A kerosene-fueled X-33 as a single stage to orbit vehicle. [Physics]

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From: Robert Clark on 13 Nov 2009 19:58

The proposal was to transform the X-33 into a reusable, orbital
vehicle using NK-33 engines. The NK-33 was a Russian 1960's era engine
so I thought they would have to be taken out of mothballs for the
purpose. But I recently found that Aerojet is working with the NK-33
engines to be used on Orbital Sciences Taurus 2 launcher:

08/31/09 10:15 AM ET
Aerojet Looking to Restart Production of NK-33 Engine.
By Amy Klamper
http://www.spacenews.com/launch/aerojet-looking-restart-production-nk-33-engine.html

August 19, 2009
Russian Mail-Order Ride.
http://blogs.airspacemag.com/daily-planet/2009/08/19/russian-mail-order-ride/

Aerojet has already purchased several of the engines, and is debating
whether to start it's own production lines or to use Russian
production for future purchases of the engine. Then the Air Force or
NASA could use these to make a reusable, single-stage-to-orbit vehicle
and near term, at least for a prototype vehicle. There was some debate
on the Augustine commission if NASA and the U.S. should use Russian
engines for a significant portion of their launches, but this
complaint might be ameliorated in regards to the NK-33 if production
lines were started in the U.S.
A question would be of the payload it could carry. The preliminary
calculations I made suggested it might just make orbit, so likely it
would have low payload capability. Some possibilities to increase the
payload might be to densify the kerosene propellant by subcooling to
near LOX temperatures or to use more energetic hydrocarbon
propellants. The densification would allow it carry more propellant.
Some possible energetic hydrocarbon propellants are suggested here:

Alternate Propellants for SSTO Launchers.
Dr. Bruce Dunn
http://www.dunnspace.com/alternate_ssto_propellants.htm

Another possible method to increase payload would to use a version of
the NK-33 with an aerospike nozzle. This would allow it to have higher
Isp at sea level.

It should also be possible to use the hydrocarbon fueled X-33 as the
a reusable first stage booster. The Air Force is investigating such
boosters as a means of cutting costs to space. Since the reconfigured
X-33 would be able to reach orbit at 21,700 kg dry mass, it could be
able to lift in the range of a few thousand kg's payload as the first
stage of two stage-to-orbit-system.

Bob Clark

On Nov 1, 8:20 am, Robert Clark <rgregorycl...(a)yahoo.com> wrote:
> Table of Contents.
> I.)Introduction.
> II.)Lightweight propellant tanks.
> III.)Kerosene fuel and engines for the X-33/Venture star.
> IVa.)Aerodynamic lift applied to ascent to orbit.
> b.)Estimation of fuel saving using lift.
> V.)Kerosene fueled VentureStar payload to orbit.
>
> I.) A debate among those questing for the Holy Grail of a reusable,
> single-stage-to-orbit vehicle is whether it should be powered by
> hydrogen or a dense hydrocarbon such as kerosene. Most concepts for
> such a vehicle centered on hydrogen, since a hydrogen/LOX combination
> provides a higher Isp. However, some have argued that dense fuels
> should be used since they take up less volume (equivalently more fuel
> mass can be carried in the same sized tank) so they incur less air
> drag and also since the largest hydrocarbon engines produce greater
> thrust they can get to the desired altitude more quickly so they also
> incur lower gravity drag loss.
> Another key fact is that for dense fuels the ratio of propellant mass
> to tank mass is higher, i.e., you need less tank mass for the same
> mass of propellant. This fact is explored in this report:
>
> Single Stage To Orbit Mass Budgets Derived From Propellant Density and
> Specific Impulse.
> John C. Whitehead
> 32nd AIAA/ASME/SAE/ASEE Joint Propulsion ConferenceLake Buena Vista,
> FLJuly 1-3, 1996http://www.osti.gov/bridge/servlets/purl/379977-2LwFyZ/webviewable/37...
>
> Whitehead notes that the propellant mass to tank mass ratio for
> kerosene/LOX is typically around 100 to 1, while for liquid hydrogen/
> LOX it's about 35 to 1, which would result in a significantly greater
> dry mass for the hydrogen-fueled case just in tank weight alone. Based
> on calculations such as these Whitehead concludes the best option for
> a SSTO would be to use kerosene/LOX.
> The case for the X-33/VentureStar is even worse because the unusual
> shape of the tanks requires them to use more tank mass than a
> comparably sized cylindrical tank. This is discussed here:
>
> Space Access Update #91 2/7/00.
> The Last Five Years: NASA Gets Handed The Ball, And Drops It.
> "...part of L-M X-33's weight growth was the "multi-
> lobed" propellant tanks growing considerably heavier than promised.
> Neither Rockwell nor McDonnell-Douglas bid these; both used proven
> circular-section tanks. X-33's graphite-epoxy "multi-lobed" liquid
> hydrogen tanks have ended up over twice as heavy relative to the
> weight of propellant carried as the Shuttle's 70's vintage aluminum
> circular-section tanks - yet an X-33 tank still split open in test
> last fall. Going over to aluminum will make the problem worse; X-
> 33's aluminum multi-lobed liquid oxygen tank is nearly four times as
> heavy relative to the weight of propellant carried as Shuttle's
> aluminum circular-section equivalent."http://www.space-access.org/updates/sau91.html
>
> The X-33's twin liquid hydrogen tanks had a weight of 4,600 pounds
> each, and the liquid oxygen tank a weight of 6,000 pounds, for total
> of 15,200 pounds for the tanks:
>
> Marshall Space Flight Center
> Lockheed Martin Skunk Works
> Sept. 28, 1999
> X-33 Program in the Midst of Final Testing and Validation of Key
> Components.http://www.xs4all.nl/~carlkop/x33.html
>
> The weight of the propellant carried by the X-33 was supposed to be
> 210,000 lb. So the propellant to tank mass ratio for the X-33 was only
> about 14 to 1(!). This would be a severe problem for the full-scale
> VentureStar. Its gross lift off weight was supposed to be 2,186,000
> lbs with a fuel weight of 1,929,000 lbs:
>
> X-33 Advanced Technology Demonstrator.http://teacherlink.ed.usu.edu/tlnasa/OtherPRINT/Lithographs/X33.Advan...
>
> So the VentureStar would have a dry mass of 257,000 lbs. Since the
> same design would be used for the VentureStar tanks as those of the
> X-33, the propellant mass to tank mass ratio would also be 14 to 1, so
> the tank mass would be 138,000 lbs. But this means the empty tank mass
> alone would be over half of the vehicle's dry weight (!)
> It would have been extremely difficult for the VentureStar to have
> made orbit with such a large weight penalty from the start. From all
> accounts the weight problem with the tanks drove other problems such
> as the need to add larger wings, increasing the weight problem
> further. NASA wound up canceling the program when Lockheed couldn't
> deliver the working liquid hydrogen tanks even at this excessive
> weight. However, rather than canceling the program I believe the
> better course would have been to open up competition for coming up
> with alternative, creative solutions for reducing the weight of the
> tanks. This would also have resolved some of the problems with the
> vehicles weight growth.
>
> II.) I have proposed one possibility for lightweighting the X-33 tanks
> on this forum:
>
> http://www.bautforum.com/space-exploration/86728-passenger-market-sub...
>
> The idea would be to achieve the same lightweight tanks as
> cylindrical ones by using multiple, small diameter, aluminum
> cylindrical tanks. You could get the same volume by using varying
> lengths and diameters of the multiple cylinders to fill up the volume
> taken up by the tanks. The cylinders would not have to be especially
> small. In fact they could be at centimeter to millimeter diameters, so
> would be of commonly used sizes for aluminum tubes and pipes.
> The weight of the tanks could be brought down to the usual 35 to 1
> ratio for propellant to tank mass. Then the mass of the tanks on the
> X-33 would be 210,000 lbs/35 = 6,000 lbs, saving 9,200 lbs off the
> vehicle dry weight. This would allow the hydrogen-fueled X-33 to
> achieve its original Mach 15 maximum velocity.
> The same idea applied to the full-scale hydrogen-fueled VentureStar
> would allow it to significantly increase its payload carrying
> capacity. At a 35 to 1 ratio of propellant mass to tank mass, the
> 1,929,000 lbs propellant mass would require a mass of 1,929,000/35 =
> 55,000 lbs for the tanks, a saving of 83,000 lbs off the original tank
> mass. This could go to extra payload, so from 45,000 lbs max payload
> to 128,000 lbs max payload.
> An analogous possibility might be to use a honeycombed structure for
> the entire internal makeup of the tank. The X-33's carbon composite
> tank was to have a honeycombed structure for the skin alone. Using a
> honeycomb structure throughout the interior might result in a lighter
> tank in the same way as does multiple cylinders throughout the
> interior.
> Still another method might be to model the tanks standing vertically
> as conical but with a flat front and back, and rounded sides. Then the
> problem with the front and back naturally trying to balloon out to a
> circular cross section might be solved by having supporting flat
> panels at regular intervals within the interior. The X-33 composite
> tanks did have support arches to help prevent the tanks from
> ballooning but these only went partially the way through into the
> interior. You might get stronger a result by having these panels go
> all the way through to the other side.
> These would partition the tanks into portions. This could still work
> if you had separate fuel lines, pressurizing gas lines, etc. for each
> of these partitions and each got used in turn sequentially. A
> preliminary calculation based on the deflection of flat plates under
> pressure shows with the tank made of aluminum alloy and allowing
> deflection of the flat front and back to be only of millimeters that
> the support panels might add only 10% to 20% to the weight of the
> tanks, while getting similar propellant mass to tank mass ratio as
> cylindrical tank. See this page for an online calculator of the
> deflection of flat plates:
>
> eFunda: Plate Calculator -- Simply supported rectangular plate with
> uniformly distributed loading.http://www.efunda.com/formulae/solid_mechanics/plates/calculators/SSS...
>
> Note you might not need to have a partitioned tank, with separate
> fuel lines, etc., if the panels had openings to allow the fuel to pass
> through. These would look analogous to the wing spars in aircraft
> wings that allow fuel to pass through. You might have the panels be in
> a honeycomb form for high strength at lightweight that still allowed
> the fuel to flow through the tank. Or you might have separate beams
> with a spaces between them instead of solid panels that allowed the
> fuel to pass through between the beams.
> Another method is also related to the current design of having a
> honeycombed skin for the composite hydrogen tanks. Supposed we filled
> these honeycombed cells with fluid. It is known that pressurized tanks
> can provide great compressive strength. This is in fact used to
> provide some of the structural strength for the X-33 that would
> otherwise have to be provided by heavy strengthening members. This
> idea would be to apply fluid filled honycombed cells. However, what we
> need for our pressurized propellant tanks is *tensile strength*.
> A possible way tensile strength could be provided would be to use the
> Poisson's ratio of the honeycombed cells:
>
> Poisson's ratio.http://en.wikipedia.org/wiki/Poisson%27s_ratio
>
> Poisson's ratio refers to the tendency of a material stretched in one
> direction to shrink in length in an orthogonal direction. Most
> isotropic solid materials have Poisson's ratio of about .3. However,
> the usual hexagonal honeycombed structure, not being isotropic, can
> have Poisson's ratios in the range of +1. This is mentioned in this
> article about non-standard honeycombed structures that can even have
> negative Poisson ratios:
>
> Chiral honeycomb.http://silver.neep.wisc.edu/~lakes/PoissonChiral.html
>
> However, note that from the formula for the volumetric change in the
> Wikipedia Poisson's ratio page, a stretching of a material with a +1
> Poisson's ratio implies a *decrease* in volume; actually this is true
> for any case where the Poisson's ratio is greater than +.5. Then fluid
> filled honeycombed cells would resist the stretching of tensile strain
> by the resistance to volume compression. This would be present with
> both gases and liquids. Gases are lighter. ...
>
> read more »

From: Robert Clark on 15 Nov 2009 02:14

From: Pat Flannery on 15 Nov 2009 07:53

Robert Clark wrote:
> Aerojet claims their version of the NK-33 is "fully reusable":
>
> Space Lift Propulsion.
> http://www.aerojet.com/capabilities/spacelift.php
>
> Anyone have any idea how many reuses they mean by that?

NK-33 engines were designed for a total burn time of 1,200 seconds (20
minutes): http://www.astronautix.com/engines/nk33.htm

Pat

From: Robert Clark on 21 Nov 2009 09:59

On Nov 13, 7:58 pm, Robert Clark <rgregorycl...(a)yahoo.com> wrote:
> The proposal was to transform the X-33 into a reusable, orbital
> vehicle using NK-33 engines. The NK-33 was a Russian 1960's era engine
> so I thought they would have to be taken out of mothballs for the
> purpose. But I recently found that Aerojet is working with the NK-33
> engines to be used on Orbital Sciences Taurus 2 launcher:
>
> 08/31/09 10:15 AM ET
> Aerojet Looking to Restart Production of NK-33 Engine.
> By Amy Klamperhttp://www.spacenews.com/launch/aerojet-looking-restart-production-nk...
>
> August 19, 2009
> Russian Mail-Order Ride.http://blogs.airspacemag.com/daily-planet/2009/08/19/russian-mail-ord...
>
> Aerojet has already purchased several of the engines, and is debating
> whether to start it's own production lines or to use Russian
> production for future purchases of the engine. Then the Air Force or
> NASA could use these to make a reusable, single-stage-to-orbit vehicle
> and near term, at least for a prototype vehicle. There was some debate
> on the Augustine commission if NASA and the U.S. should use Russian
> engines for a significant portion of their launches, but this
> complaint might be ameliorated in regards to the NK-33 if production
> lines were started in the U.S.
> A question would be of the payload it could carry. The preliminary
> calculations I made suggested it might just make orbit, so likely it
> would have low payload capability. Some possibilities to increase the
> payload might be to densify the kerosene propellant by subcooling to
> near LOX temperatures or to use more energetic hydrocarbon
> propellants. The densification would allow it carry more propellant.
> Some possible energetic hydrocarbon propellants are suggested here:
>
> Alternate Propellants for SSTO Launchers.
> Dr. Bruce Dunnhttp://www.dunnspace.com/alternate_ssto_propellants.htm
>
> Another possible method to increase payload would to use a version of
> the NK-33 with an aerospike nozzle. This would allow it to have higher
> Isp at sea level.
>
> It should also be possible to use the hydrocarbon fueled X-33 as the
> a reusable first stage booster. The Air Force is investigating such
> boosters as a means of cutting costs to space. Since the reconfigured
> X-33 would be able to reach orbit at 21,700 kg dry mass, it could be
> able to lift in the range of a few thousand kg's payload as the first
> stage of two stage-to-orbit-system.
>

The same reconfiguration of the Lockheed version of the X-33 to dense
fuels and engines to transform it into a full orbital vehicle would
also work for the other proposed half-scale suborbital demonstrators.
The McDonnell-Douglas version was essentially the DC-X, scaled
somewhat larger. See the linked image. I don't know how much the McD-D
version of the X-33 would have cost. However, according to this
Astronautix page a 1/2-scale version of the full orbital DC-Y had been
proposed, but not funded, which would have cost in the range $450
million, compared to the $60 million of the DC-X, in 1990's dollars:

DC-X2.
http://astronautix.com/lvs/dcx2.htm

This would have just below suborbital to suborbital performance, but
the price would be significantly less than the DC-Y full orbital
version of $5 billion:

DC-Y.
http://astronautix.com/lvs/dcy.htm

However, the point is some preliminary calculations show this 1/2-
scale DC-X2 should be able to carry enough dense hydrocarbon fuel
under such a reconfiguration to reach orbit. So you would be able to
get a reusable SSTO prototype at a significantly reduced price than
the $5 billion suggested for the full DC-Y vehicle program.

Bob Clark

Figure 5: X-33 Concept Art from McDonnell Douglas (Frassanito, J.,
McDonnell Douglas).
http://vorlon.case.edu/~jam64/images/SSTO/SSTO_Figure_5.jpg

taken from:

Single Stage to Orbit:
A Reliable Transport System or an Unattainable Dream?
http://vorlon.case.edu/~jam64/work/ssto.htm

From: Robert Clark on 24 Nov 2009 03:42

On Nov 21, 9:59 am, Robert Clark <rgregorycl...(a)yahoo.com> wrote:
> On Nov 13, 7:58 pm, Robert Clark <rgregorycl...(a)yahoo.com> wrote:

> > The proposal was to transform the X-33 into a reusable, orbital
> > vehicle using NK-33 engines. The NK-33 was a Russian 1960's era engine
> > so I thought they would have to be taken out of mothballs for the
> > purpose. But I recently found that Aerojet is working with the NK-33
> > engines to be used on Orbital Sciences Taurus 2 launcher:
>
> > 08/31/09 10:15 AM ET
> > Aerojet Looking to Restart Production of NK-33 Engine.
> > By Amy Klamperhttp://www.spacenews.com/launch/aerojet-looking-restart-production-nk...
>
> > August 19, 2009
> > Russian Mail-Order Ride.http://blogs.airspacemag.com/daily-planet/2009/08/19/russian-mail-ord...
>
> > Aerojet has already purchased several of the engines, and is debating
> > whether to start it's own production lines or to use Russian
> > production for future purchases of the engine. Then the Air Force or
> > NASA could use these to make a reusable, single-stage-to-orbit vehicle
> > and near term, at least for a prototype vehicle. There was some debate
> > on the Augustine commission if NASA and the U.S. should use Russian
> > engines for a significant portion of their launches, but this
> > complaint might be ameliorated in regards to the NK-33 if production
> > lines were started in the U.S.
> > A question would be of the payload it could carry. The preliminary
> > calculations I made suggested it might just make orbit, so likely it
> > would have low payload capability. Some possibilities to increase the
> > payload might be to densify the kerosene propellant by subcooling to
> > near LOX temperatures or to use more energetic hydrocarbon
> > propellants. The densification would allow it carry more propellant.
> > Some possible energetic hydrocarbon propellants are suggested here:
>
> > Alternate Propellants for SSTO Launchers.
> > Dr. Bruce Dunnhttp://www.dunnspace.com/alternate_ssto_propellants.htm
>
> > Another possible method to increase payload would to use a version of
> > the NK-33 with an aerospike nozzle. This would allow it to have higher
> > Isp at sea level.
>
> > It should also be possible to use the hydrocarbon fueled X-33 as the
> > a reusable first stage booster. The Air Force is investigating such
> > boosters as a means of cutting costs to space. Since the reconfigured
> > X-33 would be able to reach orbit at 21,700 kg dry mass, it could be
> > able to lift in the range of a few thousand kg's payload as the first
> > stage of two stage-to-orbit-system.
>
> The same reconfiguration of the Lockheed version of the X-33 to dense
> fuels and engines to transform it into a full orbital vehicle would
> also work for the other proposed half-scale suborbital demonstrators.
> The McDonnell-Douglas version was essentially the DC-X, scaled
> somewhat larger. See the linked image. I don't know how much the McD-D
> version of the X-33 would have cost. However, according to this
> Astronautix page a 1/2-scale version of the full orbital DC-Y had been
> proposed, but not funded, which would have cost in the range $450
> million, compared to the $60 million of the DC-X, in 1990's dollars:
>
> DC-X2.http://astronautix.com/lvs/dcx2.htm
>
> This would have just below suborbital to suborbital performance, but
> the price would be significantly less than the DC-Y full orbital
> version of $5 billion:
>
> DC-Y.http://astronautix.com/lvs/dcy.htm
>
> However, the point is some preliminary calculations show this 1/2-
> scale DC-X2 should be able to carry enough dense hydrocarbon fuel
> under such a reconfiguration to reach orbit. So you would be able to
> get a reusable SSTO prototype at a significantly reduced price than
> the $5 billion suggested for the full DC-Y vehicle program.
>
> Bob Clark
>
> Figure 5: X-33 Concept Art from McDonnell Douglas (Frassanito, J.,
> McDonnell Douglas).http://vorlon.case.edu/~jam64/images/SSTO/SSTO_Figure_5.jpg
>
> taken from:
>
> Single Stage to Orbit:
> A Reliable Transport System or an Unattainable Dream?http://vorlon.case.edu/~jam64/work/ssto.htm

Still the development cost of such a DC-X2 would be quite high in the
range
of $450 million (1990's dollars). So I was still thinking about how
small we
could make a scaled up, reconfigured DC-X to achieve orbit to the
extent that
one of the "New Space" companies could afford to build it. I noticed
that on
the DC-X there was a lot of empty space, at least according to the
diagrammatic
image on the Astronautix page:

DC-X.
http://www.astronautix.com/lvs/dcx.htm

I estimated that if we actually fully used up the conical internal
space with
propellant, with just a small area at the top for payload or no
internal
payload bay at all, made it of an all composite construction (remember
the
DC-X was not weight optimized since it would not even go suborbital)
and if
we used highly densified hydrocarbon/LOX propellant, to near the solid
phase,
then we could get quite high velocities from the DC-X, perhaps up to
Mach 20.
In that case only a small scale up from the original DC-X dimensions
would
allow you to reach full orbital performance. This would be much
cheaper than
the DC-X2. I'm thinking it might even doable for less than $100
million in
current dollars.
Then this could be doable by one of the New Space companies,
particularly
those with deep pockets such as SpaceX, Scaled Composites, XCor, Blue
Origin, etc.
The case of Blue Origin is particularly interesting because several of
the
DC-X engineers moved over to work for Blue Origin and the design of
its "New
Shepard" suborbital craft has been likened to that of the DC-X. Blue
Origin's
head Jeff Bezos has also said his intention is to move to orbital
craft:

Blue Origin.
http://en.wikipedia.org/wiki/Blue_Origin

Blue Origin New Shepard.
http://en.wikipedia.org/wiki/Blue_Origin_New_Shepard

Bob Clark

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