary designation of X-20, putting it squarely in the growing list of experimental X-planes that would inform but never become large-scale production vehicles.

A full-scale mockup of the Dyna-Soar-turned-X-20 was unveiled at a press conference in Las Vegas in September of 1962 with the accompanying announcement that the DOD was funding the program with $130 million for 1963 and $125 million in 1964. But the good news was short-lived.

By 1963, NASA’s Mercury program was taking great strides having put two men into orbit on increasingly lengthy missions that were also answering questions earmarked for Dyna-Soar, namely questions of aerodynamic heating and human response to being in orbit. And the agency was also by this point firmly committed to using capsules for the Apollo lunar landing program. There was no way a Dyna-Soar-type vehicle would supersede the ballistic-type Apollo spacecraft already under development.

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#266 2022-09-15 17:58:51

SpaceNut
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Posts: 26,347

Re: Earth to LEO - discuss

Those are lifting body designs.

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#267 2022-09-21 12:05:06

Mars_B4_Moon
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Registered: 2006-03-23
Posts: 4,330

Re: Earth to LEO - discuss

Giant Centrifuge Startup That Wants to Hurl Things Into Space Raises $71 Mil

https://gizmodo.com/spinlaunch-funding- … 1849562787

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#268 2022-09-22 05:13:13

Mars_B4_Moon
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Registered: 2006-03-23
Posts: 4,330

Re: Earth to LEO - discuss

On the topic of Balloons there was this story in 2019

Balloon 'taxi service' to take satellites to space
https://www.bbc.com/news/uk-wales-49827415

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#269 2022-09-22 15:59:49

GW Johnson
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From: McGregor, Texas USA
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Posts: 4,933
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Re: Earth to LEO - discuss

There's not much difference between a lifting body and a true winged space plane during entry,  other than breaking up at too much angle of attack.  The main difference is at landing.  The winged craft are generally under 200 mph at touchdown,  and the lifting bodies considerably over 200 mph.  It's a real problem with lifting bodies.

By the way,  the old Space Shuttle was designed for 20-40 degree angle of attack during hypersonic entry.  Below 20 deg,  the hypersonic stream impacted the windscreen straight on.  Above 40 degrees,  same problem.  Windscreen fails in seconds under direct wind blast.  Only between 20 and 40 degrees was the windscreen "safe" in a separated flow zone.  Found that as a grad student in the UT Austin hypersonic wind tunnel,  confirmed later in hypersonic wind tunnel tests at AEDC. 

I'll give you one guess why the old X-20 Dyna-Soar design has a jettisonable heat shield over its windscreen. 

I'll give you one other guess why I think the SpaceX Starship will not survive entry very well with an exposed windscreen/set-of-windows at 60 deg angle of attack.

GW


GW Johnson
McGregor,  Texas

"There is nothing as expensive as a dead crew,  especially one dead from a bad management decision"

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#270 2022-09-22 21:46:01

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 26,347

Re: Earth to LEO - discuss

Oh, say it's not so just another reason; not support a crewed starships use.

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