MESSENGER Launch Rescheduled

Personally I would rather they delay the launch a year and get a higher
power launch vehicle to deliver it sooner than currently planned. In the
old days NASA managed to get probes to the planets quickly, these days we
seem to always be doing half a dozen flyby's for cheap gravity assists
instead of just burning more fuel at the launch.

"rk" wrote in message
...
http://messenger.jhuapl.edu/news_roo..._03_24_04.html

MESSENGER Launch Rescheduled

The planned May launch of NASA's MESSENGER spacecraft - the first designed
to
orbit the planet Mercury *- has been rescheduled for no earlier than July
30.

The new launch period, a backup to the May plan, extends from July
30-August
13, 2004. Several factors led to NASA's decision to move the launch from
its
original date, including a desire to perform more testing of MESSENGER's
fault-protection system software. This allows the spacecraft to check its
own
health and, when necessary, switch between alternative backup systems.
This
will also create some additional time for the test team to complete final
assembly and checkout, affording a more comfortable spacecraft processing
schedule.

-end excerpt-

--
rk, Just an OldEngineer
"For a successful technology, reality must take precedence over public
relations, for nature cannot be fooled."
-- R. Feynman, Appendix F.

"Allen W. McDonnell" wrote in message
...
Personally I would rather they delay the launch a year and get a higher
power launch vehicle to deliver it sooner than currently planned. In the
old days NASA managed to get probes to the planets quickly, these days we
seem to always be doing half a dozen flyby's for cheap gravity assists
instead of just burning more fuel at the launch.

Even if it means the mission never gets funded?

And I think you overestimate exactly how quickly NASA got probes to planets.

For one thing, we've never had an orbiter of Mercury. That takes a lot of
work.

"Greg D. Moore \(Strider\)" wrote in
:


"Allen W. McDonnell" wrote in message
...
Personally I would rather they delay the launch a year and get a
higher power launch vehicle to deliver it sooner than currently
planned. In the old days NASA managed to get probes to the planets
quickly, these days we seem to always be doing half a dozen flyby's
for cheap gravity assists instead of just burning more fuel at the
launch.

Even if it means the mission never gets funded?

And I think you overestimate exactly how quickly NASA got probes to
planets.

For one thing, we've never had an orbiter of Mercury. That takes a
lot of work.

And the only other probe we've ever sent to Mercury, Mariner 10, had to do
a Venus flyby to get there, even back in the days when NASA used bigger
rockets.


--
JRF

Reply-to address spam-proofed - to reply by E-mail,
check "Organization" (I am not assimilated) and
think one step ahead of IBM.

"Greg D. Moore (Strider)" wrote in message
...

"Allen W. McDonnell" wrote in message
...
Personally I would rather they delay the launch a year and get a higher
power launch vehicle to deliver it sooner than currently planned. In
the
old days NASA managed to get probes to the planets quickly, these days
we
seem to always be doing half a dozen flyby's for cheap gravity assists
instead of just burning more fuel at the launch.

Even if it means the mission never gets funded?

And I think you overestimate exactly how quickly NASA got probes to
planets.

For one thing, we've never had an orbiter of Mercury. That takes a lot of
work.


Why should mariner 10 in 1973 require 1 Venus flyby to set up 3 Mercury
flyby's and the 2004 Messenger mission require one Earth flyby, 2 Venus
flyby's and 3 Mercury flyby's before it actually goes into orbit in 2011?
Getting to Mercury is less energy intensive than getting to Jupiter. Using
'energy saver' orbits is fine so long as you have all the time in the world,
but NASA has developed the IMO bad habit of selecting the cheapest orbits no
matter what the time delay. To get people to vote and fund space missions
you have to give them pretty pictures to look at. Maybe NASA is smarter
than I think because the way they are doing Messenger they will get a nice
set of Earth pics and two sets of Venus pics to publish, but Venus and Earth
are somewhat well known. Mercury is mostly still unknown territory so I
want the mission to get there and start Mercury science while I am still
alive and interested, not 7 years down the road when many things may have
changed in both my life and the world at large.

Allen W.

"Allen W. McDonnell" wrote in message
...

"Greg D. Moore (Strider)" wrote in
message
...

"Allen W. McDonnell" wrote in message
...
Personally I would rather they delay the launch a year and get a
higher
power launch vehicle to deliver it sooner than currently planned. In
the
old days NASA managed to get probes to the planets quickly, these days
we
seem to always be doing half a dozen flyby's for cheap gravity assists
instead of just burning more fuel at the launch.

Even if it means the mission never gets funded?

And I think you overestimate exactly how quickly NASA got probes to
planets.

For one thing, we've never had an orbiter of Mercury. That takes a lot
of
work.


Why should mariner 10 in 1973 require 1 Venus flyby to set up 3 Mercury
flyby's and the 2004 Messenger mission require one Earth flyby, 2 Venus
flyby's and 3 Mercury flyby's before it actually goes into orbit in 2011?
Getting to Mercury is less energy intensive than getting to Jupiter.

Are you sure about that? I thought it was more intensive, since you
effectively have to lose all your momentum.

And going into orbit about a body is also more intensive then doing a flyby.


Using
'energy saver' orbits is fine so long as you have all the time in the
world,
but NASA has developed the IMO bad habit of selecting the cheapest orbits
no
matter what the time delay. To get people to vote and fund space missions
you have to give them pretty pictures to look at. Maybe NASA is smarter
than I think because the way they are doing Messenger they will get a nice
set of Earth pics and two sets of Venus pics to publish, but Venus and
Earth
are somewhat well known. Mercury is mostly still unknown territory so I
want the mission to get there and start Mercury science while I am still
alive and interested, not 7 years down the road when many things may have
changed in both my life and the world at large.


True, and consider how the scientists whose jobs depend on this feel.

However, more than pretty pictures, people look at the bottom line and
appear to want cheaper rather than faster.

Allen W.

Why should mariner 10 in 1973 require 1 Venus flyby to set up 3 Mercury
flyby's and the 2004 Messenger mission require one Earth flyby, 2 Venus
flyby's and 3 Mercury flyby's before it actually goes into orbit in
2011?
Getting to Mercury is less energy intensive than getting to Jupiter.

Are you sure about that? I thought it was more intensive, since you
effectively have to lose all your momentum.

And going into orbit about a body is also more intensive then doing a
flyby.



You don't want to loose all your momentum, that puts you on a collision
course with old Sol himself, you just want to loose the difference in
orbital velocity for the Earth and Mercury, which is about the same energy
wise as a high asteroidal belt orbit or a Jupiter level orbit.

Going into orbit is a lot tougher than just doing a flyby, but we have done
it many times with Venus and Mars and we have suceeded in doing it with
Jupiter once, with Galelio.

Using
'energy saver' orbits is fine so long as you have all the time in the
world,
but NASA has developed the IMO bad habit of selecting the cheapest
orbits
no
matter what the time delay. To get people to vote and fund space
missions
you have to give them pretty pictures to look at. Maybe NASA is smarter
than I think because the way they are doing Messenger they will get a
nice
set of Earth pics and two sets of Venus pics to publish, but Venus and
Earth
are somewhat well known. Mercury is mostly still unknown territory so I
want the mission to get there and start Mercury science while I am still
alive and interested, not 7 years down the road when many things may
have
changed in both my life and the world at large.


True, and consider how the scientists whose jobs depend on this feel.

However, more than pretty pictures, people look at the bottom line and
appear to want cheaper rather than faster.


Bean counters are the same the world over, and if I hear one more time how
we can't afford more money on Space when SSI gets 100 times as much funding
with gross CPI raises every year I think I will puke.

Allen W.

"Allen W. McDonnell" wrote:

Going into orbit is a lot tougher than just doing a flyby, but we have done
it many times with Venus and Mars and we have suceeded in doing it with
Jupiter once, with Galelio.

Which sounds bad until you realize we have only tried it once - with
Galileo.

D.
--
Touch-twice life. Eat. Drink. Laugh.

On Sat, 27 Mar 2004 07:53:08 -0500, "Allen W. McDonnell"
wrote:

Why should mariner 10 in 1973 require 1 Venus flyby to set up 3 Mercury
flyby's and the 2004 Messenger mission require one Earth flyby, 2 Venus
flyby's and 3 Mercury flyby's before it actually goes into orbit in 2011?
Getting to Mercury is less energy intensive than getting to Jupiter.

Mercury and Jupiter aren't very different, in launch performance.
Getting to either one isn't that difficult... stopping when you get
there is. Galileo needed the most powerful launcher in the world and a
heavy IUS to get to Jupiter and have enough fuel to slow into orbit.
Ulysses used the same booster, plus a PAM, and went straight to
Jupiter, but it didn't have to stop there. Cassini used the most
powerful booster available, and still needed multiple gravity assists
to be able to enter Saturn orbit.

Using
'energy saver' orbits is fine so long as you have all the time in the world,
but NASA has developed the IMO bad habit of selecting the cheapest orbits no
matter what the time delay.

It's not just a NASA thing, look at the ten-year flight of Rosetta, or
BepiColombo's planned four year, multiple-gravity-assist flight plan
to Mercury. ESA has chosen this method also.

Oh, and "Deep Impact" will launch on a direct path late this year. No
gravity-assists.

Brian

"Allen W. McDonnell" wrote in
:

Getting to Mercury is less energy intensive than
getting to Jupiter.

My BOTE calculations show that a Hohmann transfer to Mercury requires a
delta-V of 17.5 km/s, while Jupiter requires only 14.4 km/s.

Intuition can be deceiving here.
--
JRF

Reply-to address spam-proofed - to reply by E-mail,
check "Organization" (I am not assimilated) and
think one step ahead of IBM.

"Allen W. McDonnell" wrote in
:
Why should mariner 10 in 1973 require 1 Venus flyby to set up 3
Mercury flyby's and the 2004 Messenger mission require one Earth
flyby, 2 Venus flyby's and 3 Mercury flyby's before it actually goes
into orbit in 2011?
Mariner 10 did fly-by's of mercury, Messenger will enter orbit. Orbit
requires plenty more delta-v than flyby only.

Getting to Mercury is less energy intensive than
getting to Jupiter.

Nope.
Jupiter is so much easier to reach that it is actually *cheaper* in delta-v
to fly out to jupiter and slingshot back to reach Mercury than to do a
direct transfer from earth to Mercury. The trip via Jupiter would just take
a *very* long time.

NO planet is as hard to reach as Mercury.

Add to this the non-trivial complexity of having your spacecraft withstand
over several years the solar intensity which is more than 11 times that we
get on Earth.

Now factor in a minuscule budget that only pays for a delta-II launch.
Without the multiple slingshot-flyby's, the launch would have demanded a
Delta-IVH or possibly even something more.

Its a miracle the mission is doable at all.