Cheap Realistic Space Flight

Yeah, I wasn't really thinking of mixed propane/LOX in the breech. I
was thinking of something that would inject a ton of propane from the
projectile into three tons of LOX in the breech in a matter of
milliseconds. With good mixing. Time for another idea.

I'm interested in using simple low thrust/weight engines. These
require a long time to burn the fuel required for the delta-V
necessary. The long burn time, in turn, requires a staging velocity
(basically the gun muzzle velocity) of more than 2000 m/s or the
gravity losses get really bad.

As you say, methane-oxygen, at ~3450 m/s Ve, looks like a great gun
fuel -- cheap and decent sound velocity. But I think CH4-O2 in a pipe
is only going to get to 1700 - 2000 m/s. So I'm looking for some
low-tech trick to get the last 25%... something much simpler than
another rocket!

- One trick that might get part of the way there would be preheating the
CH4-O2 slug to get the initial sound velocity up. Obviously this
leads to a detonation problem, and I would bet that the higher the
initial fill pressure, the less you can preheat the slug. But I bet
heating the slug isn't too hard, and this might get 3-5%.

I think a travelling charge is inevitable to get the last 500 m/s.
But there is no need for a perfect solution here. If some of the
charge can be accelerated to 500 m/s or so while remaining compressed
and near the projectile, I think that's enough.

- Staged ignition of the gas slug (ignite the back first, work up
to the projectile) does not look workable to me. My simulations
show this leads to preposterously brutal shock waves smashing the
back of the projectile.

- One might enclose about half the gas slug in a tapering bag behind the
projectile. First the projectile is released and the gas outside the
bag ignited. About ten milliseconds later, the gas in the bag is
ignited. The idea is that the gas in the bag gets accelerated to
several hundred m/s before it ruptures. To do that, the bag has to
be fairly stiff. Note that since the gas in the bag weighs more
than the projectile, the bag doesn't have to take full acceleration
forces.

The propellant charge of a gas-phase gun is really big, so that it
takes a long time for release waves to cross the slug. For any given
barrel length, you can plot the amount of energy extracted from
successively larger propellant slugs, and it drops off because the
added rear propellant can't transfer energy to the forward propellant
fast enough.

- One advantage of the long tapering shape of the gas bag is that
you get to pull energy out of a much larger volume of propellant
slug at first. Another way of looking at it: the mean path that
the release wave takes is mostly radial rather than longitudinal,
and so is much shorter. This advantage applies to any projectile
with a large-area back face, but only for the initial portion of
the acceleration.

Fabricating and manipulating a barrel that can withstand the
pressure * area * time = momentum involved could be really tough.

- Rather than containing the firing pressure with steel strength (which
requires a LOT of steel, as Andy N. points out), one might try to
"contain" this pressure inertially/elastically, by making a relatively
thin spring steel barrel immersed in a large body of water. The idea
is to use the impedance of water to convert the short-lived pressure
spike into a short-lived radial expansion of the barrel. This idea
works really well with large barrels.

Of course, big barrels have the slow-release-wave problem, leading to
the intriguing question of whether there is a happy medium that
satifies both constraints. You can imagine multiple tapering gas bags
used to get the surface area up.

Also it would be good to find a way to damp the outgoing pressure wave
before it kills off a lot of nearby sea life. The energy in the wave
can be converted in to heat, but the momentum can only be spread
through more water and more time. The axpanding wave does the first
part. Maybe that's enough. Maybe spreading through time is going to
require stuff that collapses quickly under pressure, then expands
slowly (air bags?). Or maybe it's just a matter of putting the gun in
somewhat shallow water with a rough seabed that scatters the wave.

I'm looking for ways to model the effect of a few meters of sand
surrounding the barrel. I think wet sand should have higher impedance
than sea water, so long as there is very little air stuck in the
matrix. Higher impedance is good, because you can hold more pressure
for a given amount of radial expansion. Presumably large volumes of
wet sand or dirt is relatively easy to come by before you head out to
blue water.

(ed kyle) writes:

I could understand abandoning Saturn V once Apollo was over, but
shutting down Saturn IB never made any sense to me.

It didn't _have_ to make sense --- it was An Official Policy Decision
Made At The Highest Levels Of The U.S. Government (i.e., Nixon Himself)
that All The U.S.'s Federal Eggs Should Be Put In The Scuttle's Basket.
All the remaining Saturn hardware was therefore to be "expended," so that
There Would Be No Going Back.

Hence, the Skylab and Apollo/Soyuz programs, whose primary _political_ goals
were simply to "expend" the remaining Saturns and Apollos --- any science or
PR value was purely a secondary consideration.


-- Gordon D. Pusch

perl -e '$_ = \n"; s/NO\.//; s/SPAM\.//; print;'

Andrew Nowicki wrote in message ...
...
Stratospheric balloon is not the best platform because
it cannot go much higher than 40 km above sea level.

Air breathing airplanes fly only to 30 km, but
aircraft powered by electric motor can go much higher
than 30 km. (Leik Myrabo managed to fly a helicopter
powered by microwaves.)

Ion wind propulsion can theoretically work as high up as the lower
thermosphere. Lifters are currently just high voltage toys. But if the
efficiency and thrust/weight can be improved then a microwave powered
lifter might make a viable high altitude launch platform.

Oren

In article ,
Iain McClatchie wrote:
Yeah, I wasn't really thinking of mixed propane/LOX in the breech.

Just as well, since they don't mix. :-) Methane and LOX will mix in
any proportions, but propane and LOX are immiscible -- only a trace of
one will dissolve in the other. Vigorous agitation would mix them
momentarily, but left alone, they'd separate out again.
--
MOST launched 30 June; first light, 29 July; 5arcsec | Henry Spencer
pointing, 10 Sept; first science, early Oct; all well. |

(Gordon D. Pusch) wrote in message ...
(ed kyle) writes:

I could understand abandoning Saturn V once Apollo was over, but
shutting down Saturn IB never made any sense to me.

It didn't _have_ to make sense --- it was An Official Policy Decision
Made At The Highest Levels Of The U.S. Government (i.e., Nixon Himself)
that All The U.S.'s Federal Eggs Should Be Put In The Scuttle's Basket.
All the remaining Saturn hardware was therefore to be "expended," so that
There Would Be No Going Back.


Actually, Johnson was President when, two months before Apollo 7, in
mid-1968, NASA cancelled production of both Saturn 1B and Saturn V.

IMO it didn't matter who the President was - the vast costs
associated with Vietnam caused the cutbacks that led to the end of
Apollo and Saturn. Both political parties contributed to that
Southeast Asia experiment. But it was NASA itself that unwittingly
sacrificed Saturn IB by decisions it made in 1965/66. Then, NASA
shelved plans to develop Saturn IB/Centaur, which would have been
used to launch a pair of Mars landers then named Voyager, among
other things. Instead, NASA tried to move Voyager to Saturn V in
an attempt to keep that booster's production line running in the
face of the first Vietnam budget squeeze. In the end, NASA lost
Saturn IB, Saturn V, and Voyager. Later, it had to wastefully
start over and pay to develop another rocket, Titan IIIE, to
launch Viking (Mars) and the new Voyager (Jupiter/Saturn).

- Ed Kyle

In article ,
Gordon D. Pusch wrote:
I could understand abandoning Saturn V once Apollo was over, but
shutting down Saturn IB never made any sense to me.

It didn't _have_ to make sense --- it was An Official Policy Decision
Made At The Highest Levels Of The U.S. Government (i.e., Nixon Himself)...

No, not really. It was an official policy decision *approved* at the
highest levels of the government. The decision was actually made (subject
to approval higher up) by none other than NASA.

After, that is, their incredibly stupid attempt to get approval for
continued Saturn V operations *and* the shuttle *and* a space station
*and* a lunar base *and* a Mars expedition was shot down as an obvious
political non-starter.

(No, the Saturn IB wasn't on that list. The shuttle was originally meant
as essentially a reusable Saturn IB, a supply ship for the station. The
station itself would be launched by Saturn Vs.)

All the remaining Saturn hardware was therefore to be "expended," so that
There Would Be No Going Back.

No, there was considerable leftover Saturn hardware, and the theoretical
capability to launch it was retained for a while. That capability was
scrapped -- by NASA internal decision -- when it became clear that
retaining it was going to run up KSC costs substantially (at a time when
NASA was starved for cash) and that there was no chance of getting
political approval for doing anything with it.

Hence, the Skylab and Apollo/Soyuz programs, whose primary _political_ goals
were simply to "expend" the remaining Saturns and Apollos --- any science or
PR value was purely a secondary consideration.

No, Skylab considerably pre-dates all such decisions; its roots were in
post-Apollo planning in the mid-60s. Moreover, it did not expend all the
remaining Saturn Vs; it used only one of three. (Had there actually been
an explicit desire to use them all up, much the simplest way would have
been to fly Apollos 18 and 19 instead of canceling them.) Nor did Skylab
and Apollo-Soyuz use up all the Saturn IBs, or all the Apollos.
--
MOST launched 30 June; first light, 29 July; 5arcsec | Henry Spencer
pointing, 10 Sept; first science, early Oct; all well. |

In article ,
ed kyle wrote:
...But it was NASA itself that unwittingly
sacrificed Saturn IB by decisions it made in 1965/66. Then, NASA
shelved plans to develop Saturn IB/Centaur, which would have been
used to launch a pair of Mars landers then named Voyager, among
other things. Instead, NASA tried to move Voyager to Saturn V in
an attempt to keep that booster's production line running...

Not correct. The reason Voyager was moved to the Saturn V was that it
simply *outgrew* Saturn IB/Centaur, as a result of major weight growth
following Mariner 4's unpleasant revelations about the low density of the
Martian atmosphere. The alternatives were to lose most of the science
payload to make room for the bigger parachute and the braking rockets, or
else to start over and scale down the entire mission. Both were then
unthinkable. The Voyager people weren't happy about the move to the
Saturn V, but they really had no other option to preserve their project.

And they were then the only definite customer for Saturn IB/Centaur, so
their departure (plus NASA's strong desire to reduce the number of
different launchers it was developing) doomed it.
--
MOST launched 30 June; first light, 29 July; 5arcsec | Henry Spencer
pointing, 10 Sept; first science, early Oct; all well. |

(Henry Spencer) wrote in message ...
In article ,
ed kyle wrote:
...But it was NASA itself that unwittingly
sacrificed Saturn IB by decisions it made in 1965/66. Then, NASA
shelved plans to develop Saturn IB/Centaur, which would have been
used to launch a pair of Mars landers then named Voyager, among
other things. Instead, NASA tried to move Voyager to Saturn V in
an attempt to keep that booster's production line running...

Not correct. The reason Voyager was moved to the Saturn V was that it
simply *outgrew* Saturn IB/Centaur, as a result of major weight growth
following Mariner 4's unpleasant revelations about the low density of the
Martian atmosphere....


That was one of the stated reasons for stopping Saturn IB/Centaur, but
NASA's own history, SP-4212 "On Mars: Exploration of the Red Planet,
1958-1978", ("http://history.nasa.gov/SP-4212/contents.html") makes it
clear that money was the driving force behind the decision.

Begin Quote

(in mid 1965) NASA's "budget request for $5.26 billion yielded an
appropriation of $5.175 billion for fiscal year 1966. ... Voyager, as
a new start, was vulnerable, but other projects such as the adaptation
of the Centaur to the Saturn IB were also at risk, since such
development diverted money away from the completion of the Saturn V,
Apollo's
powerful booster. ... After several weeks of study, accompanied by
many leaks to the news media, NASA Headquarters officials announced in
mid-October 1965 that development of the Saturn IB-Centaur would be
terminated and that Voyager would be launched with ... Saturn V. ...

"The Saturn IB-Centaur combination was considered a diversionary
project by many managers, diverting monies that could be used for
the larger booster. Seamans wrote White House officials in late
1965 so that effect: "The development cost of combining Centaur with
Saturn IB would peak in FY 1966, 1967, 1968, while relatively little
vehicle development effort is required to use Saturn V.""

End Quote

The move to Saturn V doomed Mars Voyager by nearly doubling its costs.
In the end, the Titan IIIE Viking orbiter/lander combination massed
3330 kg versus the original 3175 kg for the Voyager orbiter/lander.
Could NASA have found a way to squeeze 155 kg more payload performance
out of Saturn IB/Centaur, or squeezed some mass out of Voyager? It
would have required a delay, but I think they could have done it.
Viking didn't make it to Mars until 1976 anyway. When Saturn
IB/Centaur
was cancelled, the Mars/Voyager missions were planned for 1971 and
1973.

And they were then the only definite customer for Saturn IB/Centaur,
so their departure (plus NASA's strong desire to reduce the number
of different launchers it was developing) doomed it.

Six Saturn IB/Centaur launches were planned (2 R&D and 4 Voyager).
Tentative plans called for future launches to Venus and the outer
planets and for 6-12 Saturn IB launches per year after 1968.

- Ed Kyle

(sci.space.history added to newsgroups list)

In article ,
ed kyle wrote:
Not correct. The reason Voyager was moved to the Saturn V was that it
simply *outgrew* Saturn IB/Centaur...

That was one of the stated reasons for stopping Saturn IB/Centaur, but
NASA's own history, SP-4212 "On Mars: Exploration of the Red Planet,
1958-1978", ("http://history.nasa.gov/SP-4212/contents.html") makes it
clear that money was the driving force behind the decision.
Begin Quote
(in mid 1965) NASA's "budget request for $5.26 billion yielded an
appropriation of $5.175 billion for fiscal year 1966. ... Voyager, as
a new start, was vulnerable, but other projects such as the adaptation
of the Centaur to the Saturn IB were also at risk, since such
development diverted money away from the completion of the Saturn V,
Apollo's powerful booster..."

And to continue that quote:

"The unfavorable budget was trouble enough without the additional bad news
brought by ... Mariner 4. The Martian atmosphere was much less dense than
previously estimated. All proposals for landing capsules had to be thrown
out... Given the 3000-kilogram launch weight for the spacecraft, much of
the scientific payload would have to be sacrificed... No matter which
approach to the problem was taken -- larger aeroshell, braking rockets,
larger parachutes -- it would mean too much weight for the Saturn IB."

While there was a lot of budget pressure weighing against continuation of
Saturn IB Centaur, it might have been resisted, had Voyager stayed within
that launcher's mass limits. The Mariner 4 atmosphere data was the fatal
blow: Voyager's case for keeping its own launcher was wrecked when it
outgrew that launcher. The advocates of Saturn IB Centaur previously had
successfully defended their choice against pressure from higher up, but
with Voyager unable to fly that way, they no longer had a leg to stand on,
and resistance to the outside pressures collapsed.

Whether a dense Martian atmosphere would have saved Saturn IB Centaur is
not clear. The pressures against it were strong. But the thin Martian
atmosphere was definitely what killed it.

The move to Saturn V doomed Mars Voyager by nearly doubling its costs.

"On Mars" again: "Considering the political climate, Voyager still might
have survived, but only if NASA were very careful about how it promoted
its planetary program. Unfortunately, the Manned Spacecraft Center in
Houston chose the first week of August 1967 to send 28 prospective
contractors a request for proposals to study a manned mission to Venus
and Mars... previous exercises of this kind ... had been billed as logical
extensions of the Voyager missions. This cast Voyager in the role of a
'foot in the door' for manned flights to the planets..."

Voyager was on thin ice already -- don't forget that summer 1967 was a
very bad time for the NASA budget in general, and that attempts to start
Voyager hardware development had already been postponed once by funding
shortages -- but it was political ineptitude by NASA that ultimately
killed it.

The greater costs of a Saturn V Voyager might someday have had an adverse
effect on the project, but in the end, Voyager never got far enough for
that to be a real issue.

In the end, the Titan IIIE Viking orbiter/lander combination massed
3330 kg versus the original 3175 kg for the Voyager orbiter/lander.

And Saturn IB Centaur's payload to Mars was 2700 kg. An overrun of nearly
500 kg is not something that could have been overcome trivially.

And they were then the only definite customer for Saturn IB/Centaur,
so their departure (plus NASA's strong desire to reduce the number
of different launchers it was developing) doomed it.

Six Saturn IB/Centaur launches were planned (2 R&D and 4 Voyager).
Tentative plans called for future launches to Venus and the outer
planets...

All under the Voyager program. No Voyager, no customers. Yes, there were
other program concepts that *might* have used it, but that counted for
little in the final decision.
--
MOST launched 30 June; first light, 29 July; 5arcsec | Henry Spencer
pointing, 10 Sept; first science, early Oct; all well. |

Case in point --
Government Regulations in the aftermath of September 11, 2001.

As applied to experimental rocketry, some of the media (notably in the EAA
websites) are asserting that tighter regulations of fuel canisters such as
the Estes model rockets may well cause the end of model rocketry.

--
Leonard C Robinson
"The Historian Remembers, and speculates on what might have been.
"The Visionary Remembers, and speculates on what may yet be."