Also a GH2-GOX auxiliary power unit running at tank pressure and
hopefully replacing the limited and sometimes troublesome batteries on
the Centaur. Which, since turbines aren't the right answer at that
scale and ULA knew they needed outside talent for this, offers the
ineffable coolness of a high-performance deep space transfer vehicle
running on a flat-six internal combustion engine out of NASCAR
<https://www.roush.com>.
One more reason to lament the lack of sound in space...
John Schilling
john.schilling@xxxxxxxxxxxxxx
(661) 718-0955
On 6/28/2019 7:05 AM, Doug Jones (Redacted sender randome for DMARC) wrote:
Frank Zegler has lead a lot of interesting work on low pressure RCS/ullage thrusters at ULA under the integrated vehicle fluids project. They've demonstrated GH2-GOX motors running at Centaur tank pressure.
https://urldefense.proofpoint.com/v2/url?u=https-3A__forum.nasaspaceflight.com_index.php-3Ftopic-3D37206.160&d=DwICaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=rPTfWqtJdrL0Ber-yr0E_hSjRXuvJH6ZmQx03u8-2as&m=oyeKvE-Ctx7THbIwvpFEy8V9Qi_PwAXdFqkzOjSG1NI&s=Xm5pQ5-eerXNuSNwzL7d3s5aZfQN6nMy2-qP9udRUmw&e=
https://urldefense.proofpoint.com/v2/url?u=https-3A__www.ulalaunch.com_docs_default-2Dsource_extended-2Dduration_integrated-2Dvehicle-2Dpropulsion-2Dand-2Dpower-2Dsystem-2D2011.pdf&d=DwICaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=rPTfWqtJdrL0Ber-yr0E_hSjRXuvJH6ZmQx03u8-2as&m=oyeKvE-Ctx7THbIwvpFEy8V9Qi_PwAXdFqkzOjSG1NI&s=YXKfS5zGfRnKBL8_xSyDppfRB3mScZlu__EOKUWk5Z0&e=
https://urldefense.proofpoint.com/v2/url?u=https-3A__www.ulalaunch.com_docs_default-2Dsource_supporting-2Dtechnologies_space-2Daccess-2Dsociety-2D2012.pdf&d=DwICaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=rPTfWqtJdrL0Ber-yr0E_hSjRXuvJH6ZmQx03u8-2as&m=oyeKvE-Ctx7THbIwvpFEy8V9Qi_PwAXdFqkzOjSG1NI&s=FREtyHVwAizwv3nQBzAodMoGAWiBiwX4sH9P44Udvgw&e=
On 2019-06-27 6:17 PM, Keith Henson wrote:
On Wed, Jun 26, 2019 at 10:07 PM Henry Spencer <hspencer@xxxxxxxxxxxxx> wrote:
On Wed, 26 Jun 2019, Doug Jones wrote:Space junk makes building power satellites in LEO and moving them out
Net Positive Suction Pressure (NPSP) required for most LH2 rocketThe original Centaur had quite low tank pressures, just enough for
engines is in excess of 50 psia. Gossamer tanks are an accident looking
for a time to happen.
structural needs, with boost pumps (driven by peroxide turbines) at the
tank exits to deliver adequate pressure to the engines. But the boost
pumps proved unreliable, and for other reasons the performance demands on
Centaur were relaxed a bit, and they eventually decided to ditch the boost
pumps and accept somewhat higher pressures and thicker tank walls.
to GEO using electric thrusters close to impossible. (They get hit
too many times which is bad, the hits make more debris which is
worse).
The current proposal (credit to Roger Arnold) is to accumulate
15-16,000 tons of power satellite parts and 5000 tons of reaction mass
in LEO then push the stack of parts and reaction mass up with chemical
propulsion via Hohmann transfer orbit to 2000 km. That puts the
construction orbit above almost all the junk. Two of these stacks are
enough for a 32,000-ton power satellite plus the reaction mass needed
to move it out to GEO.
The delta-V for the two impulses is 827 m/s. That translates into a
reaction mass fraction of slightly less than 20% for hydrogen and
slightly more than 20% for methane. This includes enough fuel to get
the tug from 2000 km back to LEO. The exhaust velocity is not so
important when the delta-V you need is small compared to Ve.
If the ground to LEO is Skylon, then hydrogen may be the least
complicated since we can pump out any leftover Skylon hydrogen and
oxygen. Methane may be better if ground to LEO rockets are using it.
Roger makes a case that we can use lightweight, low-pressure engines
and still get the same exhaust velocity since there is no atmosphere.
I don't know much about low-pressure engines.
The reaction mass would be around 20% of 21,000, call it 4200 tons.
The engines and tanks and structure should come in at about 10% of the
reaction mass, roughly estimate the tug at 400 tons.
For the normal ratio of hydrogen to oxygen, the reaction mass would be
3500 tons of LOX and 700 tons of LH2, about 10,000 cubic meters. That
gives a radius of 28.7 for a sphere or a diameter of about 57 m. It
would be subject to around 1/10th of a g and the have to carry the
entire cargo mass.
Does this make sense?
Keith
