Search Exo Cruiser

Dec 9, 2014

NASA Plans Next Orion Missions 2017 and 2019

After the succesful EFT-1 (Exploration Flight Test 1) Orion mission (see the previous article in this blog) NASA is planning to launch Orion again in 2017 (EM-1, Exploration Mission 1) and 2019 (EM-2, Exploration Mission 2).

Dec 8, 2014

NASA's Orion EFT-1 Successful

NASA's new spacecraft Orion made a successful flight test Dec. 5, 2014. The mission (EFT-1, Exploration Flight Test) took 4 and ½ hours and circulated twice the Earth. The peak altitude was just under 6000 km (3600 mi) above sea level.

Nov 28, 2014

Count Down for Orion EFT-1 Starting

EFT-1 should launch about December 4th, 2014.

[The EFT-1 liftoff happened Dec. 5, 2014, 7:05 ET. There were three attempts to launch it Dec. 4th but unsuccessful, two first attempts were interrupted by winds and the last one by a train valve which did not work properly. Then the launch window closed and further attempts shifted to the next day.] 

Nov 25, 2014

MEOSAR Medium-altitude Earth Orbit Search and Rescue [Service]

The MEOSAR uses GNSS (Global Navigation Satellite System) satellites that are primarily used for positioning, navigation and timing. As a secondary mission, satellites in the USA GPS constellation, the European Galileo constellation and the Russian GLONASS constellation have Search and Rescue equipment on the satellites.

The current Low-altitude Earth Orbit Search and Rescue (LEOSAR) satellites are being replaced with a new Medium-altitude Earth Orbit Search and Rescue (MEOSAR) satellite system.

The MEOSAR system will detect beacons in almost real-time (i.e within 5 minutes). If the beacon is detected by three or more MEOSAR satellites, then the location of the beacon will be determined as well. When the full constellation of MEOSAR satellites is in operation, this will mean location will be determined within 10 minutes, 95 per cent of the time.

ACR personal locator with GPS
[GPS-based Distress radio beacons, registered:

The most modern 406 MHz beacons with GPS (US$ $300+ in 2010) track with a precision of 100 meters in the 70% of the world closest to the equator, and send a serial number so the responsible authority can look up phone numbers to notify the registrator (e.g. next-of-kin) in four minutes.

The GPS system permits stationary, wide-view geosynchronous communications satellites to enhance the doppler position received by low Earth orbit satellites. EPIRB beacons with built-in GPS are usually called GPIRBs, for GPS Position-Indicating Radio Beacon or Global Position-Indicating Radio Beacon.

However, rescue cannot begin until a doppler track is available. The COSPAS-SARSAT specifications say that a beacon location is not considered "resolved" unless at least two doppler tracks match or a doppler track confirms an encoded (GPS) track. One or more GPS tracks are not sufficient.]

The new MEOSAR satellites will be launched by the Russian Federation, the European Union and the USA. An operational constellation is expected to be in place by 2017.

The MEOSAR system consists of MEOSAR satellites that detect emergency distress beacons (EPIRBs, PLBs and ELTs). The satellite sends the beacon message back to earth where it is detected by a MEOLUT (MEOSAR Local User Terminal). With sufficient information, the MEOLUT will generate a location for the distress beacon. The beacon activation information is forwarded to a Mission Control Centre (MCC) and then to the relevant Rescue Coordination Centre (RCC) which responds to the beacon activation.

The three MEOSAR satellite constellations will use transparent repeater instruments to relay 406 MHz beacon signals, without on-board processing, data storage, or demodulation/remodulation. MEOSAR satellite providers will make their satellite downlinks available internationally for processing by MEOLUTs operated by MEOSAR ground segment participants.

MEOSAR search and rescue system components

How does MEOSAR work?

The above diagram shows the major components of the MEOSAR system:

1. A distress beacon is activated and sends a 406MHz message. The message includes the beacon id (also known as the Hex id or UIN). If the beacon has a GPS, the message will include the GPS location.

2. Any MEOSAR satellites that detect the distress beacon relay the message back to earth on 1544.1MHz. The relayed message is detected by a MEOLUT.

3. If a MEOLUT receives sufficient information (typically, relay from three or more MEOSAR satellites) a location for the beacon can be calculated. The MEOLUT sends all information available from the beacon (the beacon id, the GPS location if it exists and the MEOSAR location if it can be calculated) to its associated Mission Control Centre (MCC).

4. The MCC forwards beacon information to the relevant Rescue Coordination Centre (RCC). If the beacon was located in New Zealand, for example, the beacon information would be forwarded to the New Zealand RCC in Wellington. If the beacon as located in Australia, the information would be forwarded to RCC Australia in Canberra.

5. The RCC then coordinates the search and rescue associated with the beacon activation.




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Nov 23, 2014

Galileo Started Badly (August 22, 2014)

Europe's satellite navigation system Galileo's full operational capability (FOC) phase started badly (22.8.2014) due to a design error in the Russian launch vehicle Soyuz-STB Fregat-MT. This is the first partial failure since 2011 for the Soyuz vehicle and about 20 successful launches since the 2011 failure. The problem left the pair of satellites (FOC-1 and FOC-2) in the wrong orbit, with higher apogee, lower perigee and an incorrect inclination compared to the planned circular orbit (see below).

[News update Jan. 5, 2015: After some maneuvers the FOC-1 orbit could be fixed to some degree and the same recovery maneuvers are planned for the sixth satellite (FOC-2), taking it into the same orbital plane but on the opposite side of Earth. The decision whether to use the two satellites for Navigation and SAR purposes as part of the Galileo constellation will be taken by the European Commission based on the test results later.]

Galileo FOC-1 and FOC-2 orbit errors

“After launch, we quickly discovered that one of each satellite’s pair of solar wings had not deployed correctly,” says Liviu Stefanov, Spacecraft Operations Manager. “At the same time, difficulties in receiving radio signals – indicated by unusually low power and instability – alerted us to the fact that the orbits could be incorrect. Basically, the ground stations were pointing to where we expected the satellites to be, and they weren’t there, so we weren’t getting good signals.”

It took three days to release the trapped solar wing of the first satellite, and then two days later the second Galileo’s stuck array was also freed.

Galileo FOC Satellites

It was determined that the best course of action would be to dedicate most of the vehicle’s propellant to raising the perigee (lowest point) of the orbit from 13,713 to 17,339 Kilometers. Once in that orbit, the satellite would be out of the most intense areas of radiation. Although the two spacecraft will not reach  their nominal working orbit, “the new orbit will fly over the same location every 20 days,” said Daniel  Navarro-Reyes, ESA Galileo mission analyst. “The standard Galileo repeat pattern is every 10 days, so achieving this will synchronize the ground track with the rest of the Galileo satellites.”

Soyuz 2-1B, Galileo FOC-1 and 2 Launch, August 22, 2014

Galileo FM01 is a 733-kg (660 kg dry) navigation satellite, one of the first two Full Operational Capability (FOC) satellites. These satellites carry two rubidium and two hydrogen maser atomic clocks and broadcast on L-band. They also carry the MEOSAR search and rescue transponder payload. They are built by OHB (Bremen) with navigation payloads by SSTL (Guildford). The earlier IOV test satellites were partly owned by ESA, but the FOC satellites are owned by the European Union's GSA (Global Navigation Satellite Systems Agency).

The spacecraft were placed in a wrong orbit. As planned, the Fregat upper stage made its first burn to put both satellites into in elliptical transfer orbit and then made a second burn intended to circularize the orbit at 23,500 km, inclined at 55.0 degrees. Unfortunately, the orbit was 13,700 km x 25,900 km, inclined at 49.7 degres, more elliptical than planned and with the wrong orbital inclination.

Russian officials report that the failure of the Fregat stage was caused when a cryogenic helium line installed too close to a hydrazine propellant supply line caused the hydrazine to freeze. The root cause was a design error, not a quality control error.

On 22 August, at 12:27 GMT/14:27 CEST, a Soyuz rocket launched Europe’s fifth and six Galileo satellites from Europe's Spaceport in Kourou, French Guiana. Rewatch the moment of launch here.






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Nov 18, 2014

The Dornier Do. X

Dornier Do. X at the Bodensee (Lake Constance), at the left Dornier-Werke GmbH factory buildings at Altenrhein Switzerland near Austria-Germany-Switzerland border crossing

Sep 18, 2014

(Airplane Electronic) Flight Computer Formulas

Theory and Formulas Behind (Airplane) Crosswind Calculations

 There are several mechanical and electronic flight computers available nowadays. Most problems can be solved with very simple arithmetics and using a simple pocket calculator but some calculations to predict wind effects require more complex formulas. Those are solved here.

Airplane in crosswind

This theory applies to all moving objects since it uses actual true air speeds involved in the situation. That will already account for all kind of factors such as air resistances etc.

Jeppesen TechStar electronic flight computer can calculate wind effects

It is assumed that the air moves evenly. The following figure illustrates the variables involved in the calculation.

Variables used in the calculations

When doing pre flight planning we usually want to know how wind affects our route legs

  • 1) what is the resulting ground speed (Vg) and to which direction (HDG) to steer to compensate for the crosswind or
  • 2) what is the wind when we know the ground speed (Vg) and air speed (Vo) and the heading (HDG) and Course Over Ground (COG).

Notice that if in the second case both air and ground speeds are equal and HDG and COG are equal then there is NO wind at all.

Object (Airplane) knowns
  • Vo - air speed (desired cruise speed or pitot measured)
  • COG - direction (desired COG or GPS measured)

Wind knowns or solve
  • Vw - speed
  • alpha - direction ("where from" is given)
Object knowns or solve
  • Vg - resulting ground speed (to solve time and fuel required)
  • HDG - heading to steer (to assist to fly the trip)

The basic formulas are obtained from the facts that if we want to follow some predefined COG and if we have crosswind we have to steer into the wind so much that the cross track speed component of the wind is nulled. When that equation is solved we obtain also wind and side slip generated track speed components. All speed components are simply added along COG x and y axes. Using these formulas different unknowns can then be solved as required.

To stay on cours (COG) Voy must be equal to Vwy
Additionally we use the following variables.

  • delta - side slip angle (add this to COG to get HDG)
  • beta - effective wind angle ( =  alpha - COG)
  • Vwx and Vwy - wind speed components along COG
  • Vox amd Voy - air speed components along COG

To stay on the desired COG track Voy must be Vwy so we can write:

Voy = Vwy (1)

and when that is met (by adjusting side slip angle delta) we also have the ground speed available along the COG x axis and for that we can write:

Vg = Vox - Vwx (2)

These two main equations can futher be written as:

Vo*sin(delta) = Vw*sin(beta) (3)

Vg = Vo*cos(delta) - Vw*cos(beta) (4)

Since all directions are given relative to the north we can also write:

HDG = COG + delta (5)

beta = alpha - COG (6)

Using these basic equations we can now solve the 2 cases given and any 2 unknowns if required.

Case 1) Unknown Heading and Ground Speed

To solve heading (HDG) first using (3) solve delta.

delta = asin(Vw*sin(beta)/Vo) (7)

and from (5), (6) and (7) we get.

HDG = COG + asin(Vw*sin(alpha - COG)/Vo) (8)

To solve ground speed using (4), (6) and (7) we get.

Vg = Vo*cos(delta) - Vw*cos(alpha - COG) (9)

Now since all variables in (8) and (9) are know we can solve Vg and HDG. Let's consider the following example.

Example 1

During flight planning you determine that the forecast winds aloft at your cruising altitude are 080 degrees at 20 knots. Your course and true airspeed will be 030 degrees and 170 knots, respectively. Using the above equations, you compute the true heading and groundspeed as follows.

Vo = 170 knots
COG = 30 degr

Vw = 20 knots
alpha = 80 degr

Vg = ground speed, knots = ?
HDG = airplane heading, degr = ?

Using above formulas we get as follows.

delta = asin(Vw*sin(alpha - COG)/Vo)
= asin(20*sin(80-30)/170)
 = 5.17 degr

Vg = Vo*cos(delta) - Vw*cos(alpha - COG)
= 170*cos(5.17) - 20*cos(80-30)
= 156.45 knots

HDG = COG + delta
= 30 + 5.17
= 35.17 degr

So our ground speed will be 156.45 knots and we should steer to heading 35.17 degrees. This amount of side wind from given direction requires 5.17 degrees crab angle to the wind.

Case 2) Unknown Wind

In case of unknown wind we know the crab angle or heading and COG and also airplane Vo and ground speed Vg. Using (3) and (9) we get.

Vo*sin(delta) = Vw*sin(alpha - COG) (10)

Vg = Vo*cos(delta) - Vw*cos(alpha - COG) (11)

To solve alpha we first solve from (10) Vw

Vw = Vo*sin(delta)/sin(alpha - COG) (12)

and then insert Vw into (11)

Vg = Vo*cos(delta) -


= Vo*cos(delta) - Vo*sin(delta)/tan(alpha-COG)

and finally solve alpha.

tan(alpha-COG) = -Vo*sin(delta)/(Vg-Vo*cos(delta))

alpha-COG = atan(-Vo*sin(delta)/(Vg-Vo*cos(delta)))

alpha = atan(-Vo*sin(delta)/(Vg-Vo*cos(delta)))+COG (14)

Now calculate wind angle alpha first and then insert it into (12) to get wind speed Vw.

Example 2

For this example you want to calculate the actual winds aloft using a course of 175 degrees, actual heading of 160 degrees, true airspeed of 180 knots, and actual groundspeed of 144 knots. Now, using the above formulas solve the wind variables.

COG = 175 degr
HDG = 160 degr
Vo = 180 knots
Vg = 144 knots

Solve Wind
alpha = wind angle, degr = ?
Vw = wind speed, knots = ?

Using the formula (14) and (5) we get.

delta = HDG - COG = 160 - 175 = -15

alpha = atan(-Vo*sin(delta)/(Vg-Vo*cos(delta)))+COG
= atan(-180*sin(-15)/(144-180*cos(-15))) + 175
= 117.66 degr

and from (12) we get.

Vw = Vo*sin(delta)/sin(alpha - COG)
= 180*sin(-15)/sin(117.66 - 175)
= 55.34 knots

So our wind is 117.66 degrees at 55.34 knots.

xCalc - Expression Calculator

You can enter the above formulas to your computer using some programming language and that should do the job. If you need a desktop calculator for your Windows PC that can solve those expresions you can also download a free expression calculator "xCalc" from the link below. That will accept directly the above expressions. xCalc acts almost like the programming language BASIC interpreter used in the direct calculation mode.

Link to xCalc

Flight Computer Videos

E6B Flight Computer from Sporty's Pilot Shop

E6B Flight Computer: Ground Speed and True Heading

E6B Flight Computer: Unknown Winds


/1/ Jeppesen - Private Pilot Manual


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Aug 29, 2014

LM Descent to the Moon - Part 2 - Hardware

This part (2) will handle the LM descent hardware in more detail. See part 1 for more general description of the Apollo Lunar Module landing theory and software.

Aug 25, 2014

LM Descent to the Moon - Part 1 - Theory and Software

The LM descent from the CSM (Command Service Module) parking orbit (approximately 62 by 58 nautical miles above Moon surface) is illustrated in the following figure. After the LM and the CSM have undocked and separated to a safe distance of several hundred feet, the LM performs the DOI (Descent Orbit Insertion), which is the first and simplest of the two descent maneuvers.

LM Descent

Aug 19, 2014

Digital's DECSYSTEM-20 - Part 8 - I/O Bulkheads


The DECSYSTEM-20 bulkheads for connecting peripheral devices were located on the back of the mainframe: Basically they were the MASSBUS (I/O processor cabinet) and UNIBUS (front end processor cabinet) bulkheads for connectors.

Apr 8, 2014

Digital's DECSYSTEM-20 - Part 7 - Console


The KY11-C Console was located in the cabinet # 1 on the high right (see next picture).

Cabinet # 1 (front end processor cabinet)

KY11-C Console Panel abowe the PDP-11/40 drawer

Digital's DECSYSTEM-20 - Part 6 - Power


As all old mainframes so was DECSYSTEM-20 (PDP-10 / KL10) also power hungry. That was due to the development coal that speed was always desired over energy saving.

DECSYSTEM-20 had enough power to serve as a heater in a sauna

Apr 6, 2014

Digital's DECSYSTEM-20 - Part 5 - CPU (KL10)

CPU CABINET - Cabinet # 3 (Part 5)

The  KL-10 (in DECSYSTEM-20) introduced in 1974 was a 36-bit word size, magnetic core (later semiconductor) memory, capacity of 32K to 4096K (4M) words 500 nanosecond instruction cycle, 1.8 MIPS CPU. The fast speed was partially  possible due to the cache memory technology.

Magnetic core memory. 1951 Jay Forrester filed a patent application for the matrix core memory. Core memory was born

Apr 5, 2014

Digital's DECSYSTEM-20 - Part 4 - Input/Output for CPU


The I/O cabinet connected the main processor KL10 to the peripherial devices via MASSBUS or UNIBUS (see the following picture). MASSBUS was for fast and large amounts of data transfer and UNIBUS was for slow terminals, printers and similar.

DECSYSTEM-20 block diagram

Apr 4, 2014

Digital's DECSYSTEM-20 - Part 3 - Front End (PDP-11/40)

 FRONT END CABINET (PDP-11/40) (Part 3)

As already told before in this article series the DECSYSTEM-20 (PDP-10 / KL10) was delivered in 3 cabinets as seen in the following picture. The front end processor (PDP-11/40) was located in the number 1 cabinet, the left most, with the expansion drawer to hold application specific variable system parts. The whole system could have more than 3 cabinets if more space was required.

Cabinet # 1 the left most cabinet

Digital's DECSYSTEM-20 - Part 2 - Cabinets


DECSYSTEM-20 and some of its peripherial devices

Mar 31, 2014

Digital's DECSYSTEM-20 - Part 1 - External Parts

As a younger engineer I used to use some Digital's multiuser timesharing computers for program development but never actually studied them very deeply at that time. So I might research one such a computer and share my findings with you.

digital logo

Jan 20, 2014

RF Turner Electronic Circuits

In a search for a RF module which would do everything and be programmed with a MCU I visited several PLL based electronics designs just to find out that nowadays you can get also the MCU included in that single chip RF solution. For example Silicon Labs and Analog Devices have very modern circuits which include PLL, VCO and MCU in a single IC. Lets view some less integrated interesting designs now.

How a modern (20 years modern) RF tuner circuit works

Here is a block diagram of a French design Synthe_BB209 and Synthe_POS150 (see REF /1/). Both are very similar but the latter uses POS150 module as the VCO where as the first one uses discrete components.

20 years modern RF module includes PLL and VCO which are controlled using a MCU.