CEV development cost rumbles

On or about Tue, 09 Mar 2004 17:22:29 GMT, Bruce Sterling Woodcock made the sensational claim that:
And I contend that:

1. Stand alone repair will not be implemented.

So then what happens if you have an abort to orbit and are unable to reach
ISS? Just because it's an ISS flight doesn't guarantee the orbiter will get
there. I'll even stick my neck out and say that'll be exactly the situation
we'll find ourselves in one day. I don't think it'll be another Columbia
type situation, but if I had to bet on the next major failure I'd think SSMEs.
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With the need to provide increased bandwidth between processors, more
powerful local processors, more connections [...] to control elements...

A transputer had enough local processing capability (and, in some cases,
memory) as well as sufficient comms capability for any control application
I can imagine. All in one small package - only a crystal, one capacitor
and some RS422 drivers required.

Jan

LooseChanj wrote:
On or about Tue, 09 Mar 2004 17:22:29 GMT, Bruce Sterling Woodcock made the sensational claim that:

And I contend that:

1. Stand alone repair will not be implemented.


So then what happens if you have an abort to orbit and are unable to reach
ISS?

That's multiple failures. Not impossible, but typically you don't try
to address them.

Brett

1. Stand alone repair will not be implemented.

So then what happens if you have an abort to orbit and are unable to reach
ISS?

But then you are already in a double failure scenario. For an HST flight,
that would not be the case. As long as we assume that the failure to reach
the designated orbit and any TPS damage are uncorrelated - which probably
is not that far from the truth - this makes for a significant distinction
between the two cases.

Jan

So then what happens if you have an abort to orbit and are unable to reach
ISS?

Welll\ we really need a fast way to get emergency supplies not only to a
stranded orbiter but ISS itself.

If you ask me the lack of this capability will be the next major nasa screw up.

(Hallerb) writes:

So then what happens if you have an abort to orbit and are unable to reach
ISS?

Welll\ we really need a fast way to get emergency supplies not only to a
stranded orbiter but ISS itself.

If you ask me the lack of this capability will be the next major nasa screw up.

If the shuttle is going to ISS, but can't quite make it, shouldn't it
be in an orbit that Soyuz or Progress could reach? There is also the
"care package launched on an expendable" that Jim O. has mentioned in
the past. It seems reasonable to create the frame for the "care
package", so you'd have it ready to load and launch on whatever ELV is
nearest to launch.

Jeff
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Allen Thomson wrote:
No argument. I was thinking of a bunch of Z80s monitoring joints,
pressures, temperatures, gas composition, vibration, etc., etc.
throughout the ship. They'd initiate local action and/or report
up the line to the higher-level processors or even the crew.

The space station is set out in a 3tier hiearchical architecture. (Well,
actuallly it is 5 tiered.)


0 User laptop for user interface (not considered a tier)
1 Control tier (only one MDM active) which provides vehicle level control/overseeing.
2 Local (system specific software, and data gathering).
3 User (controls the data buses to the devices below).
4 Sensor/switch/device (not considered a tier)

So, if you have 5000 devices and sensors, they are not all controlled by one
computer. This means that each MDM's processing requirements are limited.

There is one active Tier 1 computer (1 warm backup, one backup powered off)
There are 5 active tier 2 computers (4 backups powered off, and one warm
backup for GNC)
There are 12 Tier 3 computers, no backups.

Tier 2 computers collect the data from tier 3 computers, do some processing
(for instance, calculate gimbal angles for GNC software) and make that data
available to Tier 1 on request.

Tier 1 is the big logic thing, the "great" overseer, and is also in charge of
comms with MCC and russian segment. Tier 2 is more of an autonomic layer that
does raw processing and keeping of data.

So, as you go down, each tier has simpler an simpler software. Tier 1 has the
complex station management software. Tier 3 is just a bus controller.

Temperature sensors don't need their own "CPU". They can use a simpler chip to
transmit the values on the bus when polled to do so. Tier3 then makes the
value available to Tier 2 which in turn makes it available to Tier 1. Tier 1
only talks to tied 2. And the laptops only talk to tier 1.

None of this is fault tolerant. Failure of the Tier 1 MDM requires manual
activation of the warm backup, (and then powering on the cold backup so it
becomes the warm backup).

Now, if this were left to private enterprise that has no ties to the military,
the architecture would probably look very different/simpler in exchange for
using fault tolerant hardware. On the other hand, if you require hardened
hardware, and your only source is military devices/systems, then you may be
forced to use similar architecture.

There is a major/huge difference between a space station and a launch vehicle.
Like a cruise ship, if a space station computer fails, the station continues
to safely orbit, and crew life is not immediatly endangered (it happened on
Mir, and to a much lesser extent on Alpha also)

But on a launch vehicle, you cannot afford to miss a beat between launch and
final orbit insertion. You need not only consider failure of computers, but
also failure of a device/actuator. So you also need redundant devices.

"LooseChanj" wrote in message
om...
On or about Tue, 09 Mar 2004 17:22:29 GMT, Bruce Sterling Woodcock
made the sensational claim that:
And I contend that:

1. Stand alone repair will not be implemented.

So then what happens if you have an abort to orbit and are unable to reach
ISS?

They'll wing it.

Bruce

One notable example is emergency crew return from ISS. Winged
vehicles had been NASA's preference for this role for many years,
despite the fact that the only vehicle now performing this role is a
capsule.


It all depends on how you define the role of the CRV. Remember that this isn't
like an enterprise shuttlecraft that can land anywhere in a couple of minutes,
no matter what the enterprise's orbit is.

There are many levels of emergency:
A- station failure and no longer usable. There is no "emergency" to land, you
can stay on the soyuz until it is aligned with the landing area, which should
happen in less than 24 hours.

B-crew illness. This one is the politically difficult one. Do you need to be
in a hospital within 30 minutes, or do you need to be in a hospital within 24
hours ? Do you accept the reality that in case of medical emergency, you may
have a better chance with performing the surgery on the ISS with doctors on
ground supervising ?

C-solar/space event (meteor shower, extreme solar flare etc). This would
probably require immediate de-orbit to get under the atmosphere's protection
ASAP and worry about being rescued later. But it it does require a vehicle
that could land anywhere because you wouldn't have time to wait until you're
aligned to some landing target.

Soyuz performs A and C extremely well. Doesn't do too well on B because it
needs to target landing far enough from civilisation, yet close enough to be
rescued.

Seems to me that for an escape pod, a capsule does the job. Its role is to
save lives, not bring people and gear back to some cushy airport with mobile
lounges. The one issue that clouds the capsule is re-entry G forces and
whether that would be a show stopper if you have a sick crewmember.

A winged vehicle is also more limited with regards to landing site weather
than a capsule. With the capsule, you could wait a few extra minutes and land
a couple hundred km further and be away from that bad weather. (but you may
then be out of range of helicopters for rescue).

John Doe writes:
One notable example is emergency crew return from ISS. Winged
vehicles had been NASA's preference for this role for many years,
despite the fact that the only vehicle now performing this role is a
capsule.

B-crew illness. This one is the politically difficult one. Do you need to be
in a hospital within 30 minutes, or do you need to be in a hospital within 24
hours ? Do you accept the reality that in case of medical emergency, you may
have a better chance with performing the surgery on the ISS with doctors on
ground supervising ?

Soyuz performs A and C extremely well. Doesn't do too well on B because it
needs to target landing far enough from civilisation, yet close enough to be
rescued.

This has been discussed in the past. Comparing planned evacuation of
someone sick or injured off ISS and off the base at the South Pole (in
the dead of winter) proves interesting. It's not like you can be
evacuated in a matter of hours from the South Pole, yet it is a
permanent base with many people on it, many of them researchers.

Extending this to space... If we're willing to accept the risk of
sending people to the Moon and Mars (days and months away), then why
in the world do we need to get back from LEO in a minutes? If we
can't accept that risk in LEO, how can we accept that risk on Mars?

Even better, why not develop ways to deal with medical emergencies in
LEO (and on the Moon and Mars), rather than "running home to Mommy to
treat every cut and scrape".

Jeff
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