Thoughts On the Chinese Spy Balloon

Updates have been added to this article,  appended below.  These are for 8,  13,  and 14 Feb. 2023.  Also,  one photo was added at the end 18 Feb. 2023.

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I see a lot of activity on the internet about the Chinese balloon that flew over the US.  Most of that crap is just that:  “uninformed speculation” is just a long-winded way of saying “crap”.  Informed speculation (“not crap”) is far better.

Some informed speculation from me:

1. This thing had a forest of antennas and other equipment under it,  about the size of two school buses,  which is why they wanted to delay shooting it down until it was over the ocean.  That's a serious falling debris hazard over inhabited land. 

Speculation:  could this thing have been harvesting data from the Tik Tok software that they have infiltrated into us over the last few years?  Or the Chinese-made microchips that are in just about everything we use today?  Or both?

2. Everybody here wanted to see the thing shot down.  Question is,  how do you actually do that?  Our air-to-air missiles are not designed to track targets of that type.  The gas bag itself would have little or no radar signature,  and little if any infrared signature. 

Such missiles would be more likely to home-in on the equipment hanging underneath the gas bag.  That would have some radar and infrared signatures.  In that event,  it would be more difficult to recover the equipment and determine what it was doing.  The missile would have blown it all to pieces,  not to mention the further damage from impact with the surface.

Puncturing the gas bag with simple gunfire would be a better choice,  but who has airplanes that fly that high anymore?  This thing was reportedly at or above 66,000 feet. Only the U-2 and SR-71 spy planes flew that high.  Neither was ever armed.  Both are now long-retired.

Supposedly this thing was shot down by an F-22 using an AIM-9 Sidewinder.  The aircraft was reportedly flying at 58,000 feet,  which would be just about the top of its flight envelope.  Climbing from there to 66,000 feet would be just about the limits of what a Sidewinder would be able to do.  It would be way out of range vertically for a gun shot,  even if the F-22 had guns.  (Actually it does,  but they may or may not have loaded gun ammo on board for this mission.)

3. Supposedly this is the 4th such incursion by balloon in recent years.  It was just the first seen by the public,  thus making the news and causing a commotion.  But there is a pattern here!  The Chinese would not be doing this to spy on our missile silos and bomber bases.  They do that with satellites.  It's hard-to-impossible to steer a balloon where you want it to go,  anyway.

Speculation:  they were trying to acquire information that is spread diffusely across America,  not any particular point targets.  That lends credence to the notion of intercepting internet information generally,  and Tik Tok or microchip-acquired information specifically.  Such would be preparation for waging cyber warfare.

4. The "right" interceptor for high-altitude balloons like this would resemble the old NF-104.  That would be a modified jet fighter craft with a rocket engine,  an attitude thruster control system,  and air-to-air guns to punch holes in the balloon and let the lifting gas out.  It's been 50 years since we had a thing like that,  and the NF-104 had no guns back then,  being instead a trainer for rocket plane pilots.  It flew multiple times to altitudes in the 90,000-to-125,000 feet range.  Some less heavily loaded weather balloons fly that high.

My suggestion:  modify some F-16’s with a simple rocket engine in the tail like the old NF-104,  plus an attitude control thruster system.  It doesn’t need the heavy radar in the nose anymore,  that weight allowance can go to the modifications.  It already carries missiles,  just make sure it has guns and ammo on board.  (Most of the F-16’s had an M61 Vulcan 20 mm cannon in the left wing root.)

Just keep it simple,  stupid! (“KISS”).  Such a craft can take off within minutes,  and climb to meet the balloon threat within just minutes more.  You can fire at the balloon on the way up past it,  and again on the way back down.  Way cheaper than a surface-launched interceptor missile!

One additional suggestion:  the gas turbine main engine is going to starve for air on the way up in rocket power.  Make sure the modifications include a sure way to restart it on the way down,  and make sure there is no loss of hydraulic power to the flight controls while the engine is not turning.  Those were serious flaws seen with the old NF-104.

This is not a high-tech development.  There is no excuse for not having one flying within just several months.  And it should not be expensive,  either.  After all,  it was fast and inexpensive 50 years ago with the NF-104!

One last thing to worry about:  US spy planes flying near China are unarmed.  They have been subject to Chinese fighter harassment that includes some very unsafe flying practices.  The next step for the Chinese is to start shooting those US spy planes down,  international airspace notwithstanding.  It’s my opinion that those planes need to be armed or escorted,  and the rules of engagement should be to shoot before the enemy gets too close.

Update 8 Feb 2023:  Reports now indicate there was another one over Latin America during this incident,  an earlier one over the US during Biden's term,  and 3 during Trump's term.  These earlier ones were not detected until after-the-fact,  which explains why Trump administration figures say this didn't happen,  when the actual military records say it did.  

What that really indicates is that NORAD did not detect or recognize these balloons for what they were,  until very recently.  Yet detecting intruders over the US is exactly what NORAD is intended to do!  It would appear that nobody expected such an obsolescent technology as a threat,  so nobody was watching for it.  These things don't have much in the way of radar or infrared signatures,  and are visually apparent only in broad daylight,  so they really are a sort of semi-stealth platform.

The mission here may be as much about political ends as anything to with gathering surveillance information.  China has been infamous ever since its communist revolution for bullying behavior to intimidate other nations into submitting to Chinese will.  Now they have a track record of flying surveillance balloons over the US unopposed,  until this last one.  That may explain their outraged reaction to its being shot down.  

The "open skies" precedent set by Sputnik 1 in 1957 applies to satellites and spacecraft considered to be flying in space,  that being defined as above 62 miles (100 km) altitude,  above the sensible atmosphere.  That is why nobody has been trying to destroy other countries' spy satellites.  It very most definitely has never applied to balloons or any other kind of aircraft flying below that altitude,  down in the atmosphere!  Airspace violators have always risked being shot down!  

It does make moral sense to determine if an intruder is a hostile threat or not,  before deciding to shoot it down.  Spy missions intruding into territorial airspace have traditionally been considered hostile threats.  Airliners strayed off course would not be,  although Russia shot one down for straying over its territory at Sakhalin Island a few years ago.  Dictatorships tend to do ugly and immoral things like that,  as we have seen.  

Science missions like a weather balloon straying off course would be hard to identify as such,  but the ground team managing the mission need merely contact the country where it strayed,  to avoid it being taken as a hostile.  That did not happen with any of these Chinese balloons.  So,  that excuse is as flimsy as a straw house in a hurricane.  Do not believe it!

These things apparently had as their prime mission the political end of seeing if they could get away with intruding into US airspace at high altitude unopposed.  Any actual intelligence they could gather would just be gravy.  It would be diffuse information spread across the country,  likely from the internet and the chips that enable so many devices these day.  It would help enable better cyber warfare against us.  Things that connect to the internet can always be hacked!  That's just an ugly little fact of life!

The way for a balloon to avoid being shot down by fighters like the F-22 would be to either increase gas bag size for a given payload,  or reduce payload weight for a given gas bag size,  or both.  That would enable the balloon to fly at significantly higher altitudes,  even above 100,000 feet,  where fighters (and nearly all missiles) cannot reach.  They may try that before they give these missions up.  But like any bully,  they won't stop bullying until smacked in the nose.  

Therefore,  we are going to need a way to shoot these things down at altitudes above 100,000 feet!  Which is exactly why I suggested a mixed-power F-16 as a reprise of the NF-104's capability to conduct vertical zoom flights to altitudes above 100,000 feet.  You don't even need explosive gun rounds,  simple solid slugs will punch holes in a thin plastic gas bag.   

Lasers might work,  except that accurate pointing is required,  and the difficulty and expense of doing that increases exponentially with the range.  The slant range to a balloon target is going to be a few dozen miles.  That's long range,  and it will be difficult and expensive to do.  Besides,  radar and infrared guidance for pointing the laser is not going to work,  and visible light guidance will only work in broad daylight on a relatively clear day.  There is nothing else to use.  That puts us right back to a manned interceptor airplane. 

Solid slug ammo,  even at 20 mm cannon size,  would be cheap at a few bucks each.  Explosive rounds are a few hundred bucks each.  An air-to-air missile is a few hundred thousand bucks (or more),  and a surface launched SAM is a few million bucks.  One capable of hitting targets at over 100,000 feet up,  will be several million bucks or more.

It's a cheap intercept because you recover the plane!  You are only out the price of the fuel,  a payment to the engine overhaul kitty,  the pilot's hazardous duty pay,  and the price of the ammunition used.  The planes I suggested are obsolescent anyway,  and will eventually be going to the boneyard otherwise.  The modifications needed are all well-known,  no development required.  There is no excuse for such a capability requiring a large budget or a long time to emplace.  

You build one or two,  test them,  make the indicated changes and test those to verify them,  then you build a few more examples and field them.  We don't need very many,  but once your mods are verified and you have drawings,  you can always build a few more if you find you need them.  

Plus,  they can serve a dual purpose.  They can help train space plane pilots,  just like the old NF-104 did.  Sierra Nevada may need that,  if they get their manned version of their Dream Chaser space plane flying.   If they do,  others will follow.

Update 13 Feb 2023:  As of this writing,  since the downing of the big Chinese spy balloon 8 days ago,  there have been three more shootdowns:  over Alaska (10^th) and the Yukon (11^th) of much smaller objects at much lower altitude (near 40,000 feet),  plus a small object at 20,000 feet over Lake Huron.  The Alaska and Yukon objects appear to be cylindrical,  and about the size of a small car,  and appear to be floating with the wind.  The Lake Huron object was described as “octagonal with strings hanging from it”.  There is no indication yet of what they really were,  or who put them up there.

What I think we are all seeing is the chaos of NORAD realizing these small radar anomalies that it used to ignore,  really are intruding stealthy objects of some sort.  Suddenly the skies seem to be full of them.  A lot of public figures,  and some military leaders,  are saying noncommittal and sometimes-contradictory things about this issue.  Complicating this further are the recent news stories about investigating other unidentified objects often seen by military pilots.  Refer again to the yellow-highlighted paragraph in the previous update just above.

I don’t think anybody on our side realized just how stealthy a such balloon platform can be for purposes of spying.  But the Chinese,  and maybe some others,  seem to have understood this.  It does make the spy balloon a “cheap” alternative to the spy satellite.  These are the lower altitudes from which better photography can be obtained than from satellites hundreds of miles up,  the main reason we once fielded the U-2 and SR-71 spy planes. 

Higher is more invulnerable from intercept.  Both the Air Force and the Navy have had fighter aircraft capable of reaching 58,000 to 65,000 feet,  for a long time now.  But large balloons,  if lightly loaded for their size,  can fly very high indeed!  The balloon from which Joe Kittinger parachute-jumped in 1960 testing high-altitude bailout equipment,  was flying at about 103,000 feet.  The persons who broke his parachute jump record just a few years ago,  jumped from balloons flying at about 130,000 feet.  The airplanes and air-to-air missiles that we have today simply cannot reach those altitudes. 

If the target identification and beam guidance problems can be handled,  it would be far less expensive to “pop” these balloons with a laser beam.  However,  the slant range to target from the surface is multiple dozens of miles.  Doing this laser shot thing from an airplane near 50,000 or 60,000 feet reduces those beam guidance difficulties,  with a weapon that could still reach a really high-altitude balloon,  when the airborne missiles we have cannot reach such targets.  That does assume the well-guided laser system is a payload light enough,  that the airplane carrying it can still reach 50,000-60,000 feet.  But if the laser system is too big,  the airplane carrying it cannot reach such altitudes. 

Spy craft are traditionally considered to be “hostiles”,  and traditionally subject to being summarily shot down.  It is just as possible to send a small weapon payload by balloon as it is to send a spy payload:  the Japanese tried sending incendiary fire bombs to the US by balloon in World War 2.  It would not be all that easy to tell a scientific payload from a spy payload,  or some kind of weapon payload,  even if one could “eyeball” the thing fairly close up.  That means you have to “eyeball” it really close up!

Many weather balloons are small objects intended to reveal the winds,  with little or nothing in the way of payload suspended beneath.  Others could be very large balloons with large scientific payloads.  Even companies and private individuals can launch such things.  Ethics requires target identification before shooting the thing down.  Dictatorships may ignore ethics,  democracies should not.

My point is that target identification,  required for a yes or no answer to the shootdown question,  may well be the real reason we need an aircraft capable of reaching the balloon at its altitude,  no matter how extreme,  for a close look.  If the balloon is flying nearer 100,000-150,000 feet than 60,000 feet,  then we currently have no airplanes capable of doing that mission,  regardless of any laser or other weapon we might use for the shootdown.  We might not want to shoot it down after all,  depending upon what it turns out to be,  upon close inspection. 

Which dilemma puts us right back to my suggestion of reprising the vertical zoom flight capability to the edge of space,  that we had in the NF-104 decades ago.  That’s currently the only imaginable way to get human eyeballs close to one of these intruders,  for target identification purposes,  at the more extreme altitudes well above 65,000 feet.  The stay time close-by isn’t very long,  but it is much better than nothing!  It might take two flights sequentially,  one to evaluate the target visually for the shootdown decision,  the other to shoot it down,  if that is the decision. 

If you can get that close,  a gun (or a short-range laser) is all that is needed.  Guns we have had for decades.  Airborne lasers,  well,  maybe,  and maybe not.  Gun rounds are cheap compared to missiles,  even small airborne missiles.  I would further suggest using standard 20 mm ammunition,  except replacing the projectiles with scattershot loads,  like a big shotgun shell.  That way,  there would be very little risk to people and things on the ground,  from falling ammunition,  only from the balloon payload itself.

As to the chaos we have seen recently,  consider this.  What we have been watching for all these years,  is intruding airplanes and missiles (or drones).  If stealthy,  the radar return will barely be distinguishable in terms of signal-to-noise ratio.  The doppler would show the higher speeds of aircraft or missile flight.  The radar anomalies previously ignored would show barely-perceptible low radar return and a low doppler-derived velocity,  comparable to wind speeds.  Unless you are actually looking for balloons,  you would ignore targets like this.  And apparently,  we did.

Now that we are looking for such targets instead of dismissing them as “anomalies”,  we are suddenly seeing a lot of them!  Odds are,  most of these are neither spies or other threats.  Quite a lot of them might be things sent up for commercial interests or even private-individuals-for-fun.  Distinguishing the real spies and threats from the harmless stuff so many miles in the air is what will require sending a real pair of eyes very close by. 

If you seriously want to reprise the mixed-propulsion vertical zoom aircraft capability,  here are the design requirements I suggest.  The rocket thrust to aircraft weight ratio needs to be such that thrust equals or exceeds the aircraft weight plus its drag.  Use the lift/drag ratio L/D for high-altitude lift equals weight cruise,  to rough-estimate this as F_th/W = 1 + 1/(cruise L/D).  Use the max gross takeoff weight of the aircraft for this.  You should probably have a turndown ratio equal to,  or exceeding,  3 to 1 . 

Assuming you are zooming upward under rocket thrust at roughly the speed of sound in cold air (about 960 ft/sec),  the vertical distance you need to traverse is target altitude less the altitude at which you start the zoom climb (perhaps 35,000 feet as a guess).  For a target at 150,000 feet,  that would be about 115,000 feet.  The rocket burn time requirement is then roughly 115,000/960 = 120 sec = 2 minutes of burn.  That sets your propellant quantity W_prop required,  from the rocket specific impulse Isp and the design thrust F_th,  as a total impulse requirement:  I_tot = F_th * t_burn = Isp * W_prop.

The zoom aircraft will not need the typical radar and associated avionics for fighting with radar-guided air-to-air missiles.  Removing those gives you the weight allowance you must have,  in order to install the rocket engines and propellant tankage that you need,  plus the attitude thrusters and associated propellant,  that you will also have to install. 

For shooting down the threat,  use the guns or infrared-guided air-to-air missiles (or a laser installation,  if you can afford the weight).  If you cannot afford the weight of the laser on your zoom craft,  your laser installation will have to work from a lower altitude where it actually can be carried. That’s a different airplane design from the zoom craft.

There,  I’ve told you exactly how to get started on reprising a mixed-propulsion vertical zoom aircraft capable of reaching extreme balloon altitudes.  It’s an aircraft modification,  not a new development!  You scab on the rocket engines,  and replace the on-board radar with the propellants and the attitude thrusters.  You keep the gun if it has one,  and any launchers for Sidewinder missiles.  There’s no excuse to spend years and $billions doing this!

Update 14 Feb. 2023:

This is what it looks like to rough-size the items for a mixed-propulsion modification to an F-16C aircraft.  The aircraft weight statement rough-size calculations look like Figure A,  which is the spreadsheet image where I iterated these numbers.  What I assumed for the rockets was IRFNA-jet fuel propellants for the pressure-fed main rocket engines,  and IRFNA-UDMH for the attitude thrusters.  Both IRFNA and UDMH are materials the military has handled in the field previously. 

The pressure-fed main engines are not hypergolic,  and will require something like TEB injection for their ignition.  The thrusters are hypergolic and pressure-fed.  Since the main engines use aircraft jet fuel,  the added propellants include a little bit of UDMH for the attitude thrusters,  and a lot of IRFNA for the main engines and the attitude thrusters.   Part of the rocket systems package is a pump to take the unpressurized aircraft fuel and pressurize it to around 2000 psia for pressure-feeding the rocket chambers.

Figure A – Rough-Sizing the Weight Statement Numbers for a Mixed-Propulsion F-16C

Supporting these numbers are the ballistic sizing results for the main engines (Figure B) and for the attitude thruster “engines” (Figure C).  The main engines have a thrust sizing requirement more-or-less determined by the aircraft weight rough-out in Figure A.  The thrust requirement I used for the attitude thrusters is an arbitrary 500 lb force for any one single thruster.  I assumed the total thruster impulse requirement to be equivalent to one thruster continuously for the entire main engine burn time.  

Figure B – Roughed-Out Ballistic Sizing for the Main Rocket Engines (2)

Figure C – Roughed-Out Ballistic Sizing for Attitude Control Thrusters (Multiple)

The specific impulses I obtained for the main engines and thrusters are close enough to the 300 sec values that I assumed for them in the aircraft weights sizing,  that I did not need to revise those inputs to the aircraft weights sizing.  There are larger uncertainties here than just those values of specific impulse.

The dimensions of the main engine units are not all that large,  and should easily fit as scab-ons to the upper strake surface,  on either side of the vertical fin.  The plumbing and storage vessels for the TEB (tri-ethyl borane) ignition fluid should probably just be a part of each main engine unit.  That allows very easy access for TEB load and unload,  enhancing safety.  TEB is also a material the military handles in the field,  the most recent example being the SR-71 engine/afterburner igniter fluid.

That gets us to the illustration in Figure D of what these aircraft modifications look like,  and where they are located. 

First,  there are considerable avionics equipment items to remove from the nose,  this craft not being expected to ever use radar-guided air-to-air missiles,  or to ever need countermeasures in combat.  Those include the AN/APG-68 radar,  the AN/ALR-56M radar warning receiver,   and the AN/ALQ-213 electronic warfare suite.  Some of my numbers are for “similar equipment”,  and I rounded up slightly to cover removal of countermeasures and countermeasure dispensers elsewhere on the airplane. 

The rocket “pressure plumbing and controls” that replaces the avionics in the nose includes the pressure pump and surge chamber that takes jet fuel from the aircraft tanks and pressurizes it to about 2000 psia for the pressure-fed main rockets.  There’s crudely a 500 lb allowance for all of that in the nose.

The main rocket propellants are stored pressurized in two payloads mounted to the inboard store pylons under the wings,  specifically to be near the aircraft center-of-gravity.  These custom items resemble 500-gallon drop tanks,  much smaller than most stores usually carried on these stations.  Each carries about 450 US gallons of IRFNA oxidizer to support both main rockets and the attitude thrusters,  plus about 3 US gallons of UDMH to support the attitude thrusters.  

Figure D – What the Aircraft Modifications Are,  And Where They Are

I would anticipate (for redundancy) 2 thrusters for nose-up pitch,  2 for nose-down pitch,  2 for nose-left yaw,  and 2 for nose-right yaw,  all located right at the vehicle axis on the nose,  and perpendicular to the surface.  However only 1 such of each pair is actually used.  I would anticipate 4 tangential thrusters for left roll as two opposed pairs (achieving redundancy),  and 4 tangential thrusters for right roll,  also as two opposed pairs.  I would anticipate using all 4 for any given roll impetus.  None are needed for vehicle axial acceleration or deceleration.  That’s a total of some 16 of these small thruster units.

The mission that such a modified aircraft might execute is illustrated in Figure E.  The aircraft operates as a normal jet aircraft until reaching the geographic coordinates of the intercept zone,  whereupon it executes a brief dive to accelerate,  followed by a sharp pullup into vertical ascent,  with immediate rocket ignition.  The jet engine needs a controlled shutdown during this ascent.  The aircraft remains powered by the rockets in the vertical ascent until it reaches the extreme-altitude target,  with the attitude thrusters maintaining its attitude control above about 65,000 feet. 

Time adjacent to the target is only several seconds,  but the range is close enough to make detailed observations with human eyes right outside the canopy.  These would support a shoot-down or no-shoot-down decision,  more-or-less in real time upon arrival near the target.

The aircraft then falls back unpowered,  using the attitude thrusters to put its nose down,  and to maintain attitude control.  Once dense-enough air is reached (probably around 65,000 feet for the F-16C),  the jet engine is restarted,  and the aerodynamic flight controls will again function.  The aircraft then operates as an ordinary jet aircraft,  pulling out of the dive,  cruising back to its base,  and landing.  

Figure E – The Basic Mission This Modified Aircraft Can Execute

The observation flight that supports the shoot-down-or-not decision is not also the shoot-down flight!  There is a second aircraft needed to perform the shootdown function.  If air-to-air laser technology will support it,  this could be a laser-equipped aircraft,  of any suitable type,  operating as a wingman to the mixed-propulsion observation aircraft. 

If laser will not serve adequately,  a second mixed-propulsion vertical zoom aircraft could perform the shootdown,  using either a heat-seeking air-to-air missile (AIM-9X Sidewinder),  or its 20 mm gun,  or both.  It could actually zoom up past the target,  firing two times:  first on passing the target in ascent,  then second on passing the target in descent. 

Again,  the F-16C has a Vulcan M61 20 mm 6-barrel cannon in its left wing root,  and Sidewinder missile stations on its wingtips.  These would not be changed in the zoom modifications.  I would suggest using custom 20 mm ammunition in the gun.  The idea is to make each round a “shotgun shell”,  by replacing the standard projectiles with a scattershot load.  Such spherical scattershot falling back is small enough (and therefore slow enough) to pose almost no hazard to anybody or anything on the ground. 

Update 18 Feb. 2023:  photo added as humor pertinent to recent events.