another capsule concept

The latest issue of JBIS (Nov/Dec 2005) leads off with a paper on
multi-role capsules by Mark Hempsell, who was one of the leaders of the
BAe MRC study in the late 1980s. After some general discussion of goals
and design alternatives, it presents his latest design, "Excalibur". I
have minor complaints about it -- I think he's being too optimistic on a
few details -- but it's very interesting...

It's a semiballistic capsule, a vaguely Apollo shape but with a somewhat
elliptical base, to achieve a higher angle of attack (45deg) and hence
better reentry L/D (circa 0.7), which means a LEO reentry never exceeds
1.5G and a crossrange of several hundred kilometers is available. The
base is 5.6x4.5m, reasonably compatible with today's large launchers like
Ariane 5 and the EELVs. On the leeward side here's a bit of a "back
porch" sticking out, see below. On the apex is an ISS-compatible APDS
docking system, protected during ascent and reentry by a hinged cap (the
inside of which also houses some in-space-only hardware like a high-gain
antenna).

It's fully reusable, the only expendable component being the ablative base
heatshield. No service module, no escape tower, no jettisoned bits.

It has its own internal OMS system, which doubles as launch-escape
propulsion and also does DC-X-style rocket landings -- eliminating the
need for parachutes, providing gentle land touchdown, and permitting
landing on airless bodies. Moreover, it has about 2km/s of delta-V,
because just over half its launch mass is fuel. If you add an expendable
drop-tank set, it can go from lunar orbit to the surface and back to
orbit, or from the Martian surface to orbit.

The engines burn N2O4 and hydrazine (ick), as do the primary RCS
thrusters. The two fluids are also (separately) decomposed, producing
nitrogen, hydrogen, and oxygen; the hydrogen and oxygen are used by fuel
cells to produce power (and drinking water), the oxygen and a bit of the
nitrogen are used for life support, and the nitrogen is used for a
cold-gas secondary RCS system for maneuvering in contamination-sensitive
environments.

The cabin normally holds four for a 10-day flight, although a fifth can be
accommodated prone for medical evacuation. The "back porch" is the
protruding end of a small airlock, including suit stowage. Crew and their
equipment can be traded off for modest amounts of cargo.

Finally, fully fueled it weighs 10.1t, meaning that an Ariane 5 or an
all-liquid single-core Atlas V could launch it to ISS. To do the same
with Delta IV you'd have to offload some fuel, but there'd still be lots
for a station visit.

The contrast to NASA's Continued Employment Vehicle is rather striking.
--
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I like the way you are thiking!
Any chance of getting any specs for this capsule?

On Mon, 31 Oct 2005 22:11:29 +0100, Henry Spencer
wrote:

The latest issue of JBIS (Nov/Dec 2005) leads off with a paper on
multi-role capsules by Mark Hempsell, who was one of the leaders of the
BAe MRC study in the late 1980s. After some general discussion of goals
and design alternatives, it presents his latest design, "Excalibur". I
have minor complaints about it -- I think he's being too optimistic on a
few details -- but it's very interesting...

It's a semiballistic capsule, a vaguely Apollo shape but with a somewhat
elliptical base, to achieve a higher angle of attack (45deg) and hence
better reentry L/D (circa 0.7), which means a LEO reentry never exceeds
1.5G and a crossrange of several hundred kilometers is available. The
base is 5.6x4.5m, reasonably compatible with today's large launchers like
Ariane 5 and the EELVs. On the leeward side here's a bit of a "back
porch" sticking out, see below. On the apex is an ISS-compatible APDS
docking system, protected during ascent and reentry by a hinged cap (the
inside of which also houses some in-space-only hardware like a high-gain
antenna).

It's fully reusable, the only expendable component being the ablative
base
heatshield. No service module, no escape tower, no jettisoned bits.

It has its own internal OMS system, which doubles as launch-escape
propulsion and also does DC-X-style rocket landings -- eliminating the
need for parachutes, providing gentle land touchdown, and permitting
landing on airless bodies. Moreover, it has about 2km/s of delta-V,
because just over half its launch mass is fuel. If you add an expendable
drop-tank set, it can go from lunar orbit to the surface and back to
orbit, or from the Martian surface to orbit.

The engines burn N2O4 and hydrazine (ick), as do the primary RCS
thrusters. The two fluids are also (separately) decomposed, producing
nitrogen, hydrogen, and oxygen; the hydrogen and oxygen are used by fuel
cells to produce power (and drinking water), the oxygen and a bit of the
nitrogen are used for life support, and the nitrogen is used for a
cold-gas secondary RCS system for maneuvering in contamination-sensitive
environments.

The cabin normally holds four for a 10-day flight, although a fifth can
be
accommodated prone for medical evacuation. The "back porch" is the
protruding end of a small airlock, including suit stowage. Crew and
their
equipment can be traded off for modest amounts of cargo.

Finally, fully fueled it weighs 10.1t, meaning that an Ariane 5 or an
all-liquid single-core Atlas V could launch it to ISS. To do the same
with Delta IV you'd have to offload some fuel, but there'd still be lots
for a station visit.

The contrast to NASA's Continued Employment Vehicle is rather striking.



--
Using Opera's revolutionary e-mail client: http://www.opera.com/mail/

Henry Spencer wrote:
The latest issue of JBIS (Nov/Dec 2005) leads off with a paper on
multi-role capsules by Mark Hempsell, who was one of the leaders of the
BAe MRC study in the late 1980s. After some general discussion of goals
and design alternatives, it presents his latest design, "Excalibur". I
have minor complaints about it -- I think he's being too optimistic on a
few details -- but it's very interesting...

This appears to be available - not for free though - he

http://www.aiaa.org/content.cfm?page...aper&gID=42775

Selling $5 pdf files with a $10 handling fee is a bit odd though, surely
they should be able to get a more efficent card handler?


The engines burn N2O4 and hydrazine (ick), as do the primary RCS
thrusters. The two fluids are also (separately) decomposed, producing
nitrogen, hydrogen, and oxygen; the hydrogen and oxygen are used by fuel
cells to produce power (and drinking water), the oxygen and a bit of the
nitrogen are used for life support, and the nitrogen is used for a
cold-gas secondary RCS system for maneuvering in contamination-sensitive
environments.

The impression I got from reading the paper was that such total
integration was delibrate and that the propellant choice was probably
heavily affected by this. Also, this way longer missions requiring more
fuel also automaticly have a larger supply of oxygen and water.


Finally, fully fueled it weighs 10.1t, meaning that an Ariane 5 or an
all-liquid single-core Atlas V could launch it to ISS. To do the same
with Delta IV you'd have to offload some fuel, but there'd still be lots
for a station visit.

The contrast to NASA's Continued Employment Vehicle is rather striking.

For one thing, its a design for just the capsule, ready to be launched
on whatever carrier comes along. The other nifty thing is that with the
drop tanks, something that can be launched with a similar vehicle you
essentially get a lunar mission for four. Ok, not quite - but rather
close, even if you would need (according to my very quick and dirty
calculation) Ariane 5 ECB instead of ECA.

--
Sander

+++ Out of cheese error +++

John Thingstad wrote:
I like the way you are thiking!
Any chance of getting any specs for this capsule?


dry weight: 5000 kg
propellant: 5100 kg
engine: N2H4 + N2O4 biprop
Thrust (vac): 31.8kN per engine
Num(engines): 4

--
Sander

+++ Out of cheese error +++

Interesting concept.

I don't like the propellant choice and the complex shape, but using the
OMS thrusters for safe abort and landing is a very good idea. It is a
shame that nasa does not even consider powered vertical landing. As far
as I know, none of the studies done a year ago used powered vertical
landing.

Talented amateurs like Armadillo Aerospace can manage powered landing
on a shoestring budget, yet nasa still thinks it is too complex. And
besides, since the safe abort system is a critical system that has to
work reliably, you might as well use it for OMS and landing.

The contrast to NASA's Continued Employment Vehicle is rather striking.

Heh. This is the best explanation for the CEV acronym I saw yet.

"Sander Vesik" wrote in message
...
Henry Spencer wrote:
The latest issue of JBIS (Nov/Dec 2005) leads off with a paper on
multi-role capsules by Mark Hempsell, who was one of the leaders of the
BAe MRC study in the late 1980s. After some general discussion of goals
and design alternatives, it presents his latest design, "Excalibur". I
have minor complaints about it -- I think he's being too optimistic on a
few details -- but it's very interesting...

This appears to be available - not for free though - he

http://www.aiaa.org/content.cfm?page...aper&gID=42775

Selling $5 pdf files with a $10 handling fee is a bit odd though, surely
they should be able to get a more efficent card handler?

For those of us that don't want to pay $15 for a PDF, check your local
library for JBIS. I know the public library near me carries it. It's also
likely to be found in many university libraries (especially science and
engineering colleges).

Jeff
--
Remove icky phrase from email address to get a valid address.

In article , Henry Spencer says...

The latest issue of JBIS (Nov/Dec 2005) leads off with a paper on
multi-role capsules by Mark Hempsell, who was one of the leaders of the
BAe MRC study in the late 1980s. After some general discussion of goals
and design alternatives, it presents his latest design, "Excalibur". I
have minor complaints about it -- I think he's being too optimistic on a
few details -- but it's very interesting...

Indeed, and it's somewhat similar to ideas I've been kicking around.
Now I'm going to have to find a copy of the latest JBIS, and the only
library I know has it is about eighty miles away. Thanks, Henry :-)


It's a semiballistic capsule, a vaguely Apollo shape but with a somewhat
elliptical base, to achieve a higher angle of attack (45deg) and hence
better reentry L/D (circa 0.7), which means a LEO reentry never exceeds
1.5G and a crossrange of several hundred kilometers is available. The
base is 5.6x4.5m, reasonably compatible with today's large launchers like
Ariane 5 and the EELVs. On the leeward side here's a bit of a "back
porch" sticking out, see below.

The only problem here is that the 5.6-meter part means it won't either
fit inside or duplicate the form factor of any existing *fairing*, and
so you'll have to requalify the launcher with the new aerodynamics. New
and, from the sound of it, asymmetric.

One of the ideas I've been playing with, is to almost duplicate the
Atlas EPF in size, shape, and interface, to make the capsule a drop-in
replacement on an Atlas 400 series.


On the apex is an ISS-compatible APDS docking system, protected during
ascent and reentry by a hinged cap (the inside of which also houses some
in-space-only hardware like a high-gain antenna).

It's fully reusable, the only expendable component being the ablative base
heatshield. No service module, no escape tower, no jettisoned bits.

No sense doing it any other way, IMO. Unless you're *really* dead-set on
duplicating Apollo, that is, in which case you have to expect the part
with the premature cancellation and the long hiatus in manned spaceflight.


It has its own internal OMS system, which doubles as launch-escape
propulsion and also does DC-X-style rocket landings -- eliminating the
need for parachutes, providing gentle land touchdown, and permitting
landing on airless bodies.

The rocket landing I like, but I'm skeptical about the launch-escape
part. There's enough delta-V in the system, sure, but that mission
also calls for raw thrust and rapid response at levels one normally
associates with solid rockets.


Moreover, it has about 2km/s of delta-V, because just over half its
launch mass is fuel. If you add an expendable drop-tank set, it can
go from lunar orbit to the surface and back to orbit, or from the
Martian surface to orbit.

I assume it can also go from Mars orbit to surface, albeit not the
full orbit-surface-orbit mission unless you refuel on-site. Which
is problematic, because...


The engines burn N2O4 and hydrazine (ick), as do the primary RCS
thrusters. The two fluids are also (separately) decomposed, producing
nitrogen, hydrogen, and oxygen; the hydrogen and oxygen are used by fuel
cells to produce power (and drinking water), the oxygen and a bit of the
nitrogen are used for life support, and the nitrogen is used for a
cold-gas secondary RCS system for maneuvering in contamination-sensitive
environments.

....those really are atrocious propellants. I like the tight integration,
but really, most any fuel/oxidizer combination can give you oxygen, water,
cold gas and electricity. Pick something that won't kill your astronauts
if they get a faint whiff of it, and bonus points for picking something
you can produce on the Moon and/or Mars.


The cabin normally holds four for a 10-day flight, although a fifth can be
accommodated prone for medical evacuation. The "back porch" is the
protruding end of a small airlock, including suit stowage. Crew and their
equipment can be traded off for modest amounts of cargo.

I'd prefer to use the forward docking hatch as the airlock, to preserve
aerodynamic symmetry for ascent.


Finally, fully fueled it weighs 10.1t, meaning that an Ariane 5 or an
all-liquid single-core Atlas V could launch it to ISS. To do the same
with Delta IV you'd have to offload some fuel, but there'd still be lots
for a station visit.

This, almost blows my suspension of disbelief. I don't think you can
fit that much functionality into five tons of dry mass. I've pretty
much accepted ten tons dry for this sort of multifunctional vehicle,
which means you can make LEO (including ISS) from a bare EELV, but
need to refuel on-orbit for any high-DV mission.


The contrast to NASA's Continued Employment Vehicle is rather striking.

Indeed it is. And it's not a work of extraordinary genius, either. Any
reasonably clever person skilled in the field can figure out how to save
NASA the cost of eight thousand or so technicians, engineers, and managers.


--
*John Schilling * "Anything worth doing, *
*Member:AIAA,NRA,ACLU,SAS,LP * is worth doing for money" *
*Chief Scientist & General Partner * -13th Rule of Acquisition *
*White Elephant Research, LLC * "There is no substitute *
* for success" *
*661-951-9107 or 661-275-6795 * -58th Rule of Acquisition *

In article ,
John Schilling wrote:
Now I'm going to have to find a copy of the latest JBIS, and the only
library I know has it is about eighty miles away. Thanks, Henry :-)

Always happy to be of service. :-)

The only problem here is that the 5.6-meter part means it won't either
fit inside or duplicate the form factor of any existing *fairing*...

Unless you launch it *tilted* underneath a fairing. (He does note that it
will fit, tilted, in the shuttle cargo bay, which means it'll fit in a 5m
fairing the same way.) But that doesn't seem to be what he has in mind;
the hinged apex cap does point to exposed launch.

so you'll have to requalify the launcher with the new aerodynamics. New
and, from the sound of it, asymmetric.

The "back porch" does introduce a bit of asymmetry, but as I recall (the
issue isn't handy at the moment) it wasn't large. Agreed, though, that it
would take some aerodynamic requalification.

The rocket landing I like, but I'm skeptical about the launch-escape
part. There's enough delta-V in the system, sure, but that mission
also calls for raw thrust and rapid response at levels one normally
associates with solid rockets.

He doesn't discuss his assumptions about launch-escape requirements.
Certainly you can use the OMS for some kinds of escape maneuvers, but it
can't do everything that a traditional escape tower can. The question
that needs hard thought is how necessary the traditional requirements are.
One or two of them simply go away -- with no parachutes, altitude and
distance requirements for a pad abort can be relaxed -- and you might
deem others overly severe in hindsight.

Remember that traditional escape requirements basically derive from those
of Mercury, which was to go up on a launcher that was then infamous for
gross unreliability, far worse than today's (mature) launchers. Perhaps a
thoughtful reassessment (an honest one, with the press releases written
afterward rather than beforehand) would find some of those requirements
excessive.

I note with interest that Gemini did not have full-envelope escape -- at
the more extreme speeds and altitudes, the procedure was to stay with the
capsule for a while -- that the MOL Gemini would have used its retros for
escape, and that Caldwell Johnson thought Apollo did not really need an
escape tower.

...those really are atrocious propellants.

Agreed. It's one of the things about his scheme that I definitely don't
like. It also, if I'm interpreting his cutaway drawing correctly, gives
him a rather odd-shaped pressure hull, because two big spherical tanks
take chunks out of his internal volume.

I'd prefer to use the forward docking hatch as the airlock, to preserve
aerodynamic symmetry for ascent.

But then you can't do spacewalks while docked, the spacewalk hatch is
limited to what will fit inside the docking ring, and you've got an
awkward hatch-access problem for use on planetary surfaces.

He doesn't discuss how he evaluated the tradeoffs on this one. If only
for safety, though, I think you end up with a side hatch of some kind in
addition to the forward one, and then you might as well put the airlock
behind the side hatch. You can do that without his protruding back porch,
although at some cost in internal volume.

This, almost blows my suspension of disbelief. I don't think you can
fit that much functionality into five tons of dry mass...

I think he's making some optimistic assumptions about what he can do with
modern materials and electronics and his unified fluid system. I haven't
scrutinized his mass budget carefully (and in any case it is not too
detailed).

However, 10t dry is 2.5t/person. Considering that we can give each guy
his own Mercury capsule for 1.5t/person, that seems excessive.
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"Henry Spencer" wrote in message
...
The latest issue of JBIS (Nov/Dec 2005) leads off with a paper on
multi-role capsules by Mark Hempsell, who was one of the leaders of the
BAe MRC study in the late 1980s. After some general discussion of goals
and design alternatives, it presents his latest design, "Excalibur". I
have minor complaints about it -- I think he's being too optimistic on a
few details -- but it's very interesting...

I saw Mr. Hempsell present a paper on this concept (or its immediate
predecessor) at the 2004 IAF conference in Vancouver, and chatted with him
afterwards. I agree that there are some things that seem a little
optimistic, and manned vehicle design is complex enough that I'm cautious
about any project that's essentially a one-man show (or in this case, Mr.
Hempsell plus his students, I believe - he's a professor these days).
However, it was a pleasure to meet the guy who lead the MRC team. Whether
his designs are valid or not, I think he serves an important role by
reminding people that just because "the physics haven't changed" doesn't
mean the designs shouldn't, and that modern capsules could be quite
different from the old ones.

The engines burn N2O4 and hydrazine (ick), as do the primary RCS
thrusters. The two fluids are also (separately) decomposed, producing
nitrogen, hydrogen, and oxygen; the hydrogen and oxygen are used by fuel
cells to produce power (and drinking water), the oxygen and a bit of the
nitrogen are used for life support, and the nitrogen is used for a
cold-gas secondary RCS system for maneuvering in contamination-sensitive
environments.

Mr. Hempsell pointed me to an earlier paper on this specific subsystem from
the 1993 IAF conference, which may be of interest to some here. It goes into
greater detail.

C. M. Hempsell "Extracting Power and ECLSS Consumables From Spacecraft
Propulsion Systems." IAF-93-S.1.460.

According to the paper, the initial concept was actually developed as part
of the MRC study at BAE but not disclosed at the time. The first thing I'd
worry about is trace contaminants in the air supply, since it's made from
decomposed and filtered N2O4. You also have to trade off the benefits of
highly integrated systems vs the risk that a single failure will take down
everything - power, propulsion, life support etc. However, it's an
interesting idea for at least two reasons. One is that, despite the hazards,
the aerospace industry does know how to handle hydrazine/N2O4 and there are
a lot of off-the shelf components, systems, and procedures for it. The other
is that it can provide nitrogen, which can be a significant fraction of the
atmosphere supply requirement. Nitrogen is not readily produced by other
proposed integrated commodity systems which run on hydrocarbons or
hydrogen/oxygen.

Josh Hopkins

In article ,
Josh Hopkins wrote:
...The first thing I'd worry about is trace contaminants in the air
supply, since it's made from decomposed and filtered N2O4...

Yes, whatever contaminant-catching systems sit in between the N2O4
decomposer and the cabin air are clearly in the "this just has to work
really well all the time" category.

...it can provide nitrogen, which can be a significant fraction of the
atmosphere supply requirement...

Although you lose nitrogen mostly by air leakage... and I note an
interesting McDonnell-Douglas paper in the Jan 1972 JS&R, arguing that the
historically high leak rates of manned spacecraft are the result of lack
of attention to the issue rather than anything inherent. (Wide variation
in leak rate from craft to craft indicates that whatever factors cause it
are not under control... and the Skylab MDA, designed with an explicit
goal of low leakage, had a leak rate orders of magnitude lower than Gemini
or Apollo.)

Nitrogen is not readily produced by other proposed integrated commodity
systems which run on hydrocarbons or hydrogen/oxygen.

Although an N2O system could provide it -- not entirely free from the
trace-contaminants issue, but much more benign than N2O4 -- and there has
been some interest in N2O for low-toxicity RCS systems.
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