tomcat,
Some math corrections that only seems to have turned out a bit more
fantastic than before, with each applied MJ worth of Radon ions
suggesting KE = 158e6 Kgf is getting into a level of nuclear thrust if
enough Radon(Rn222) gas can be supplied into the arrays of thrusters
without everything melting down upon the launch pad. Although this is
still purely mad-science speculation as based upon an theoretical ion
velocity of 150e3 km/s, though doing the math on just 150 km/s isn't
entirely without merit at delivering 158 Kgf/MJ.

However, I'll still have to totally agree that bigger is better.
Because you're absolutely right about what's new and always getting
improved about rocket engines and of the fuel they burn, and even SBRs
are getting into delivering more reliable bang for their tonnage. Per
usable volume of interior, the CNT spaceplanes of the future should
outperform the existing usable volume as provided by our NASA shuttle,
I'm thinking by at least 2:1 if not 4:1 seems doable.

Here's an improvement upon what a Radon ion thruster might suggest. I
must say that it's actually getting a little embarrassingly super
terrific as compared to Xenon, but that may be entirely related to my
math running amuck as suggesting far more ion velocity capability than
what's actually obtainable. But even if I'm only 0.1% right, it's still
going to offer an impressive number. First look at the proven Xenon/ion
method;

Xenon - Atomic Mass: 131.29 Amu
Xenon ION thrust exit velocity @30 km/s
http://www.daviddarling.info/encyclopedia/X/XIPS.html
"These investigations showed that xenon offered the highest thrust of
any non-reactive gas; Ions ejected by XIPS travel in a stream at a
speed of 30 km/s (62,900 mph), nearly 10 times that of a conventional
chemical thruster."

Unlike the non-reactive(dead) aspects of Xenon, obviously Radon(Rn222)
might otherwise be considered as a highly reactive form of gas, as such
it seems entirely possible that Radon ions should become nearly photon
ejected at half 'c', thus conceivably 150e3 km/s could be suggesting a
5000:1 exit velocity improvement, of which V2 should therefore
represent a rather impressive 25e6:1 improvement in the KE worth of
thrust potential and, Radon having the Amu of 222 is certainly much
denser than any Xenon Amu of 131.3, so as to start off with being worth
another 1.69:1

No matters what, besides the factor of Xe having to be just as
artificially obtained, sub-frozen and then highly insulated as a
sequestered sub-frozen mass of Xe, and of whatever mass of this Xe is
eventually going to run out, whereas accommodating a sufficient cash of
Radium(Ra226) that's creating Radon(Rn222) on the fly is good for a
half life of 1600 years.

Boeing 702: 25 centimeters in diameter = 165 mN of thrust
"Boeing Electron Dynamic Devices (702 Thruster), XIPS is 10 times more
efficient than conventional liquid fuel systems." The 702 offers an
individual range of power consumption up to 4.5 kW that obtains 3500
seconds/kg worth of Xenon ISP for creating 165 mN of thrust.

I'm certainly not the Radon(Rn222) ion thruster wizard but, I'm
thinking the amount of required energy as to ionize Rn222 that's
already somewhat on the go isn't going to be nearly as great as per the
none-reactive and thus passive Xenon. Therefore, the auxiliary power
source of electrons as being derived via PV cells, tether dipole or
that of an onboard reactor might be relatively slight on behalf of
energising ions from Radon.

See if my reverse engineering and not so great math is worth yet
another bad example:

Xenon ION thrust at 165e-3/4.5e3 = 36.666e-6 N per J

Based upon a 5000:1 increase in velocity represents a KE mutiplier
factor of 25e6

At good vacuum, Radon ION thrust 36.666e-6 * 25e6 * 1.69 = 1549 N per J

Thus a MJ applied for creating a Radon ION thrust might be good for
1549e6 N

The thrust per MJ in terms of Kgf becomes 1549e6 * 0.101972 = 157.95e6
Kgf

Obviously 158e6 Kgf of ION thrust per MJ of auxiliary applied energy
seems a bit much. Therefore perhaps the actual improvement in Ra222 ion
exit velocity isn't going to become worth the 5000:1 over the velocity
of Xenon ions, that is unless it somehow turns into a laser cannon form
of ion thruster, in which case the ion velocity improvement could reach
10,000:1. Otherwise if achieving just 150 km/s of ion thrust would cut
the results down to 158 Kgf/MJ, which still isn't all that bad.

This radon/ion notion still represents having a rather sizable cash of
which the spaceplane is having to haul Radium(Ra226) about, perhaps
several tonnes worth unless there's some viable method of expediting
the rate of decay into becoming Rn222. Possibly forcing the decay of
Ra226 within a reactor might suggest upon one method of generating the
onboard auxiliary energy at the same time as per expediting the
production of Rn222.

Otherwise having a continuously usable ISP of 3500 * 1600 years = 5.6e6
seems rather interesting. Not that using the basis of any kg worth of
Xenon under continuous usage is going to be good for more than an
hour/kg, therefore the actual Radium(Ra226)--Radon(Rn222) ISP
half-life gets this way further past the mark of 5.6e6 * 8.736e3 =
48.9e9

Of course, as per the added mass of the external basalt composite
shield which need not come and go from earth, as equally for the cash
of Radium(Ra226) tonnage need not be onboard for the launch or reentry
phase. Having robotically pre-launched the Radium and whatever reactor
and/or Radon(Rn222) extractor into orbit is the same logic as to having
the basalt composite shielding pre-established in orbit, thus why the
spaceplane need not physically carry the added mass upon launch or
reentry. However, since there's no apparent shortage of Radon(Rn222) to
being had upon Earth, this is why a good amount of that element as a
frozen gas (possibly as a liquid or solid) could be utilized as a
portion of their launch thrusting energy via ion thrusters, although
I'd expect that in addition to whatever terrestrial heavy lift
aerodynamic transporter as was utilized in the SS1 case, a few SBRs
would remain the norm if the large spaceplane launch mass is
essentially representing several hundred tonnes in need of exiting
Earth's gravity at 8 km/s.

If the LSE-CM/ISS were established, as then parking the spaceplane
along side this 50e6 tonne CM(counter mass) as having the 1e6 m3 ISS
within is just the best ever spaceplane depot/pitstop you can imagine,
providing a good 50t/m2 worth of physical and radiation shielding that
should take whatever the sun has to offer without measurably impacting
the spaceplane crew and passengers that would simply vacate their
moderately shielded ride and wait it out within that relative safety of
the CM/ISS.

In closing, I may not have fully considered the ramifications of
actually using Radon within our terrestrial environment, as I'm
re-thinking this Radon(Rn222) ion thruster might somehow represent a
situation that's somewhat like pumping out a whole lot better density
than lead at 150,000 km/s, whereas the down-wind of thruster exhaust
might become a wee bit lethal until the final decay of whatever volume
of Rn222 becomes actual lead, as for then whomever's still alive gets
to prematurely die from lead poising.
-

As per the usual, each and every day (as soon as my I get my PC
reconnected to this Usenet that sucks and blows, as such it's been
getting worse off than ever, as I seem to have attracted more than my
fair share of the almighty GOOGLE/NOVA V-Chip of automated seek and
destroy via spermware/malware as a gauntlet that's having been
specifically associated with my MI6/NSA Usenet interactions, thus
nearly always I'm having to frequently reboot because of their ongoing
efforts as to damage and/or eliminate my existence as far as my having
any public Usenet access or even so much as a working PC. This is still
the absolute ongoing truth and nothing but the truth that's easily 100%
provable, which seems only to further demonstrate that I'm essentially
right about most everything, thus apparently I'm worth targeting on
behalf of mainstream damage-control. The typical excuses that it's all
my fault, in that GOOGLE/NOVA and their partners of MI6/NSA in crimes
against humanity can't possibly avoid nor otherwise track a given
source of such spermware/malware, much less block it, is yet another
LLPOF proof-positive that I'm right about something that's apparently
not supposed to be public knowledge.
~

Kurt Vonnegut would have to agree; WAR is WAR, thus "in war there are
no rules" - In fact, war has been the very reason of having to deal
with the likes of others that haven't been playing by whatever rules,
such as GW Bush.
Life upon Venus, a township w/Bridge & ET/UFO Park-n-Ride Tarmac:
http://guthvenus.tripod.com/gv-town.htm
The Russian/China LSE-CM/ISS (Lunar Space Elevator)
http://guthvenus.tripod.com/lunar-space-elevator.htm
Venus ETs, plus the updated sub-topics; Brad Guth / GASA-IEIS
http://guthvenus.tripod.com/gv-topics.htm