NASA / MARS REAL TIME LIVE........

Yep, cable rocks too!

Go!! Go!! Go!!

I can't wait for 90 days of Mars surface data to begin!

COOOOOOOOOL!

-JT

bobbyb wrote:

YES!! We are safely down on the planet!!!!

Jeff Taylor wrote:

ALL IS GOING WELL... might even see some pics thru the night....... brings back memories of the Sojourner Rover....... and Carl Sagan memorial station..

3D Panoramic...... views... YOGI etc....... still have my 3D glasses.

Not sure who is following this or not but the MACH 2 parachute deployment is IMPRESSIVE VERY impressive even for MARS..... then bouncing / rolling to a stop in just under 2 kilometers... with a cart the size of a mini golf cart..... real time data confirmed by multiple sources....

GREAT DAY to be a rocketeer......

Bobby B

yeah, that chute is awesome! what a big WHOP it must have made. I wonder what it was made of?

we watched the EDL animation a bunch of times and I just shook my head looking at the panels on that chute. I have to struggle to make a 6 panel chute. next stop, 32 panels of no doubt very finiky high tech cloth and probably invisible thread!

Good to be back, ain't it?

I just wish there were two probes sending signals from the Martian surface right now. Shame the European probe didn't work out, although I imagine there's still a chance....

Zooty

By the end of the month we should have 2 Spirit is one of 2..... landers......Opportunity is next.......

Spirit Mission:

Launch vehicle: Delta II 7925 Launch: June 10, 2003, from Cape Canaveral Air Force Station, Fla. Earth-Mars distance at launch: 103 million kilometers (64 million miles) Mars landing: Jan. 4, 2004, at about 2:30 p.m. local Mars time (signal received at Earth

8:35 p.m. PST Jan. 3) Landing site: Gusev Crater, possible former lake in giant impact crater Earth-Mars distance on landing day: 170.2 million kilometers (105.7 million miles) One-way speed-of-light time Mars-to-Earth on landing day: 9.46 minutes Total distance traveled Earth to Mars (approximate): 487 million kilometers (303 million miles) Near-surface atmospheric temperature at landing site: -100 C (-148 F) to 0 C (32 F) Primary mission: 90 Mars days, or "sols" (equivalent to 92 Earth days)

Opportunity Mission:

Launch vehicle: Delta II 7925H (larger solid-fuel boosters than 7925) Launch: July 7, 2003, from Cape Canaveral Air Force Station, Fla. Earth-Mars distance at launch: 78 million kilometers (48 million miles) Mars landing: Jan. 25, 2004, at about 1:15 p.m. local Mars time (signal received at Earth 9:05 p.m. PST Jan. 24) Landing site: Meridiani Planum, where mineral deposits suggest wet past Earth-Mars distance on landing day: 198.7 million kilometers (123.5 million miles) One-way speed-of-light time Mars-to-Earth on landing day: 11 minutes Total distance traveled Earth to Mars (approximate): 456 million kilometers (283 million miles) Near-surface atmospheric temperature at landing site: -100 C (-148 F) to 0 C (32 F) Primary mission: 90 Mars days, or "sols" (equivalent to 92 Earth days)

Bobby B

That gives you real perspective!

Jerry

Yea! I would like some of them MACH 2 parachutes. Could save a rocket or two. Stayed up all night watching NASA TV on the web, Great coverage. Glad to see I was not alone.

Mach 2 in LOCAL conditions.

Mars at substantial altitude.

Not Earth sea level.

Jerry

The full-scale parachute was tested at an equivalent dynamic pressure in the 80 x 120 ft wind tunnel at NASA Ames.

It is the dynamic pressure that dictates the mechanical loads, not the speed itself:

Q=0.5*rho*u^2

Q = dynamic pressure (N/m^2 or lbf/ft^2) u = velocity (m/sec or ft/sec) rho = density (kg/m^3 or slugs/ft^3)

ideal gas law: rho = P*w/(Rm*T) P = absolute pressure (N/m^2 or lbf/ft^2) w = gas molecular weight (kg/kg*mole or slug/slug*mole, its the same number) Rm = molar gas constant (8314 N-m/kg*mole-K or 49719.8 ft-lbf/slug*mole-R) T = absolute temperature (K or R)

Mars atmosphere is mostly CO2, molecular weight 44.01. Earth atmosphere in the wind tunnel is molecular weight 28.97 g/g*mole. As usually occurs in wind tunnel tests, we can match only one or two of the real flight parameters - hopefully the most important ones. The Mach number can't be matched without running the windtunnel at sub-atmospheric pressure (even bigger $$$). Reynolds number was also way low in the ground-based test. Since the flow field around an object (and therefore the aerodynamic loads) depends quite a bit on both Mach number and Reynolds number, one should also run some sub-scale tests across a range of Reynolds and Mach numbers to see how much of an impact they could have, as well as do some CFD (computational fluid dynamics) calculations at all of the wind tunnel conditions as well as for full-scale at Mars.

It is easy to see how the costs mount quickly to do this right, and even then it can all be for naught if someone doesn't make sure all of the sewing on the parachute panels is sound. On the other hand, if you test the flight article you can cause unseen damage that makes it fail in use. Many of the equipment failures experienced when trying to launch the shuttle are due to things getting worn out performing ground tests.

Brad Hitch

Here's a better link for the parachute tests at Ames:

Brad Hitch

Brad, awesome! thanks!!!

Brad Hitch wrote:

...

This is one thing that has bugged me since I first viewed the EDL video. I doubt that with a surface atmospheric pressure of about .01atm, that the speed of sound on Mars is anywhere near the speed of sound on Earth. I know that it's medium dependent, and I wish that people that know better would not refer to it as if it were some sort of absolute physical constant.

Regards,

Bob Bernatchez

NAR 29996

The is one thing that has bugged me since I've been reading rmr. Why to people jump to conclusions rather than actually research the answer. For example, the speed of sound on Mars is approximately 550mph, so in the EDL video when they say "about 1000 mph, or mach 2", they are stating the FACTS.

If you don't believe me, look here:

I wish that people that know better would not refer to things that they obviously have not researched before making an absolute big hairy thing of themselves in this enclave of quiet intellectual discussion that is rmr.

Regards,

David Erbas-White

There are parchutes desinged to decelerate ordinance from supersonic aircraft. You might find just what you need at a miltary surplus store.

David

chill, d0od! ever consider Tai Chi or Yoga?

"very effective techniques, they are" - Yoda

(ok, ok, Yoda didn't actually say that)

David Erbas-White wrote:

good advice though

nice ... nice ...

- iz ;)

I have one. It's 3 ft diameter and weighs *9 lb.*.

Tom

Well, that was certainly more heat than light.

The speed of sound in ideal gas mixtures is independent of pressure. It does depend on molecular weight, specific heat ratio and temperature, however, so you are correct in saying that it is medium dependent:

a = sqrt(gamma*(Rm/w)*T)

where gamma = Cp/Cv, the ratio of specific heat at constant pressure to the specific heat at constant volume Rm = molar gas constant (8314.5 N-m/kg*mol-K) w = mixture molecular weight (kg/kg-mol) T = absolute temperature (K)

Composition of the atmosphere (mole fractions):

Species w Mars Earth O2 31.99886 0.0015 0.20704 N2 28.01344 0.0270 0.77183 Ar 39.9481 0.0160 0.00926 (includes Xe, He etc.) CO2 44.00964 0.9550 0.00033 H2O 18.01532 0.0005 0.01154 (50% RH @ 20 C, Sea level) -------- --------- 1.0000 1.00000

so w(Mars) = 43.48174 kg/kg*mol gamma(Mars) = ~1.3 w(Earth) = 28.839 kg/kg*mol gamma(Earth) = 1.4

Ambient surface temperature on Mars ranges from 30 to -170 F (0 to

-110 C). At 0 C (273 K, a balmy day) the speed of sound on Mars is

260 m/sec, going down to ~200 m/sec on the coldest day. On Earth at 20 C the speed of sound is 344 m/sec - about 30% higher than the "hot" day on Mars, declining to ~300 m/sec at airliner cruise altitude where the ambient T can be down to -60 F. The speed of sound on the surface of Mars is therefore approximately the same as exists at 35,000 feet on Earth.

Brad Hitch

Another thing to remember is that while MACH 2 sounds really cool, the dynamic pressures involved are much less impressive.

I remember learning this from Burt Rutan at one of the the Oshkosh talks he gave. He said that for his X-Prize entry, at the highest MACH number part of his flight, he was at extreme altitudes and thus low atmospheric pressures. He gave a example for the pilots in the audience saying that if you used the airspeed indicator you'd find in a Cessna it would only be reading something like 160 kts. This would be in the same sort of speeds as you might encounter in one of his homebuilt designs.

By way of this example, he was showing that the sort of construction techniques the crowd was familiar with were not far from what was needed for flying in near space conditions. He did qualify this with the notion that you were still flying supersonically, so the aerodynamics would need to be different. He specifially said that you wouldn't want to do this in a rocket powered Long-Ez.

You can see an example of this in the NOVA episode where they are testing the parachute in a wind tunnel. They are duplicating the dynamic conditions the parachute will encounter even though you could walk up the the parachute and touch it without being blown away.

Shawn