NASA launches exo-brake parachute from ISS

Nov 27, 2013
Credit: NASA

Mission controllers have confirmed that a small satellite launched from the International Space Station last week has successfully entered its orbit. Soon it will demonstrate two new technologies including an "exo-brake" device to demonstrate a new de-orbit technique as well as a communications system to provide precise information about the spacecraft's position.

The satellite, dubbed "TechEdSat-3p," arrived at the station aboard a Japanese H-II Transfer Vehicle Aug. 3. It was released at 2:58 a.m. EST Nov. 20, from the same Japanese Small Satellite Orbital Deployer aboard the station that launched its smaller predecessor - TechEdSat - in 2012.

"TechEdSat-3p will be the first nanosatellite of its size - a three unit cubesat - deployed from the International Space Station," said Marcus Murbach, the TechEdSat-3p principal investigator at NASA's Ames Research Center at Moffett Field, Calif.

The International Space Station is converging science, technology and human innovation to demonstrate new technologies and make research breakthroughs not possible on Earth. Launching nanosatellites to test technologies necessary for deep space exploration is just one example of how the space station is being used to as a springboard to NASA's next great leap in exploration, including future missions to an asteroid and Mars.

The primary experiment onboard TechEdSat-3p is called the "exo-brake" and is a specially-designed braking device that operates at extremely low pressures and operates similar to a parachute. The exo-brake on TechEdSat-3p will be the first to perform a rapid de-orbit and re-entry from Earth's outer atmosphere. Engineers believe exo-brakes eventually will enable small samples to be returned from the station or other orbital platforms.

TechEdSat-3p also is equipped with a short-burst data modem provided by Iridium Communications Inc. of McLean, Va. The modem will be combined with a GPS receiver to perform communications functions including providing data about the spacecraft's health and the space environment.

"TechEdSat-3p uses a completely new nanosatellite communication paradigm in that the Iridium and GPS orbiting spacecraft replace ground stations for tracking, rapid data retrieval and uplink capability," said Murbach. "Eventually, these technologies could be combined to provide another way to return cargo from the space station or other orbiting platforms."

TechEdSat-3p is the second satellite in the TechEdSat series to successfully achieve orbit. The TechEdSat series uses the cubesat standards established by the California Polytechnic State University in San Luis Obispo, that specifies nanosatellites in one unit (1U) increments of 10 cubic centimeters (approximately four cubic inches). TechEdSat-3p is a 3U satellite and weighs approximately five pounds.

Previously, the TechEdSat-1 - a 1U cubesat - successfully demonstrated the use of basic communications subsystem and a radiation-tolerant controller. It functioned in orbit for seven months until it re-entered Earth's atmosphere. This mission was followed by a successful Iridium system flight test in April during the maiden flight of Orbital Sciences' Antares-1 rocket.

"The satellite's structure, avionics and payload were custom-designed by the team to utilize the 3U volume most efficiently and provide ample space for the exo-brake deorbiter," said Murbach. "The hardware was mostly off-the-shelf components available to anyone - this makes it easier to reproduce and make adjustments for future flights."

For example, the TechEdSat-4 satellite, proposed for launch in 2014, will be very similar to the TechEdSat-3p design. It will develop further the exo-brake passive deorbiting system by adding drag-modulation for accurate de-orbit and eventual re-entry control. Future TechEdSats also will validate hardware for possible nanosatellite missions to the surface of Mars.

"This project uniquely pairs advanced university students with NASA researchers in a rapid design-to-flight experience," said Periklis Papadopoulos, TechEdSat co-investigator at San Jose State University in California. "It also provides a platform to test technologies for future NASA Earth and planetary missions, as well as providing students with an early exposure to flight hardware development and management."

TechEdSat-3p was developed, integrated and tested at Ames by student interns from San Jose State University and the University of Idaho. TechEdSat-3p is funded by Ames. The total cost in parts was less than $50,000 because the team primarily used only commercial off-the-shelf hardware and simplified the design and mission objectives.

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Eikka
3 / 5 (6) Nov 27, 2013
cubesat standards established by the California Polytechnic State University in San Luis Obispo, that specifies nanosatellites in one unit (1U) increments of 10 cubic centimeters (approximately four cubic inches).


Cubesats and nanosats aren't the same standard. Cubesats unit size is 10 centimeters cubed, not 10 cubic centimeters which is 1 centiliter instead of 1 liter in volume.

Neither is anywhere near four cubic inches.

(1 cm)^3 = 1 cm^3 = 1 ml
(2.154 cm)^3 ~ 10 cm^3 = 1 cl
(2.54 cm)^3 ~ 1 in^3 = 1.6 cl
(4 x 2.54 cm)^3 ~ 4 in^3 = 6.6 cl
(4.64 cm)^3 ~ 100 cm^3 = 1 dl
(10 cm)^3 = 1000 cm^3 = 1 l
RealScience
5 / 5 (3) Nov 27, 2013
@Eikka - good catch.

Unfortunately this is a fairly common mistake. People often mistake a 10-centimeter cube as being 10 cubic centimeters, forgetting the the '10' gets cubed as well as the centimeters.

And in this case 10 cm is ~4 inches, so the writer merely repeated the mistake again, forgetting to cube the '4' as well as the inches.

How common a mistake is it? In the list of six calculations you gave, you made it once:
(4 x 2.54 cm)^3 ~ 4 in^3 = 6.6 cl is NOT correct.

(4 x 2.54 cm)^3 = 64 in^3 = ~1 liter rather than 6.6 cl.
Mike_Massen
2.3 / 5 (6) Nov 28, 2013
Issue illustrates problem the predisposition US has for imperial units, it already caused the loss of a mars mission (at least).

World with exception of US & one or two other 3rd world countries use the metric system.

Converting from one to the other is replete with potential for errors as Eikka demonstrated so well, yet had the intention of showing up errors, which is commended but, ironically made a doozy.

Eikka & I had a debate on the topic of energy to push a vehicle along at a fixed speed a year or so ago, my records & all calculations were in metric & illustrated that when minimising various losses & exploiting good instrumentation one could demonstrate the figure could be comparatively low & in KW. IIRC, Eikka did his figures in imperial, which made it difficult for him, time elapsed on the commenting period & I didn't pursue it.

Sentimental US imperialists who insist on old measures; inch, foot derived from a King illustrate stubbornness & not intelligence, errors continue.
Eikka
2 / 5 (4) Nov 28, 2013
(4 x 2.54 cm)^3 ~ 4 in^3 = 6.6 cl is NOT correct.


That was rather a case of misplaced parentheses. The intention of that line was to calculate the volume of four cubic inches in metric, not 10.16 cm cubed.

And it is indeed ~6.6 cl
Eikka
2.6 / 5 (5) Nov 28, 2013
Eikka & I had a debate on the topic of energy to push a vehicle along at a fixed speed a year or so ago, my records & all calculations were in metric & illustrated that when minimising various losses & exploiting good instrumentation one could demonstrate the figure could be comparatively low & in KW. IIRC, Eikka did his figures in imperial, which made it difficult for him, time elapsed on the commenting period & I didn't pursue it.


You're thinking of someone else.

I never do my physics in imperial. I may present the results as converted to miles and feet and gallons etc. because it's more easy to relate to.

The problem with SI is that it doesn't really have units of useful size. I often ask metric people to show with their hands a meter, and they show me about 2-3 feet because the meter is actually pretty big in human terms. Getting the centimeter right is also a gamble because it's such a small measure.
Eikka
2.6 / 5 (5) Nov 28, 2013
Shopkeepers on the other hand do better with the meter, because they've learned that to . measure a rough meter of wire or hose by hand they need to pull from the left shoulder to the right hand, so they know it's longer than one would expect.

But where they too fail is when you ask what a centimeter is. They show "about so" with their fingers and that can be plus minus 5 mm or 50% error on the actual value, whereas the same error as applied to the inch would be 20%.

Practically nobody I've met has any intuition about how long a kilometer is, because over long distances people measure things by the time it takes to get there. At 60 mph you cover exactly a mile per minute, so that's easy to relate to. At 65 mph a bit more, but the error isn't that big.

At 100 kph you travel 1.67 km/min. Quick! How far will you get in 35 minutes? How long does it take to travel 35 km?

The only practically useful measure I've found is the liter and its fractions.
Eikka
2.6 / 5 (5) Nov 28, 2013
And perhaps the kilogram, but that again has to be converted by a multiplier of ~9.8 in order to get what you're really asking for which is how much it actually weighs, because in most physics problems you're dealing with forces instead of masses.

That's why the soviets, instead of using Newtons, actually calculated their entire space program using a non-standard unit kgf which is defined to be 9.807 Newtons so they wouldn't have to deal with the back and forth conversions. It has the same utility as pounds of thrust.

And the final irony is that all the building supplies in metric countries, be it plywood sheets or plumbing supplies, are sized to fit closely within the imperial standards.
Eikka
2.6 / 5 (5) Nov 28, 2013
Sentimental US imperialists who insist on old measures; inch, foot derived from a King illustrate stubbornness & not intelligence, errors continue.


The fact that they're based on some king's nose is secondary - the fact that they're based on someone's nose or foot is paramount because they're based on human metrics, not some arbitrary "we'll divide the circumference of the earth into 40,000 parts" metric. The units are based on how large peoples' body parts are, how much they eat or drink, how much they can carry etc. so they make sense. People interact with similiar quantities all the time, so they know them intuitively.

The only problem with the imperial is that we don't count in base-12 anymore, and it was never systematically applied across the board, so the units are difficult to relate to one another. If you decimalized and unified the system, it would work just fine. Better even.
RealScience
not rated yet Nov 29, 2013
(4 x 2.54 cm)^3 ~ 4 in^3 = 6.6 cl is NOT correct.


That was rather a case of misplaced parentheses. The intention of that line was to calculate the volume of four cubic inches in metric, not 10.16 cm cubed.


Ah, so you were trying to REPLICATE the author's mistake to show how it was indeed a mistake, and when typing that line you unintentionally corrected the very mistake that you were trying to replicate.

If you are used to correcting calculation mistakes it can become automatic, so that makes sense.

RealScience
not rated yet Nov 29, 2013
@Eikka - I agree that metric's advantages are not intrinsic, but they do exist:

1) Metric is based on powers of ten, and humans now almost exclusively use base 10.

2) It is much newer, so that there is, for example, only one liter as opposed to imperial gallons, US gallons, dry gallons, etc.

3) All units are derived to stem from a minimum set of arbitrary units, as opposed to surveyors using chains, sailors using fathoms, machinists using gauges, etc.

4) It is a global standard.

Without devices (as you point out), we carry an approximate inch and foot with us at all times (and a mile is a thousand paces). Also simply by dividing intervals in half one can measure fractions of an inch to great accuracy.

But when one has measuring devices I see no advantage for imperial (and people like us who still approximate can generally convert in their heads anyway).

And while imperial COULD be simplified, metric is ALREADY simplified, so I prefer metric for everything except carpentry.
MIBO
not rated yet Dec 01, 2013
Metric makes more sense since it is based on a universal standard, i.e. 1L of water at STP has a mass of 1Kg, Imperial measurements are not. Using a measuring system based on peoples body size which was invented hundreds of years ago is stupid since the average person was considerably shorter back then.
We care about forces and mass much more than we care about weight, the concept of Newton-Metres for torque for example is much easier to work with than foot-lbs.
With metric measurements there is no arbitrary scaling factor to remember which reduces mistakes, 1N accelerates 1Kg by 1M/s regardless of what planet you are on as Kg is a unit of mass, not weight. It is common for scientists to work in Metric and convert the results for human consumption, but most scientists I know prefer the metric units, the conversion to imperial is usually for the scientifically uneducated, and for the older generation who grew up with imperial measurements
MIBO
not rated yet Dec 01, 2013
@RealScience,
1Km is about a thousand paces, 1Mile is 1760 yds, or 5280ft, so you might cover it in 1000 paces if you were running, but the average step size is probably closer to between 2.5 and 3.5 feet depending on the height of the person. Which I guess goes further to prove your point.
MIBO
not rated yet Dec 01, 2013
imperial get worse the further you look, why are munition charges measured in Grains, which appears to be based on the weight of a grain of Barley from some time long ago. In archery we measure arrow weight in Grains and the first thought I always have is "What's that in grams".
RealScience
not rated yet Dec 01, 2013
@MIBO - A pint of water is one pound, and it takes 1 BTU to raise 1 pound of water by 1 degree F. (Using mass is slightly better because a pint of water is not a pound on the moon, but anyone dealing with exotic circumstances can convert.)

A 'pace' is a step with each foot, so if the average step is just over 2.4 feet then 1000 paces is a mile.

1/10,000,000 of the quadrant of one planet is really as arbitrary as using an average body part (and harder to approximate).

In imperial a 'slug' is the unit of mass, and 1 pound of force accelerates 1 slug of mass by 1 foot per second squared, no mater what planet you are on.

And while lay people use a pound as if it were a unit of mass, ask someone their weight in metric units and essentially everyone will answer in 'kilos' rather than Newtons.

In imperial the units themselves made sense WITHIN their domains.

Today metric makes more sense because it is standardized ACROSS domains, and because it is decimalized (except time).
MIBO
not rated yet Dec 01, 2013
@RealScience - The problem with imperial is not that there is no unified base unit, but that the larger units are arbitrary multiples which means that there are conversions to be applied when different units are specified and this is where mistakes are made.
Where is the sense in a measurement system that has different multiples throughout.
12 inch = 1 foot, 3 feet =1 yard, 22yds = 1 chain, 10 chains = 1 furlong, 8 furlongs = 1 mile.
not to mention fathom, link, cable, rod, nauticle mile.
so how can a set of distance ratios 12,3,22,10,8 be a sensible approach regardless of what number base you operate in, it is asking for mistakes. With Metric it is just so much easier and therefore less error prone.
At least in metric everybody knows that the terms Kilo means *1000 regardless of what base unit I'm working in, be it weight, mass, time, velocity, acceleration, voltage, current etc.
you cite BTU, but that is based on Fahrenheit which is in itself a nonsensical uint.
RealScience
not rated yet Dec 01, 2013
The problem with imperial is ... that the larger units are arbitrary multiples which means that there are conversions to be applied when different units are specified


@MIBO - I agree - that's why the first advantage I listed to Eikka was:
1) Metric is based on powers of ten, and humans now almost exclusively use base 10.

and why to you I replied:
Today metric makes more sense ..., and because it is decimalized (except time).


While I agree that most scientists prefer metric units, a major exception is Astronomy, where, for example, distance units like AU, light-years and megaParsecs are much more commonly used than vast numbers of kilometers.
RealScience
2 / 5 (1) Dec 01, 2013
you cite BTU, but that is based on Fahrenheit which is in itself a nonsensical uint.

So Fahrenheit is more nonsensical than Celsius, for which zero is the triple point of an arbitrary liquid and 100 is the boiling point of an arbitrary liquid under an arbitrary pressure?

Kelvin and Rankine temperature scales at least have logical roots on the cold end, but the size of the degree should be based on Joules per degree of freedom per mole of particles (and the gram, and thus the mole, should be based on 10^24 hydrogen atoms, rather than on the density of an arbitrary liquid).

Metric is more convenient than imperial and more consistent than imperial, but it is still based on arbitrary stuff at its roots.

MIBO
not rated yet Dec 01, 2013
@RealScience
I Agree that these units are more commonly used when communicating with Humans, mainly because it makes it something we can sort of imagine, but when computing satellite orbits or flight paths to other planets etc the computations are done in SI uints. When performing a GPS fix these are also always performed in SI units, the orbital parameters in the ephemeris are all expressed in these units.
As for Celsius, it is at least related to something that everybody can measure with reasonable accuracy and based on a metric system, Fahrenheit was based on only 1 measurement that the average person could make, the zero point requires ammonium chloride which is not something readily available, and 96F was defined as body temperature, the system was not even constant because it was re-defined to set the boiling point of water at 212 and the scale was designed because dividing distance by 2 is easy. Zero K is not useful so Celsius seems to be a very good compromise.

RealScience
not rated yet Dec 01, 2013
As for Celsius, it is at least related to something that everybody can measure with reasonable accuracy


@MIBO - Ah - so now you LIKE units based on something that everybody can measure with reasonable accuracy. By that reasoning you should prefer inches and feet to meters!

And after Fahrenheit was standardized at 32 for freezing and 212 for Celsius, it is also based on two points that anyone can measure.

Zero K is not useful so Celsius seems to be a very good compromise

Zero K being absolute zero is extremely useful to anyone dealing with either thermodynamics or cryogenics (I work in Kelvin rather than Celsius whenever I deal with heat engines or entropy). Kelvins also eliminates the degrees symbol, and is thus easier to type in an e-mail.
And the official SI temperature unit is Kelvins, not degrees C, so if you like standards you should use Kelvins, not Celsius.

I'll stand by the four advantages I gave Eikka for preferring Metric to Imperial.
Eikka
1 / 5 (1) Dec 03, 2013
Fahrenheit was based on only 1 measurement that the average person could make, the zero point requires ammonium chloride which is not something readily available


Technically not, since we know what different temperatures in Farenheit are already. You could use the boiling and the freezing point of water to calibrate your thermometer just the same.

And the point of the "arbitrary" size of the Farenheit is that it puts the freezing and boiling points of water 180 degrees apart on the dial, and the human body temperature at 64 degrees from freezing to within 10%, which has numerous practical advantages in actually making the thermometer scales.

And the original temperature scale was NOT defined by using human body temperature, but by contrasting brine and ice with plain water and ice, and human body temp was used to check that you got it right.
Eikka
1 / 5 (1) Dec 03, 2013
I'll stand by the four advantages I gave Eikka for preferring Metric to Imperial.

1.) Everyone counts inches/feet/yards/miles etc. in decimal. The point is moot as long as you stick to a single unit, in which case it all behaves just like metric. You can even use the prefixes if you really want to.
2.) Appeal to novelty is a logical fallacy
3.) Practically everyone and everything has already converged to a single set of measures because there's no real use in having different sizes of the same thing
4.) US customary units are a de-facto worldwide standard regardless, because everything from shipping containers to electronics parts, wire gauges, clothes, rail gauges, building material sizes, televisions (only the French bother to measure theirs in centimeters), even nuts and bolts (but usually not the threads) are made to conform to imperial sizes and tolerances and the numbers they print on the box are actually just rounded up or down to the nearest equivalent in metric.
Eikka
1 / 5 (1) Dec 03, 2013
Especially to the last point, it would be much easier if the industry would just call a 4 inch nail a 4 inch nail instead of pretending it's a 100 mm nail when it really isn't. It's less of a tongue twister at the hardware store.

And if you call it a "ten cent nail", there will be confusion whether you want a ten centimeter nail, or a nail that costs ten cents. See, the metric units have inconvenient and awkward names on top of everything.
RealScience
not rated yet Dec 03, 2013
The point is moot as long as you stick to a single unit, in which case it all behaves just like metric.

I agree with you that the advantages are not intrinsic.
However imperial CURRENTLY does NOT stick to a single unit, whereas metric ALREADY does.
Appeal to novelty is a logical fallacy

The point is not the novelty,but the lack of historical baggage. All liters are the same, not all gallons are the same.
Practically everyone and everything has already converged to a single set of measures

Exactly - it's called metric, or SI.
US customary units are a de-facto worldwide standard regardless
There is considerable truth to this for consumer goods (but not in science), but even there it is mixed: Metric nuts and bolts are truly metric, whereas plywood is 4'x8' even in metric countries.
However 10-penny nails now longer cost 10 cents per hundred (and a planed 2"x4" is conveniently very close to 4 cm x 9 cm).
Eikka
1 / 5 (1) Dec 03, 2013
However imperial CURRENTLY does NOT stick to a single unit, whereas metric ALREADY does.


Yes it does. Nobody ever measures miles in inches or feet of altitude in yards because there's no need to, in the same way that nobody measures gravel in two different pounds. Why would they?

The point is not the novelty,but the lack of historical baggage. All liters are the same, not all gallons are the same.


But since the UK and Australia went metric, there's no other gallons to care about except the US standard gallon.

Metric nuts and bolts are truly metric


The threads are metric, and there exists nuts and bolts that don't have equivalents in imperial, but the actual products use closely matching parts. There's a reason why e.g. car wheel nuts are often 19mm in Europe and 3/4" in the US - they're actually made in the exact same head size to fit the same tool, and simply labeled differently. The same goes for many other common sizes that are actually used.

Eikka
1 / 5 (1) Dec 03, 2013
For example, different sizes of wrenches:

4 mm - 5/32"
8 mm - 5/16"
10 mm - 13/32" (maybe slightly sloppy)
11 mm - 7/16"
12 mm - 15/32"
15 mm - 19/32"
19 mm - 3/4"
23 mm - 29/32"

The tolerances are such that the US size always opens the metric size, but not necessarily the other way around.

The manufacturers prefer to use these sizes because it means they can use the same tools on the same robots on the same production lines to make cars and bicycles and appliances for both European and American markets. The parts are manufactured in such ways that the actual size of the nut/bolt lands within both tolerances.

The only difference I've noticed is on fixing Japanese cars, which also have 14mm and sometimes 17mm bolts, but never on parts that the owner is expected to open.
Eikka
not rated yet Dec 03, 2013
There's also some benefits in measuring different things in different units. When your elevations are in feet, and your distances in miles, you're never going to mistake the two and accidentally program your autopilot wrong.

You also get to use the size of unit that most fits your task. Nuclear physicists don't think of sizes in picometers, they use Angstroms which is defined to be 100 picometers. The energy industry doesn't use Joules, they use Watt-hours. Celsius instead of Kelvin. Bicycle and car tires aren't pumped up to Pascals, they use Bars of pressure. Even the liter falls under this category, because it is not offically a part of the SI. These are all convenience units, which are approved to be used in conjunction with the SI but really have no scientific meaning; if you really were using SI metric you should be drinking cubic decimeters.

It's really no different from using BTUs and gallons and inches, so even the metric people aren't actually practicing what they preach
Jaeherys
not rated yet Dec 03, 2013
Don't forget the use of the metric system in easy calculations of concentrations, dilutions, and other conversions. In biology we calculate 1000s of dilutions and solute concentrations. I can easily do calculations in my head between say nanomolar and micromolar without any problem. Or when converting from molar mass to molarity in a solution, again, it is easily accomplished with simple mental math even though you can be working with numbers that are 10^-6 or 10^-9.