Sensor setup lifetime and interfacing with Arduino Uno question

I am using the following sensors for an rocket project utilizing an Arduino Uno for stage separation and parachute deployment. I was planning on having an Arduino Uno powered through a 9V battery, and was wondering how long this setup would last. I don't want to lose power before the launch, while the sensors are not on sleep mode, and certainly not during flight which may last 90 seconds.

Both of these support I2C and can connect to analog pins 4 and 5 on the Uno, and can be powered with 3.3V. My other question is, can I put them on an a rocket electronics bay with an Arduino without a mux board? The mux would be fairly large to accommodate.

MPL115A2 Pressure Sensor Current Draw: 5uA during active mode 1uA during sleep mode Range: 2.4V-5.5V (can use with 3V or 5V microcontroller)

ADXL345 +-16g max rating Accelerometer Current Draw: Ultra Low Power: 40uA in measurement mode, 0.1uA in standby@ 2.5V Range: 2.0V-3.6V

The Arduino Uno is not very power efficient, but it will last some time on a 9V battery.
I would strongly advise to use a board with a ceramic oscillator, it have take more g-shocks. Or a board without external crystal or oscillator.

You could have a look at the Arduino Pro Mini board, but that requires an additional adapter to upload a sketch.
If you search Ebay for “Arduino Pro Mini” you see that they are less than 3 dollars. I would not recommend those from Ebay, they use the cheapest components and have sometimes bad soldering.

The Arduino Micro is smaller, it doesn’t need an extra adapter, but it still has a crystal.

What kind of power is needed to seperate the stage and deploy the parachute ?
Some Arduino boards can be powered directly from a Li-po cell.

Is a mux a breakout board with connecters ? You don’t need that at all.

Caltoa: Is a mux a breakout board with connecters ? You don't need that at all.

In electronics, a multiplexer (or mux) is a device that selects one of several analog or digital input signals and forwards the selected input into a single line

So I don't need any additional connections to accommodate the sensors? The two sensors will be able to connect to the board on their own?

Sorry, I didn't understand your question very well.

The I2C bus is designed to be used with many devices. They all are connected to the SDA and SCL. Each device has its own I2C address, so the Master is able to talk to each device. In this case the Arduino Uno is the Master.

I think the I2C address for the ADXL345 is 0x53 and for the MPL115A2 is it 0x60. If you run the i2c_scanner, it should see both. http://playground.arduino.cc/Main/I2cScanner

The Arduino Uno is running at 5V, but the ADXL345 may not be connected to a I2C 5V bus. Power both of them with 3.3V, connect both of them to the I2C bus (SDA and SCL). That way it should work. Don't add extra pull-up resistors to 5V, and never add a sensor board that has pull-up resistors to 5V.

Thanks so much, Caltoa! I really appreciate it.