Re: How Rockets Differ From Jets


Brad Guth wrote:
> tomcat (aka "How Rockets Differ From Jets"),
> One minute worth of had aerobreaking doesn't seem all that
> insurmountable, as I was thinking of your CNT covered basalt composite
> Spaceplane taking 10 minutes for this transition.


>>From orbit (17,500 mph) 1 minute of aerobreaking should be all that is
needed. From a 'slingshot' planetary return (100,000 mph) 2 minutes of
hard (emergency breaking) will be needed.

The 'emergency breaking' consisting of the Corelle slabs that jut up
and the top of the spaceplane and down on the bottom, as well as normal
air brakes, split rudder and split ailerons.

If enough fuel remains then a retrofire should be used. In 'retrofire'
the spaceplane, still outside the atmosphere, turns around and gives
full thrust for a given amount of time, then it turns around again for
reentry.

Another option is 'reverse thrust' where the ship uses thrust vectoring
or auxiliary engines, bottom thrusters with thrust vectoring or ion
engines with thrust vectoring, to thrust after entering the atmosphere.
Engines could even be mounted in the front for the sole purpose of
'reverse thrust' or a 'retrofire' where the spaceplane doesn't have to
do the turn around maneuver.


> >Disposable parachute is a bit extreme and does not take into account
> >the enormous G forces generated by slowing down . . . instantly. It
> >will take a shovel to remove the astronauts.
> I like the part about using a "shovel to remove the astronauts".
> However, I wasn't exactly thinking about deploying a 10,000 m2 worth of
> aerobreaking ceramic parachute, more like a 100 m2 for a given 300
> tonne Spaceplane that should get the astronaut removal tool down to
> using a fork and spoon rather than a shovel. The parachute need not be
> parachute shaped, rather more or less a sphere or that of a reverse
> teardrop form of a ceramic aerobreaking drag inducing anchor.


The simpler the spaceplane the better. Remember 'Murphy's Law'. It
works overtime on complex, Rube Goldberg, contraptions. If a hatch has
to open, it might fail. If 'something' has to deploy, it might fail.
If a rendevouz is necessary, it might fail. If exploding bolts are
used, they might fail.

In 1969 they had to go Rube Goldberg on the Apollo missions because of
limited and marginal technology.

Today we don't have to do: 'docking', 'separation', 'deployments',
'jettisons', 'EVA's', 'rotations', 'orbits', 'checklists', 'telemetry',
'landers', etc. Just build one nice simple spaceplane.


> >The cooling from the hydrogen fuel is essential for both the hull and
> >interior. Unless, of course, you like a 1000 deg. F. cockpit with only
> >your nomex flight suit between you and . . . cremation. That is what I
> >meant when I said: hot, hot, hot.
> Even 10 minutes worth of being within the externally "hot, hot, hot"
> mode isn't going to get the interior of your CNT and Corelle coated
> Spaceplane at more than a dry 50 deg. F rise (it's called
> thermaldynamics of energy-in = energy-out), meaning it takes time for
> thermal energy to transfer. Of course the greater the mass that's
> situated between whatever's hot and what's not is working in your
> favor. If systems and the crew and passengers can't take that sort of a
> dry-heat licking and keep on ticking, then what's the point?
>
> There's no such thing as achieving a zero thermal rise within the
> Spaceplane interior. Thus why are you insisting upon achieving that
> goal via the brute force and extremely volumetric inefficient method of
> using LH2?

You are wrong about thermal. There are calculations on hypersonic air
friction heating. Back in the 70's the predicted heat was so high they
thought the calculations were in error. They were not. If anything,
the heat is worse than predicted.

This might explain the use of aluminum (approx. 1000 deg. F. meltpoint)
on the shuttle instead of spending more and using titanium (approx.
2000 deg. F. meltpoint).

The Shuttle can experience as much as 7000 deg. F. on it's skin during
reentry from orbit. This is not just a little 'plasma' heat, nor is it
a quick pass the hand through the candle trick. It is turn metal into
watery liquid, in seconds, kind of heat. It is a 'melt the interior'
kind of heat. It is barbeque the pilot kind of heat. Take it
seriously.

> BTW; what's the other point in using such a low density product such as
> Hydrogen?
> Even LH2 is wossy density and, it'll take up 75% of the Spaceplane
> interior in order to safely store enough of it to do any good. Between
> your LH2, LO2 plus accommodating a great deal of systems, you'll be
> lucky to having 10% usable interior. Is less than 10% usable volume
> your goal? How about if there's only 5% remaining for the crew,
> apssengers and whatever other payload, is that still going to fly?


The spaceplane is a 'flying gas can'. About 95% of it's wet GLOW
(Gross Lift Off Weight) will be fuel. The 'dry weight' of the
spaceplane must be so light you have to tether it down.

The spaceplane must be big enough so that 10% usable interior is large
enough for cargo and crew.

The new 'slush' tanks where liquid hydrogen is super compressed to a
slush-like state will allow twice as much hydrogen in the tanks than
before. This fairly new technology is one of the main reasons I am
supporting the building of a SSTO and SSTP immediately.

> If that Spaceplane core structure was of the basalt composite, along
> with a few outer layers of CNT and as then having the brute-force
> firewall as being your primary thermal shield of that Corelle should do
> just fine and dandy without extra cooling. Remember it there's
> artificially induced cooling involved, the a great dela of differential
> will have to be within spec of one part geets extremely hot while the
> other connecting part(s) remain extremely cold.

See my remarks above on hypersonic thermal heat. Read my lips: you
will need cryogenic liquids to keep you cool during hypersonic
atmospheric flight.

The only exception would be if 'air spikes', electronic gizmos that can
knock air molecules away from the hull, are perfected to the point that
they really work. Then you would have the spaceplane surrounded by a
vacuum even when moving at hypersonic velocity in the atmosphere.

> A Radium(Ra226) reactor at extreme pressure is already providing a
> viable resource of easily refrigerated Radon. Do you not appreciate the
> terrific density and thermal dynamics of Radon phase change and thus
> thermal transfer that Rn222 can provide?
>
> An accumulator/reactor cell of such highly pressurised radon is going
> to be capable of supplying more viable heat transfer than even your
> imagination can imagine. Then whatever's pre-heated Radon gets utilized
> within fairly powerful ION thrusters. What's not to like?

I 'like' the idea of ion thrusters. And, you have just pointed out
that they could help with a 'retrofire' and 'reverse thrust' which are
very important.

Remember, however, that stopping a spaceplane going 200,000+ mph takes
a lot of stopping. Even if you slow to 50,000 mph or less the reentry
air friction heat will be . . . tremendous.
>
> >This would help a lot returning from Venus at 200,000 mph because of a
> >good slingshot, finding out you had a hydrogen leak, and enable you to
> >stop quick in the atmosphere so you don't have to listen to your face
> >bubble and fry like bacon in hot grease.
> Why "slingshot"?

Slingshots enable you to 'borrow' energy from a planetary body for
greatly increased speed. You use the gravity of the body to do a
twirl, turning you around without braking, and using the forward motion
of that body to boost you many thousands of mph.

> I could help redesign your Spaceplane into being a multitasking
> rigid-airship, or I could give the payload a viable rigid-airshelp that
> could be quite easily deployed as you slingshot yourself about Venus in
> order to head back towards mother Earth ASAP, that which if all goes
> well could still be within 100e6 km of Venus by the time your high
> velocity Spaceplane touches down upon your home tarmac. Of course, if
> you're insisting upon waiting around untill the entire Spaceplane can
> be affordably constructed out of CNT, in which case decades from now
> you'll still be in R&D and bankrupt to boot, as either China, Russia or
> perhaps even India/ESA are going to have established their one and only
> LSE-CM/ISS, as well as having been there and done the Venus thing.

A ridgid airship is precisely what a well built spaceplane is. Our
'design engineers' don't seem to understand that. If you don't have to
tether down the dry weight vehicle so it doesn't float off, then those
engineers haven't done their jobs.

You and I know this, but you can't get it through some people's thick
heads that you have to lighten the load on aeronautical and space
vehicles. They haven't heard of lighter elements or vacuum, either
one. They insist on using steel which is too heavy and aluminum which
melts.

Believe me, you and I know that spaceplanes have to be ridgid airships,
but we are the only ones that know this. The others haven't figured it
out.

This is why 'they' scream and shout "impossible!", "it can't be done!",
"you're anti-NASA!", "you don't know what you are saying", "Oh no, this
is crazy!", "we need parachutes!", "only capsules will work!", "it will
take 12 years!".

Actually it will take them -- forever -- because they don't know how
to build a 'simple' ridgid airship spaceplane designed to take the
heat.

Think light and think hot, hot, hot. Also, think SSME's because . . .
they work. I like things that work.


tomcat

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