Poll Which spacecraft do you think is the most realistic

[JackJL]

A non nuclear source for ludicrous energy density is metastable metallic hydrogen. This has a theoretical maximum Isp of 1400s and a specific density of just above water. At the moment metallic hydrogen has been created only once, for less than a second, and a metastable (i.e. storable) form may or may not exist.

This 1400s specific impulse is pretty close to the expert setting on the XR2, so combined with the scram jet it may be possible to reach orbit.

Of course even if it does exist in a nice storable & usable form, the tail is still going to be melted off and anyone within a mile will be deafened for an engine powerful enough to move this thing

 

[Sky Captain]

Yes reality is hard.

We will need a top gun enginer to make a exotic turbine helped hybrid scram engine (the turbine is only for low speed propultion).

And maybe asbestos enamels.

If it's possible of curse.

For that you are right. Only way to make chemical fueled reusable SSTO launcher with meaningful payload capability possible is to use engine which for significant part of the ascent uses atmospheric air as oxidizer.

See this

http://www.reactionengines.co.uk/skylon_overview.html

 

[tl8]

Thread reopened due to thoughtful and relevant discussion

 

[RisingFury]

I don't see metalic hydrogen as being a viable option for propulsion. It exists only extreme conditions and makiing an actual fuel tank that would constantly keep hydrogen under funky conditions would be insanelly difficult.

Also... how the hell do you burn that hydrogen then? Pressure in the engine would have to be just as insane...

 

[JackJL]

It's the metastable part that would help. If this form exists then the analogy is with diamond. Diamond is formed under crazy pressure, but when the pressure is removed the diamond doesn't explode (unless you can raise it's temperature over nearly 4000K).

If metastable metallic hydrogen can be formed so that it decomposes at a usable temperature one could granulate it or mix it with a fluid to store in a relatively normal tank. Just heat it when it hits the engine and it'll explode nicely.

By nicely I guess that any engine would melt if you tried to get any respectable thrust out of it.

 

[Urwumpe]

If metastable metallic hydrogen can be formed so that it decomposes at a usable temperature one could granulate it or mix it with a fluid to store in a relatively normal tank. Just heat it when it hits the engine and it'll explode nicely.

There are some many what ifs in it though. Starting that even the authors of the research paper admit that that metastable hydrogen might

a) not exist or
b) not have the claimed properties

Also the claimed meta-stable hydrogen will be even harder to store than slush hydrogen.

By nicely I guess that any engine would melt if you tried to get any respectable thrust out of it.

No, it is just a matter of power density, heat transfer and regenerative cooling. There is no written law that rocket engines have to loose 50% of their possible energy as heat. It is just that way currently. If you could just get closer to the theoretical limit of 66% effectivity for chemical rocket engines, you would already have a huge jump in specific impulse behind you.

 

[JackJL]

There's definitely a lot of what ifs! I'd say a nuclear thermal engine is more practical.

What I like about this technology is that it is not yet proved wrong even if it will turn out really impractical. In contrast with nuclear there is no need for a bulky reactor, so metallic hydrogen rockets may be scalable to jetpack size

I did some back of the envelope calculations a while back for a jetpack with this fuel - It would produce 2g (i.e. you would go up at 1g from earth's surface) for 120 seconds. This is enough to nudge you past the karman line!

(Made with some truly optimistic guesses about the weight of the engine)

 

[Urwumpe]

What I like about this technology is that it is not yet proved wrong even if it will turn out really impractical.

It is in science NEVER about proving something wrong, but about proving that something is true. Potential hypothetical rocket engines don't bring you anything and even if you could show that the warp drive is impossible, you have not gained anything yet.

 

[Sky Captain]

There's nothing "surprise" about a rocket launch. Moreover, using a manned spaceplane for such an action is complete overkill.

The advantage of manned spaceplane is it can be used for variety of missions like delivering crew to space station, testing new hardware, espionage, inspecting a spysat of your adversary. Also if it is the size of average fighter you could possibly hide the launch by taking off from aircraft carrier in the middle of nowere. Spaceplane could use its wings to perform lift assisted plane changes which would greatly help regarding suprise espionage missions.

 

[Urwumpe]

Also if it is the size of average fighter you could possibly hide the launch by taking off from aircraft carrier in the middle of nowere. Spaceplane could use its wings to perform lift assisted plane changes which would greatly help regarding suprise espionage missions.

Again, you can not hide it. A small rocket engine unleashes a few Megawatt more power than a large jet engine already, the trajectory even for a short ascent will bring you in the range of one of the MANY tracking stations all over the world and one you are in orbit, you will be picked up finally by automated space debris tracking networks.

And of course, your space plane will have to obey the laws of physics. TANSTAAFL.

 

[Sky Captain]

Still it would be better than spysats in terms of surprise. For example you take off from carrier in Indian ocean on a mission to overfly Iran. It might take some 20 minutes to complete the overflight which could be too short time to hide whatever Iran have to hide.

 

[Urwumpe]

Still it would be better than spysats in terms of surprise. For example you take off from carrier in Indian ocean on a mission to overfly Iran. It might take some 20 minutes to complete the overflight which could be too short time to hide whatever Iran have to hide.

And what do you think, will be visible on the images? after 20 minutes, you have not even vented the optics of residual atmosphere, or finished thermal conditioning. Also, you have not yet stabilized your orbit, so the accuracy of the images will be limited. Pretty much the same problems that prevented using the shuttle as fractional orbit spysat. It is not like you are talking about a new idea.

And which surprise? Oh my god hide the nuclear missiles, the USA are sending a spysat over us? Do you think ANY country in the world is wasting their time hiding stuff overground every time a spysat passes over the place? That is nice for novels, but today you have one spy sat passage every hour over a place. You couldn't even work overground that way.

You will put your stuff instead in bunkers, caves and high security factories, since you can't look through the roof. And put enough air defense stuff around them, so if a trigger-happy country like Israel decides to bomb the factory, they will not enjoy it.

 

[Sky Captain]

And what do you think, will be visible on the images? after 20 minutes, you have not even vented the optics of residual atmosphere, or finished thermal conditioning. Also, you have not yet stabilized your orbit, so the accuracy of the images will be limited. Pretty much the same problems that prevented using the shuttle as fractional orbit spysat. It is not like you are talking about a new idea.

And which surprise? Oh my god hide the nuclear missiles, the USA are sending a spysat over us? Do you think ANY country in the world is wasting their time hiding stuff overground every time a spysat passes over the place? That is nice for novels, but today you have one spy sat passage every hour over a place. You couldn't even work overground that way.

You will put your stuff instead in bunkers, caves and high security factories, since you can't look through the roof. And put enough air defense stuff around them, so if a trigger-happy country like Israel decides to bomb the factory, they will not enjoy it.

So then Dynasoar would`t have worked as a rapid response spysat. That`s where I get the idea of surprise espionage overflights since it was mentioned it could use atmospheric lift to perform orbital plane changes to get unexpectedly over target area.

 

[Urwumpe]

So then Dynasoar would`t have worked as a rapid response spysat. That`s where I get the idea of surprise espionage overflights since it was mentioned it could use atmospheric lift to perform orbital plane changes to get unexpectedly over target area.

Yes, but Dynasoar was created at an era, when you had not been aware of the images before the film capsule got retrieved and when the number of spy satellites had been about 4-6 active at a time. Today you have about 20 active in the whole NATO. And instead of film capsules, high-speed data links over military communication satellites return the data in encrypted form in seconds.

 

[chourave]

The most important reason about why a delta glider like space plane will be create is Man need toy.

After we can find some use for this toy.

A lot of satellite weight less than 200 kilo. This simply mean if you carry a satellite you will take only 3 passenger.