Re: More info on Constellation/CEV

From: Alex Terrell (alexterrell_at_yahoo.com)
Date: 01/26/05 

Date: 26 Jan 2005 01:44:03 -0800

Ed Kyle wrote:
> Alex Terrell wrote:
> > Bear in mind it says "less than 20 tons". That gives Boeing an
> > incentive to make it lighter, for their Medium launcher. Weight
will
> no
> > doubt be a critical selection criteria.
> >
> > 20 tons is phenomally heavy - if that's for Spiral 1. Apollo
weighed
> in
> > at under 6 tons,
>
> You're talking about the Command Module only.

I was actually thinking of spiral 1, where the need is space access
only. A Spiral 1 CEV only needs to weigh 6 tons, and could be launched
on Falcon V.

> The Apollo 11 Command/Service Module mass was
> 30.32 metric tons. Apollo 7, a LEO mission,
> had a CSM mass of only 14.8 metric tons because
> it carried much less propellant. The most
> powerful Delta IV-M variant currently available
> would not be able to orbit Apollo 7, but an
> Atlas V with a couple of solids could.

That seems very heavy - how long did it support the crew for?
>
> Clearly much less mass than this is really
> necessary for LEO missions. Soyuz and Shenzhou
> weigh in at 7.5 and 8.4 tons, respectively. A
> straight Delta IV-M could loft them, while the
> smallest Atlas V would be overkill for such a
> mass. But these spacecraft would weigh more
> if configured for an extra-LEO mission. I
> suspect CEV is going to weigh in about the same
> as an Apollo CSM.
>
So 7 tons might be a reasonable target for Spiral 1.

> Shenzhou is the state of the art for launching
> humans into orbit. It weighs more than 8 tons,
> but can only put four people into orbit.
>
> But no matter, putting on a lunar mission means
> figuring out the most efficient way to launch
> lots of propellant.

Agreed that is half the problem. Here's a copy/paste of what I propose
for a Phase 1 Earth - Moon transport system:

TRANSPORT SYSTEM
A lot of the concepts for return to the moon are based on the Apollo
architecture. This makes a lot of sense, as that architecture worked
and was well thought out. However, there is a fundamental difference:
Apollo was about landing, housing, supporting and returning 2 men;
where establishing a lunar base will involve more landings only. The
former is much more complex, as it involved:
§ Landing a launcher, and accommodation, with every landing
§ Having a second vehicle, such as the Command / Service Module
orbiting the moon

Whilst such an architecture might be required for manned landings,
unmanned cargos will be much simpler, involving simply landing a cargo
on the lunar surface.
The following assumes the use of various EELV upgrades. Two launches
are needed to launch into LEO:
1. A 41.7-ton Booster stage. This would consist of a cryogenic rocket
with 38 tons of fuel.
2. The Lunar Module, with a mass of 33.3 tons. This would consist
either of a lunar lander, or a lunar obiter based on the CEV.

The Booster launches the Lunar Module with a delta V of 3,061 m/s,
which puts the Lunar Module into a Lunar transfer Orbit. During
transfer to the moon, the accelerator separates. The Accelerator stage
could impact the moon or remain in Earth Orbit, to burn up in the
Earth's atmosphere.
The Lunar Module will reach the moon after a voyage of approximately 3
days.
UNMANNED LAUNCHES
In this instance the Lunar module is an unmanned, lunar lander. The
additional delta V required for a lunar landing is 3,000 m/s. The
engines are powered by Kerosene and Liquid Oxygen, to avoid the need to
store Liquid Hydrogen during the voyage. The 33.33 ton module contains
20 tons of fuel and a 10 tons of cargo.

MANNED LAUNCHES
Manned launches are broken down into two components.
1. The Crew Exploration Vehicle, which transports four astronauts to
lunar orbit and returns them to Earth. .
2. A lander, which transports the astronauts from lunar orbit to the
lunar base, and includes an ascender stage.
The CEV is placed in orbit as part of the Lunar Module. With a Delta-V
requirement of some 1,000 m/s, the CEV can mass 24 tons in lunar orbit.
This is less than the 30 tons of the Apollo CSM in lunar orbit. The CEV
will have a larger crew capacity (4-8) than Apollo (3), but additional
further weight savings will be achieved:
§ The CSM needed to maintain astronauts for up to 12 days. The CEV
will spend only the minimum time in lunar orbit, so seven days will be
the requirement.
§ The CSM used storable propellants with a lower ISP than oxygen /
kerosene
§ Further weight savings can be introduced by using more advanced
materials and electronics

The ascender stage needs to transport a crew of 4 from the lunar
surface to lunar orbit, where the crew will transfer to the CEV. As
this takes a few hours at most, the ascender stage needs no life
support equipment and can even be unpressurised. The ascender stage,
with four crew, can therefore mass about 1.5 tons unfuelled. As the
ascender stage may need to remain on the lunar surface some time, it
would need to use storable propellants. Assuming an exhaust velocity of
3,000 m/s (Isp = 306 m/s), and a delta V requirement of 2,200 m/s, 1.5
tons of fuel will be needed. This makes the minimum lunar launch mass 3
tons.

This compares with the Apollo LM ascent stage mass of 4.54 tons.
However, this contained the life support and space for the crew to
remain on the lunar surface for about week, and was a pressurised
structure.
To land the 3 tons ascender stage on the lunar surface, there are a two
options.
1. Land it as part of a standard, 10-ton pallet, along with seven tons
of additional cargo. This could be the supplies that the crew of four
would need for their stay on the surface. This approach would require
two missions to be launched within a short timeframe, but would also
enable a useful combination of personnel and supplies to be delivered.
2. Create a smaller mission in parallel to the CEV orbit mission, just
to transport the lander/ascender to the lunar surface. As this needs to
land some 3-4 tons on the lunar surface, this could be launched with a
single mission with an LEO capability of 22 to 30 tons.

The exact combination should be chosen based on tenders provided by
competing launch companies.

Relevant Pages

  • Re: Next X
    ... lunar transfer speed. ... Indonesia respectively - for a more normal equatorial orbit. ... 910 sec Isp - laser thermal stage ... A 3000 metric ton vehicle -launches 490 tons into LEO. ...
    (sci.space.policy)
  • Re: Establish demand
    ... the total number of launches, almost 120, and pretending that each ... mission delivered 30 tons to orbit, the cost per pound would be over ... falcon 9 series or a delta IV, that made deliveries for $4000/Kg, but ... Since demonstrably we do not yet have RLV technology, the rational approach indicated that we should first attempt less ambitious variations of existing ELV techniques, for instance, recovery of the first stages, demonstration of cryogenic expendable single stage to orbit, etc. ...
    (sci.space.policy)
  • Re: Next X
    ... lunar transfer speed. ... Indonesia respectively - for a more normal equatorial orbit. ... 910 sec Isp - laser thermal stage ... A 3000 metric ton vehicle -launches 490 tons into LEO. ...
    (sci.space.policy)
  • Re: Establish demand
    ... the total number of launches, almost 120, and pretending that each ... mission delivered 30 tons to orbit, the cost per pound would be over ... falcon 9 series or a delta IV, that made deliveries for $4000/Kg, but ... Since demonstrably we do not yet have RLV technology, the rational approach indicated that we should first attempt less ambitious variations of existing ELV techniques, for instance, recovery of the first stages, demonstration of cryogenic expendable single stage to orbit, etc. ...
    (sci.space.policy)
  • Re: Nuclear rockets.
    ... moon, but instead to the moon's L1 (roughly 58,000 km above the lunar ...  In fact you don't need 256,000 tons - something like ... Guth Tether Plan: 256,000 tons distributed between L1 and lunar ...
    (sci.space.policy)
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